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STRUCTURE OCTOBER 2023
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BRIDGES
INSIDE: The San Giorgio Bridge
12
West Seattle Bridge Rehabilitation Project 30 The Golden Gate Bridge 34 Bridge Damage in Turkey 44 SPECIAL SECTION
Structural Engineering Resource Guide 77
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by The National Council of Structural Engineers Associations (a nonprofit Association), 20 N. Wacker Drive, Suite 750, Chicago, IL 60606 312.649.4600. Periodical postage paid at Chicago, Il, and at additional mailing offices. STRUCTURE magazine, Volume 30, Number 10, © 2023 by The National Council of Structural Engineers Associations, all rights reserved. Subscription services, back issues and subscription information tel: 312-649-4600, or write to STRUCTURE magazine Circulation, 20 N. Wacker Drive, Suite 750, Chicago, IL 60606.The publication is distributed to members of The National Council of Structural Engineers Associations through a resolution to its bylaws, and to members of CASE and SEI paid by each organization as nominal price subscription for its members as a benefit of their membership. Yearly Subscription in USA $75; $40 For Students; Canada $90; $60 for Canadian Students; Foreign $135, $90 for foreign students. Editorial Office: Send editorial mail to: STRUCTURE magazine, Attn: Editorial, 20 N. Wacker Drive, Suite 750, Chicago, IL 60606. POSTMASTER: Send Address changes to STRUCTURE magazine, 20 N. Wacker Drive, Suite 750, Chicago, IL 60606. STRUCTURE is a registered trademark of the National Council of Structural Engineers Associations (NCSEA). Articles may not be reproduced in whole or in part without the written permission of the publisher.
O CTO B ER 2023
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Contents Cover Feature
12 THE SAN GIORGIO BRIDGE By David Lattanzi, Ph. D., P. E., Ferdinando Cannella, Ph. D., and Mariapaola D'Imperio, Ph. D.
The 2018 collapse of the Morandi Bridge was international news. Completed in 1967, the bridge carried the A10 motorway over the Polcevera Valley in Genoa, Italy.
O CTO BER 2023
Features 30 THE FUTURE OF INFRASTRUCTURE REPAIR
38 WHEN THE GROUND SHOOK
By Clyde Ellis
By Reid Zimmerman, Egemen Sönmez, and Rebecca Collins
For nearly 40 years, the West Seattle Bridge has been a primary route connecting West Seattle to the greater Seattle metropolitan area.
This is the second of a two-part series on the Kahramanmaras Earthquake Sequence which occurred on February 6, 2023 in Turkiye.
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Special Section
2023/24
77 STRUCTURAL ENGINEERING Resource Guide Annual Special Section with resources for structural engineers, including Profiles of some of STRUCTURE’s advertisers and categorized product listings.
Columns and Departments 7 Editorial Office to Residential Conversions – The Opportunities and The Challenges By Andrew Dolan, P. E., S. E.
24 Code Updates 2024 IBC and IFC Mass Timber Changes By John “Buddy” Showalter, P. E., M. ASCE, and Jason Smart, P. E., M. ASCE
8 Structural Influencers James R. Harris, Ph. D., P. E., NAE, F. SEI, Dist. M. ASCE
29 Codes and Standards FAQ on SEI Standards
16 Structural Analysis UHPC/UHPFRC Compressive Strength Tests
34 Iconic Structures The Golden Gate Bridge
By Dr. N. Subramanian, F.ASCE, FNAE
19 Structural Perspective Thoughts on Computer-Based Testing By Orion R. Paul, P. E.
20 Steel Codes A New Code of Standard Practice for Steel Deck By Thomas Sputo, Ph. D., P. E., S. E.
By Jennifer Goupil, P. E., F. SEI, F. ASCE
By Roumen V. Mladjov, S. E., P. E.
44 Structural Observations Observations of the Bridge Damage Caused by the Mw 7.8 Turkey (Türkiye)
56 Structural Collaboration Steel Bridge Design and Construction By Douglas J. Dunrud P. E.
62 Structural Design Building Enclosure Design to Accommodate Wood Shrinkage By Tammy J. Siliznoff, M. S., P. E. (CA)
65 Engineer’s Notebook Shake, Shake, Shake By Erin Conaway, P. E., LEED A. P.
68 Historical Structures 19th Century Mississippi River Bridges #8 By Frank Griggs, Jr., Dist. M. ASCE, D. Eng,. P. E., P. L. S.
By Prof. Robert K. Dowell, Ph. D., P. E.
52 Structural Efficiency Accelerated Bridge Construction (ABC) Benefits By Ahmed Clayiff, P. E.
In Every Issue 3 Advertiser Index
72 SEI Update
70 NCSEA News
74 CASE in Point
Publication of any article, image, or advertisement in STRUCTURE® magazine does not constitute endorsement by NCSEA, CASE, SEI, the Publisher, or the Editorial Board. Authors, contributors, and advertisers retain sole responsibility for the content of their submissions. STRUCTURE magazine is not a peer-reviewed publication. Readers are encouraged to do their due diligence through personal research on topics. O CTO B ER 2023
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EDITORIAL Office to Residential Conversions – The Opportunities and The Challenges By Andrew Dolan, P. E., S. E.
A
s we all know from our experience over the last few years, there has been a change in where we work and how we work. These changes have resulted in a rise in virtual meetings and an increase in the number of people working from home, either full-time or through a hybrid option. As a result, office space is no longer being fully utilized, leading to a decline in the current office occupancy rates compared to 2019. Is not clear when or if this trend will change as companies continue to evaluate their office space needs as leases expire and are renewed in the future. In addition to the office vacancies, there is a housing shortage in the country that is estimated between 5.5 and 6.8 million homes. The housing shortage is a complex issue that has many different layers that affect different groups in distinct ways. However, with demand higher than the supply, the cost of housing for renters and home buyers has increased and is expected to increase in the future. This need for more housing is throughout the country and requires a combination of multifamily, single-family, and affordable housing options. The easy solution for the two pressing issues is to transform under utilized commercial office space into much-needed housing. This approach not only provides relief for the housing crisis, but also helps mitigate the financial strain that vacant offices place on local governments. Historically, these spaces were only occupied during standard business hours on weekdays. By converting the buildings into multifamily residences, the buildings can now be inhabited around the clock. This increased demand for housing has the potential to rejuvenate neighborhoods and stimulate growth in service industries like restaurants and grocery stores. These conversions can greatly contribute to sustainability efforts. When steel and concrete building framing materials are repurposed, there is a substantial decrease in carbon emissions as opposed to constructing a new residential building. The emission saving are due to not needing to create new concrete and steel, not STRUCTURE magazine
needing to demolish the existing building and having the materials hauled away and a reduction in the dust associated with a demolishing a building. What’s more, renovations present a chance to enhance energy efficiency, by being able to increase the R values and install new energy-efficient mechanical systems. Opting to use existing buildings also expedites the project schedule versus the demolition and a new ground-up construction. For all the positive reasons to move forward, there are significant challenges to these projects. All office conversions have the challenge of converting a space that had common bathrooms and maybe a kitchen for an office floor, into individual bathrooms and kitchens for each apartment. Coordinating the number of risers, ductwork openings and cores needed is a major undertaking for the design team. But not all office conversions are equal and each building presents its own unique challenges to the design team and the developer. The design complexity of the projects depends on the era the original building was constructed. Buildings constructed in the late 19th and early 20th centuries are often ideal for conversion because they have high ceilings, plenty of windows, and were designed to allow light and air into almost every space. These features align well with modern building codes that require adequate light and air in residential buildings. However, converting office buildings constructed from the mid-20th century on poses a bigger challenge. With the advancements of air conditioning and electricity, there was no longer a need for office workers to be near windows for light and air. As a result, modern office buildings have a large floorplate with a significant portion of floor space located far from windows. This creates an inefficient layout of the apartments and unusable portions of the floor due to the lack of light and air. The projects we have worked on have tried different solutions for the areas of the floor that could not be converted. Some have used this space as storage or common amenity space, and some have demolished the multiple bays and to create either internal
“blind shafts” or internal lightwells to bring light to for the entire height of the building. In the projects with the “blind shafts” and lightwells, the square footage that was demolished, was matched with new floors added above the existing roof level. These projects required significant upgrades to the lateral and gravity systems with a substantial amount of time and analysis spent on reviewing the new loads imposed on the remaining original structural elements and designing the necessary structural reinforcing. In addition to the structural challenges, local governments have their own concerns and limitations, primarily linked to current zoning laws, parking requirements, and traffic patterns that may change when converting the use of the building. The final obstacle is the financial aspect of these conversions. The office building with low vacancy rates have lost value, but does that make it financially viable to spend money to convert the building from office to residential? Our current conversion projects in New York City will be rented at market rate, which may not be a viable option in other markets. Do local governments look into tax credits or other incentives to encourage owners to convert the building? Do local governments look into using public money if there is a need for affordable housing? In my opinion, these projects are an excellent way to repurpose existing under utilized commercial office space. In order for more of these projects to go forward, we need building owners, local governments and design professionals to work together to solve the engineering, financial and social challenges associated with converting underutilized office buildings to functional residential buildings.■ Andrew Dolan is an Associate Partner at GMS, LLP in New York City. He is a member of the CASE Executive Committee and Chair of the Structural Engineering Guidelines Committee and holds a MS in Civil Engineering from Virginia Tech and a BS in Civil Engineering from Manhattan College.
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structural INFLUENCERS James R. Harris, Ph. D., P. E., NAE, F. SEI, Dist. M. ASCE James R. (Jim) Harris received his undergraduate education in civil engineering at the University of Colorado at Boulder in 1968. After working in consulting in Denver for five years, he earned his MSCE and Ph. D. from the University of Illinois, Urbana in 1975 and 1980, respectively. From 1975-1981 he was a research structural engineer at the National Bureau of Standards after which he returned to professional practice. He established J.R. Harris & Company in 1984. Jim is an active member of several committees that produce national standards for structural engineering practice and is a former chair of the committee that produces ASCE/SEI 7 Minimum Design Loads for Buildings and Other Structures, and its subcommittee for seismic design. He has also served on ACI Committee 318 which prepares Building Code Requirements for Structural Concrete and on the AISC Committees that prepare the Specification for Structural Steel Buildings and the Seismic Provisions for Structural Steel Buildings. He was elected to the National Academy of Engineering for contributions to the development, improvement, and implementation of modern standards for the design of buildings.
How did you become so involved in the development of codes and standards? What really got me deeply into codes and standards work was graduate school. The professor to whom I was assigned as a research assistant was very interested in standards. Less than a year after I showed up there, he left the university and took a position as the director for the Center for Building Technology at what was then the National Bureau of Standards (NBS). He sent NBS money to the University of Illinois to keep me working on his pet project and then hired me once I got through the course work and the preliminary examinations to come and do a dissertation while working on staff at NBS. That's where I started working on various committees. The predecessor of ASCE 7 was a standard known as ANSI A58.1. While I was working at NBS I was put on the seismic subcommittee for that standard; so, I've been working on what is now ASCE 7 since 1979. The work I was doing at NBS was closely related to improving codes for seismic design which meant that I was involved in committees that later became the Building Seismic Safety Council; I've been on those committees ever since. Of all the initiatives that you've been involved in, what's been your favorite or most rewarding? One of my favorites is an R&D project that we did for a local company to develop a new seismic force-resisting system (SFRS) and then get it officially qualified by the ICC Evaluation Service (ICCES). It was the first such approval of an SFRS, and I was fortunate to be in a unique position to accomplish it. I was involved in an applied research project at the Applied Technology Council in the mid-2000s that developed what's now known as FEMA P-695, which is a methodology for validating that an SFRS designed using linear procedures with R factors, overstrength factors, and deflection amplification factors, would actually deliver the kind of performance that we expected. The pass-fail criterion 8 STRUCTURE magazine
developed for that methodology was eventually adopted by ASCE 7. FEMA sponsored that project because they wanted to stimulate innovation: the idea was, “How do we know that some new system is going to perform the way we expect?” I made a presentation to the committee that runs ICC-ES in 2008 as we were wrapping up the work on that project, describing what this procedure was and how it could really help them. It was politely received and promptly ignored. Nine years later, a company in Denver asked what it would take to get their proprietary structural system to work in earthquake country: they wanted to go to California with their system. I described the P-695 process to them and told them that we should go see if ICC-ES would be interested. This time the people at ICC-ES were interested (some personnel had changed, and the context was different). Beyond modifying the proprietary system so its performance would be what is needed, we also had to develop acceptance criteria for ICC-ES that implemented the P-695 methodology and made it mandatory. That was a big step. Besides achieving a qualification for our client’s system, we set the stage so that other systems could be qualified by ICC-ES. What do you think is the biggest misconception engineers have about the development of codes and standards? I think something that practicing engineers probably don't realize is how serious the competition between various material trade associations is in terms of protecting their stake in the market. And sometimes protecting their stake in the market means driving a stake through the heart of a competitor.
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Early in the development of what is now the basis for our seismic provisions, at the then new Building Seismic and Safety Council, we were in the process of taking a set of tentative new seismic building provisions that had been published in the late 1970s as a direct result of the 1971 San Fernando Earthquake and creating recommended seismic provisions. That earthquake destroyed several buildings that were compliant with the then most current model building codes for seismic. It was the opinion of a lot of people shortly after that earthquake that, if we had code provisions that were up with the state of knowledge in the research world, some of these interesting failures would not have occurred. I had the good fortune to be in Taking the grandkids to a memorable event. a position at NBS where I was put in charge of comparing those provisions with the existing standards at the time. changes to the concrete building code coming out of this. I wouldn’t I carried that with me as volunteer work after I left NBS. That be surprised if we make recommendations about condition assessment effort came up with the impacts on the costs of construction and of older buildings and how you go about doing that. engineering design, as well as tweaks that needed to be made to the What have you learned from going around the world to different tentative provisions to get them ready for prime time. One of the places and seeing how they're doing things compared to how we're key tweaks made changed the R factor for special reinforced con- doing things? Are we leading the way or are we behind? crete moment frames to be the same as the R factor for steel special If you interact with Europeans who are very much up on structural moment frames. In the tentative provisions, the R factor was eight reliability, their opinion is that the methods in the Eurocodes are for steel moment frames and seven for concrete moment frames. much more academically correct and that the US is behind the The Portland Cement Association thought that wasn't fair. I was times. My opinion is: “No, actually we're not.” If you delve deeply impressed by the politicking and the vote counting that went on. into what we have in our system here, I think we’re taking a more There's a lot of that, and I don't think practicing engineers know correct approach on implementing risk adjustments to our reliability how much of that goes on behind the scenes. than they are in the Eurocode. A friend who was an academic from South Africa did a comparaHow much does looking at failures influences codes? You were tive study looking at what we were doing in the US and in Canada involved in some of the 9/11 investigations and are currently versus what was in the Eurocodes and he decided that we are getting investigating the Surfside collapse. the same answers, but are getting there a lot quicker and easier than A lot. One of the lessons learned from the Pentagon actually made a the Eurocode, which is very complicated. We have a method that, difference in ACI 318. We bumped up the capacity reduction factor generally speaking, our practitioners are using and that comes up for spirally reinforced columns with respect to tied columns because with reasonably good reliability-based designs. The method in the of some of the things we saw in the performance of the Pentagon, Eurocodes is more complicated. It looks like it's more rigorous in which was a rather normal 1930s era big government building. terms of applications of reliability, but it actually doesn't tie the knots In those days people used spirally reinforced columns because they together on some of the risk adjustments you need to make for difcost less for heavy loads. That's because the code permitted a 25% ferent modes of failure, which we do in the material design codes in bump in capacity for a spirally reinforced column, as opposed to a the US, not in the structural loads codes. tied column. That was enough to more than overcome the increased cost of the fabrication and installation of spiral reinforcement com- What do you think is the biggest opportunity moving forward in pared to ties. ACI basically took spirally reinforced columns out this industry or something exciting and new that you’re looking of business in the building code before I got on that committee: forward to? at some point when strength design was adopted, the two types of There are a lot of things where we are doing much better engineering columns were treated almost the same. There was a small difference today, because of the way we use computers. Many things that were giving a slight benefit to spiral reinforcement, and it wasn’t enough intractable problems 50 years ago are now treated rationally. Today to encourage the use of spirally reinforced columns. we can analytically examine structural performance under a lot of What happened at the Pentagon showed that for unpredictable different scenarios that would have been difficult before. I think it lateral loads, the column with spiral reinforcement is immensely leads to safer and more serviceable buildings, and, in many instances, better than the tied column. And so, we did something in the code more economical buildings. So, I think the future is bright. that encourages the better column. And that comes with a threat: that people will think that structural engineering can become so routine that you can basically put an Do you think the Surfside collapse will lead to changes in the architectural plan into a computer program and have your structural code or have most of the issues been resolved in the evolution of engineering pop out. And you know, there are some circumstances the codes since 1979? where you can do that for some aspects of the design. But in terms Some of both. You know there's been a lot of changes since 1979 in the of how the system as a whole is going to work, you can’t. We’re not way buildings are designed, but I expect we'll see some recommended there and I don’t expect to actually ever see that.■ 10 STRUCTURE magazine
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RobotWash hard at work.
The San Giorgio Bridge A Case Study in Innovation By David Lattanzi, Ph. D., P. E., Ferdinando Cannella, Ph. D., and Mariapaola D'Imperio, Ph. D.
T
he 2018 collapse of the Morandi Bridge was international news. Completed in 1967, the bridge carried the A10 motorway over the Polcevera Valley in Genoa, Italy. The dramatic collapse and deaths of 43 people shocked Europe, particularly an Italian engineering community that prides itself on a long legacy of engineering excellence. Many theories have been put forward regarding the cause of the collapse, ranging from very human lapses in maintenance and judgment to a lightning strike on a primary cable stay. As of this writing, the cause of the collapse is still under investigation. But this isn’t a story about the Morandi Bridge collapse. It’s the story of what came next.
12 STRUCTURE magazine
The Morandi Bridge was a critical link between communities in Genoa and the broader Liguria region of Italy. The loss of the motorway led to a year-long state of emergency and urgent pressure to design and build a replacement bridge as soon as possible. However, this replacement faced a slew of technical and societal challenges. A coastal city, Genoa has been known for its naval prowess for millennia, relying on its steady winds to send ships abroad. The Polcevera Valley serves to amplify these coastal winds, often accompanied by powerful storms. The designers didn’t just need to consider complex environmental conditions but also complex psychological conditions.
Perhaps more than any of us fully realize, civil engineering is an act of trust between builders and the communities they serve. Regardless of the cause of the Morandi collapse, the event shattered the public’s trust in the safety of their infrastructure. It is worth considering historical precedent to understand how designers address the psychological aspects of collapse. One of the most well-known and publicized bridge collapses ever was the Tay Rail Bridge disaster in Scotland. Constructed in 1878, the bridge was a technological marvel of its time. It employed a combination of complex truss latticework and cast-iron materials in the same manner used in the Crystal Palace and Gustave Eiffel’s Massif Central viaducts. But in 1879, only 19 months after opening to the public, the bridge collapsed in high winds, killing the 75 passengers of a rail train crossing at the time. At the time of the collapse, another railway bridge was being Engineers looking over InspectionRobot’s retractable arm design. designed to cross the nearby Firth of Forth. An analysis of the collapse led to a complete redesign of what would be known as the Firth of Forth Bridge. The They would design a team of robots that would be integrated into redesign included an aesthetic emphasis on creating an iconic bridge the bridge itself. One robot, “RobotWash,” would be tasked with that looked indestructible. That bridge is now a UNESCO world cleaning the bridge, particularly the glass barriers and solar panels. heritage and a significant tourist attraction for visitors to Edinburgh. The other robot, “InspectionRobot,” would inspect the ship-like How was Genoa to recreate this process in the 21st century? It structural exterior while serving as a highly visible manifestation would not be enough to make the bridge look sturdy it also needed of structural safety. Most importantly, these robots would work to symbolize Genovese resilience. Renzo Piano was just the man to as part of a team with an integrated structural health monitoring accomplish that. Renzo Piano is, by any measure, one of the greatest system, forming a state-of-the-art digital twin of the bridge. Managers architects working today and has designed countless iconic structures and engineers could dynamically interact with this digital twin in a worldwide, including The Shard in London and the Pompidou Center high-tech command and control center to make maintenance and in Paris. When he won the Pritzker Architecture Prize in 1998, he inspection decisions. Piano’s design was beautiful, but IIT’s was bleedwas compared to Michelangelo and Da Vinci, no small comparison ing edge tech. The design and construction of the robots were done for the Italian national icon. He also happens to be Genovese. Who in partnership between IIT and Camozzi Group, a major producer better to lead the design of the Morandi replacement? of industrial automation systems, and a consortium that included Piano’s design went straight to the point: Genoa has been a sea power SDA (the structural designer), Università Politecnica of Marche (the for millennia. The new bridge would celebrate that remarkable heritage defect detection system designer) and Ubisive (the human machine while instilling a sense of solidity and security. It also had to handle interface designer). the high winds of the Polcevera Valley, and construction speed was Each robot design was a first of its kind. RobotWash needed to paramount, two critical factors for the bridge’s design. The result was traverse the length of the bridge on an integrated rail system, with the new San Giorgio Bridge, with an elliptical profile that evokes a ship a payload of cleaning brushes and accessories, like an automatic car hull while providing optimal wind resistance. Internal to the elliptical wash. Given the similarities, the team at IIT brought in rollercoaster “hull” is a steel box truss design that could be rapidly fabricated and engineers to help with the design. The biggest challenge was the difassembled, reflecting a successful partnership between architect and ference in construction tolerances between rollercoasters and bridges, engineer. The Morandi was a visually dramatic cable-stayed design. which generally differ by order of magnitude. The San Giorgio is sleek, modern, and minimalist. RobotWash was a challenging design, but InspectionRobot required The design is beautiful and efficient, yet it did not address the innovation on an entirely different scale. Again, the high wind environpsychological impacts of rebuilding after a collapse. Not only that, ment and one-of-a-kind structural design meant that commercially but Piano’s design created two significant difficulties. The sound and available inspection technologies weren’t feasible. Eventually, the design wind barriers on the roadway were clear glass, which Piano insisted for InspectionRobot settled on a huge robotic arm that could deliver on so that motorists could take in the beauty of his iconic hometown. a sensor payload of cameras and non-destructive testing equipment Maintaining that beautiful view meant keeping the glass consistently to any location on the bridge hull. The information from these senclean. Additionally, the combination of high winds and the elliptical sors, combined with localization data from the robot, would allow profile of the bridge meant that traditional inspection equipment like the generation of a high-resolution 3D model of the bridge exterior, snooper trucks and even modern inspection systems like drones would which could be continuously analyzed by humans and AI systems back be infeasible. In short, the bridge would be a maintenance headache. at the bridge command center. Just like the design of the bridge, the Since some forensic studies pointed to maintenance problems as the design of InspectionRobot was governed by wind forces. Numerical cause of the Morandi collapse, this was not a trivial concern. simulations of the robot arm showed that it would be subjected to The Istituto Italiano di Tecnologia (IIT) proposed a novel solution. severe Venturi forces and various harmonic effects. It would also O CTO B ER 2023
13
InspectionRobot performing night work.
have to be massive, weighing over 5,000 pounds and telescoping to cantilevered lengths of over 25 feet, making it almost impossible to construct. The answer was to 3D print the robotic arm out of carbon fiber to reduce its self-weight. The 3D printing also allowed the team to design optimal windbreaks along the arm's length to reduce the Venturi effect forces. The complexity of the working environments and the intricate robotic designs meant that both robots needed to operate autonomously with minimal human intervention. InspectionRobot, operating almost continuously, would generate massive amounts
of data that needed to be aggregated and analyzed in conjunction with the integrated sensor system. Engineers and managers needed to be able to engage with the complete set of bridge data interactively and intuitively, so the bridge needed a brain, or at least as close as we’re able to come today. Just off-site from the bridge is a facility that houses the servers and data storage for the bridge. While the idea of a high-performance computer for a bridge is remarkable on its own, the most interesting aspect of the facility is the intuitive digital twin interaction system that allows engineers to visualize bridge data, evaluate the behavior and performance of the robots themselves, engage with AI-driven recommendations, and manage robot activities. It is a remarkable design of human-machine interactivity that sets the standard for the emerging field of digital twin-driven structure management. Here’s the kicker: not only is this one of the most cutting-edge bridges in the world but it was all built in less than a year. While IIT and Camozzi worked furiously on the design and manufacturing of the robots, Fincantieri led the fabrication and construction of the bridge. The 3.5-kilometer bridge was inaugurated in August 2020, a little over one year from construction and almost two years after the Morandi collapse. That any large bridge could be designed and built within that time frame is an engineering achievement. That it could also serve as a technological and architectural paragon is nothing short of remarkable. What does the San Giorgio Bridge mean for the future of our profession? Are we all going to need to become roboticists? The San Giorgio Bridge’s unique circumstances drove the integrated robotics concept, and it is unlikely that every bridge will have its own robot workforce. But drones and inspection robots continue evolving into essential bridge inspection and management tools, as are digital twin systems. While RobotWash and InspectionRobot probably aren’t coming to a highway overpass near you, they show an exciting path forward for robotics, advanced computing, and human-machine interaction in our industry. Our challenge is to figure out how to embrace these ideas to innovate how and where we build and train future generations of engineers who will work with these technologies.■ David Lattanzi, Ph. D., P. E., is an associate professor of civil engineering at George Mason University. A former bridge engineer, he studies how to integrate robotics and artificial intelligence into civil infrastructure systems. He is the current chair of the SEI Bridge Technical Administrative Committee. Ferdinando Cannella, Ph. D. is the Industrial Robotic Facility coordinator at Istituto Italiano di Tecnologia. His research is focused on industrial robotics and AI applied to inspection and monitoring (both for structures and infrastructures recent as well as heritage ones), material manipulation, elastic robot control and reconfigurable grippers. He is the PI of the San Giorgio Bridge robots project and main reference for the I&M at IIT.
Interacting with the San Giorgio Bridge’s digital twin.
14 STRUCTURE magazine
Mariapaola D'Imperio, Ph. D. is a Post Doc at the Industrial Robotic Facility at Istituto Italiano di Tecnologia. The topic of her research is robotics applied to inspection and monitoring of infrastructures and as well as elastic robot control. She is the PM for the InBot group of the San Giorgio Bridge robots project.
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structural ANALYSIS UHPC/UHPFRC Compressive Strength Tests Cylinder vs. cube conversion. By Dr. N. Subramanian, F.ASCE, FNAE
U
ltra-High-Performance Concrete (UHPC) is a concrete class initially developed in the 1990s. UHPC contains no coarse aggregates. When fibers are used in UHPC, it is called Ultra-HighPerformance Fiber Reinforced Concrete (UHPFRC) and offers increased strength and durability. The compressive strength of UHPC may have values exceeding 21,750 psi (Graybeal&Davis, 2008). It Figure 1 Conversion factors for compressive strength obtained from different specimen shapes and sizes for NSC has been found by researchers, especially and HSC (Riedel &Leutbecher, 2017). at the Kassel Universität, Germany, that UHPC can be designed to reach compressive strengths up to 36,250 psi. In addition to its high compressive shown in Figure 1, an NSC cylinder with h/d [in] = 12/6 typistrength, UHPC offers enhancements of high strength concrete (HSC) cally reaches only about 82% of the compressive strength of a such as very high tensile strength (over 2175 psi) and flexural strength 6-inch cube and only about 75% of the compressive strength (over 7250 psi), very high ductility, very high durability to freeze-thaw of a 4-inch cube. These factors increase for HSC, i.e., the difcycles, chloride penetration, abrasion resistance, and carbonation. ference in test results obtained from specimens with different These enhanced properties will result in the overall improved perfor- slenderness is smaller than for NSC. This effect may be attribmance of structures using this material, thus increasing construction uted to the minor increase in concrete compressive strength safety, providing longer service life, and lower maintenance costs. of HSC due to the multi-axial compression stress state (Riedel However, the exceptionally high compression strength of &Leutbecher, 2017). UHPC and UHPFRC will pose issues regarding their strength in laboratory testing. These issues are the limited capacity of Cube vs. Cylinder Strength of UHPC compression testing machines and the surface preparation and UHPFRC Specimen requirement for testing cylinder specimens. The issue of using high-load capacity testing machines could be solved using small specimens (e.g., cylinders with h/d [in] = 8/4 or cubes with side The French guidelines NF P 18-470-2016 propose using cyla = 4 inches).The use of cubes also eliminates the problem of the inder specimens with a 2.8 or 4.4 inches diameter to determine surface preparation requirement of cylinders. Generally, cylin- the compressive strength of UHPC and UHPFRC. In contrast, der specimens are used in the USA, Canada, France, Australia, the Japanese guidelines propose a diameter of 4 inches. In other and New Zealand. However, cubes are commonly used in the countries, such as the USA, a diameter of 4 inches is accepted. UK, Europe, India, and Singapore. For standard concrete and The French Standard classifies UHPC using six strength classes, HSC, the concrete compressive strength test results from cube defined using the characteristic compressive strength obtained specimens are generally higher than cylinders specimens due to from cylinders with h/d = 8.8/4.4 inches or 4-inch cubes, the h/d ratio of 2 of standard cylinders (Subramanian, 2013). assuming a difference of 2175 psi between cylinder and cube Usually, the compressive strength of concrete cylinder specimens strength as indicative value. This results in ratios between cylis considered to have 0.8-0.85 times the compressive strength inder compressive strength and cube compressive strength of of cube specimens. 0.90 (fck,cyl/fck,cube = 18,850/21,025 psi) up to about 0.94 (fck,cyl/ fck,cube = 36,250/38,425 psi). Graybeal and Davis (2008) evaluated 14 compression tests Cube vs. Cylinder Strength Conversion on HSC and UHPC mixtures using premixes without coarse Factors for NSC and HSC aggregate with compressive strengths between 11,600 and 29,000 psi. Methods of producing, curing, preparing, and testFor NSC and HSC, appropriate conversion factors have been ing UHPC are based on the findings of a large-scale research established by several researchers in order to relate results program investigating commercially available UHPC premixes obtained from different specimen sizes to a reference size of (Graybeal,2006). Each series included three sizes of cylinders cylinder or cube (generally cylinder with h/d [in] = 12/6) that (d = 2, 3, and 4 inches) with a slenderness of h/d = 2 and three forms the basis for structural design (EN 1992-1-1:2004). As sizes of cubes (a = 2, 2.78, and 4 inches). Most of the series were
16 STRUCTURE magazine
Type of concrete
NSC (dg = 0.63 in)
HSC (dg = 0.63 in)
UHPC (dg = 0.12 in)
UHPC (dg = 0.02 in)
UHPC (dg = 0.31 in)
Cylinder 150/Cube 100
0.75
0.83
0.90
0.98
0.98
Cylinder 150/Cube 150
0.79
0.84
0.94
–
–
Cylinder 100/Cube 100
0.78
0.84
0.94
0.98
0.98
Cylinder 150/Cylinder 100
0.96
0.99
0.96
1.0
1.0
Cube150/Cube100
0.95
0.99
0.95
–
–
The mean value of compressive strength of concrete is between 3885 and 5180 psi for NSC, between 11,385 and 13,765 psifor HSC, and ranges from 22,025 to 24,505 psi (Series 3), from 23,860 to 24,350 psi (Series 4), and from 23,450 to 23,945 psi (Series 5) for UHPC. Table 1 Ratio of compressive strength between different sizes and with different aggregate sizes of specimen (Riedel & Leutbecher, 2017).
heat-treated, and some were cured in air. The cube specimens were tested with unground-loaded faces. Comparison of mean compressive strengths obtained from 4-inch diameter cylinders (fcyl) and 4-inch cubes (fcu) resulted in conversion factors fcyl/fcu between 0.97 and 1.10 for the UHPC mixtures, i.e., in most cases, the compressive strength obtained from cylinders was higher than the compressive strength obtained from cubes. Especially the UHPC mixtures without fibers showed a high standard deviation of up to 2175 psi, so the scattering of test results superimposed the impact of the different shapes and sizes. Fládr et al. (2013) investigated the relation of compressive strengths of different-sized cubes made with fiber-reinforced HSC and UHPC using mixtures with coarse aggregate. 4-inch and 6-inch cubes with compressive strengths between 14,500 and 26,100 psi were tested in 7 series. For converting 4-inch cube strength to 6-inch cube strength, a factor between 0.85 and 0.99 was obtained by comparing the mean compressive strengths. However, standard deviations of test results of up to 1740 psi might make these results unreliable to accept the impact of specimen size. Kusumawardaningsih et al. (2015) tested UHPC and UHPFRC 4-inch diameter by 6-inch tall cylinders and 4-inch cube specimens. UHPC and UHPFRC specimens used had to mean compressive strengths of 23,987 psi (for UHPC, using cube specimens) and 26,975 psi (for UHPC, using cylinder specimens), 26,540 psi (for UHPFRC with 1% fibers, using cube specimens) and 27,400 psi (for UHPFRC with 1% fibers, using cylinder specimens), and 26,430 psi(for UHPFRC with 2% fibers, using cube specimens) and 26,970 psi (for UHPFRC with 2% fibers, using cylinder specimens). The UHPC specimens that contained no fibers experienced sudden explosive and brittle failures, whereas failures of UHPFRC specimens were ductile and were due to the rupture of fibers. The mean compressive strength conversion ratio between cube and cylinder specimens was found to be: 0.89 (for UHPC), 0.99 (for UHPFRC 1%), and 1.0 (for UHPFRC 2%), respectively. Similarly, the mean compressive strength conversion ratio between cylinder and cube specimens was found to be: 1.12 (for UHPC), 1.01 (for UHPFRC 1%), and 1.0 (for UHPFRC 2%), respectively. These ratios of UHPFRC with 1% fiber and 2% fiber, respectively, are somewhat closer to the conversion ratio found by Riedel and Leutbecher, 2017, Table 1, and as suggested by AMPA (2010), which is 0.95. This finding is interesting as it is opposite to the conversion factors normally used for NSC and HSC, which indicate that cube specimens produce higher concrete compressive strength, as the h/d ratio
of standard cubes is less than cylinders. Also, other researchers found that the shape effect of compressive strengths decreases as the specimen size increases. Additionally, for HSC, the difference in compressive strengths between cylinders and cubes more rapidly disappeared than that of NSC (Yi et al., 2006) According to Dr. Satish Jain, who owns a UHPC/UHFRC plant in India, 2-inch (50 mm) cubes should be sufficient for all internal testing and initial R&D purposes. Using 4-inch (100 mm) cubes for final tests is better, as suggested by the Swiss standards, SIA 2052-2016. According to ASTM C1856-17, the compressive strength of 4-inch UHPC cubes can be used to predict the compressive strength of 3 × 6-inch (75 × 150 mm) UHPC cylinders with an accuracy of +/− 10 percent. The loading rate shall be 145 psi/sec (1 MPa/sec).
Suggested Equation to Predict Strength Neville(2012) suggested the following L’Hermite’s equation to convert cylinder compressive strength to cube compressive strength of concrete:
fcyl = Rfcu
(1a)
Where R is the conversion factor, as shown below:
fcyl R = c 0.76 + 0.2 log10 c 20 mm in MPa
(1b)
fcyl R = c 0.76 + 0.2 log10 c 2900 mm in psi
(1c)
The above equation has been found to predict the cube or cylinder compressive strengths if one of the values is determined or known, particularly for Normal Strength Concrete (NSC) or High Strength Concrete (HSC), with values ranging from 2900 to 14,500 psi (20 to 100 MPa). For UHPC and UHFRC, the following modified conversion factor is suggested by the author: fcyl R = c 0.76 + 0.25 log10 c 25 mm in MPa
(1d)
fcyl mm in psi 3625
(1d)
R = c 0.76 + 0.25 log10 c
A comparison of the proposed equation with the experimental results is given in Table 2. O CTO B ER 2023
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Value of R
fcyl( psi)
Eqn. 1(b)
Eqn. 1(d)
Experimental results from Ref. 8 and 9
NormalStrength Concrete(NSC) 3625
0.78
–
7250
0.84
–
0.78–0.79
HighStrengthConcrete(HSC) 10,150
0.87
–
13,775
0.90
–
0.84
Ultra-High-Performance Concrete (UHPC) 17,400
–
0.93
–
21,750
–
0.95
0.94–1.12
This problem could be solved using small specimens (e.g., cylinders with h/d [in] = 8/4 or cubes of 4 inches).The use of cubes also eliminates the problem of the surface preparation requirement of cylinders. Several researchers have tested UHPC and UHPFRC cylinders of 4-inch diameter and 8-inch tall, and 4-inch cube specimens. Some of these results have been presented. A new equation to convert cylinder compressive strength to cube compressive strength has been suggested. This equation has been compared with the available experimental results and found to give satisfactory results; for UHPC and UHPFRC, the cube and cylinder strengths are almost the same.■ Full references are included in the online version of the article at STRUCTUREmag.org.
Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) 23,925
–
0.96
0.98–1.01
26,825
–
0.98
–
Table 2 Comparison of the proposed formulae with the experimental results.
Summary and Conclusions Ultra-High-Performance Concrete (UHPC)and Ultra-HighPerformance Fiber-Reinforced Concrete (UHPFRC)are increasingly used due to their increased strength and durability advantages. Available compression testing machines cannot be used to test standard 6-inch diameter and 12-inch high cylinder or 6-inch cube specimens, as their capacity will be exceeded.
Dr. N. Subramanian, Ph. D., F. ASCE, FNAE, is a consulting engineer living in Gaithersburg, MD. With a doctorate from the Indian Institute of Technology, Madras (IITM), he also worked in Germany for two years as an Alexander von Humboldt Fellow in TU Berlin and Hochschule der Bundeswehr (Now Universität der Bundeswehr), Munich; He has over 46 years of professional experience in consultancy, research, and teaching. He has designed more than 800 projects. Dr. Subramanian has authored 25 books and more than 300 papers. He is a Member/ Fellow of several professional bodies. He was vice president of the Indian Concrete Institute and the Association of Consulting Civil Engineers (India). He is a recipient of several awards and serves on the Editorial/Review committees of several journals.
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structural PERSPECTIVE Thoughts on Computer-Based Testing A young engineer’s perspective on how computer-based testing can impact the engineering profession. By Orion R. Paul, P. E.
C
hange is scary, and so is the PE Structural Exam. Will changing the PE Structural Exam be a Change is always scary, but engineers adapt; nightmare? Moving the exam from a paper and pencil format to a computer-based testing (CBT) approach they solve problems; they overcome difficulty has caused quite a stir in the profession; however, it might not be as bad as has been hyperbolized. These to achieve goals. They’ll do the same when it changes will have a direct impact on the engineering profession, especially on young engineers like me. comes to licensure examinations. While there are concerns and room for improvement, these modifications could serve as a way to improve the examination process and provide a more achievable path towards S. E. licensure. The new exam will be administered in four parts instead of two, and the (NCEES) has made it clear that eliminating outside materials will make for overall duration will be increased from 16 to 21 hours. The current breadth a more secure test by preventing examinees from copying down questions and depth sections will be broken into their own tests, and each part will and divulging them to others. While the goal is commendable, it’s a radical be graded individually. Although it will increase the total testing time, the departure from how the exam has existed and how engineers operate on individual sitting time will decrease from 8 hours each to 5 hours for the a day-to-day basis. Homemade quick reference manuals are ubiquitous breadth sections and 5.5 hours for the depth sections. While some may prefer in the profession. I’ve never met a principal that didn’t have a weathered, to “rip the bandage off,” breaking the exam into smaller pieces should help coffee-stained packet of papers that covered everything from concrete cover reduce the burnout currently felt in the afternoon portion of an eight-hour requirements to steel limit states in a concise, easily accessible format. If the exam. While the exam as a whole is getting longer, the individual tests will concern has to do with examinees leaving with sensitive test information, be made shorter and more manageable. The exam material is not getting there could be a way to both maintain security and provide test takers with easier, nor should it. Only the testing environment is. If the examination the opportunity to bring in outside reference material. Examinees could bring process can determine if someone has the knowledge and skills needed to in a disposable packet of quick references and be required to leave it at the be a structural engineer, then it’s doing its job. test center for disposal when they check out. Alternatively, examinees could This split into four separate sessions will also benefit test takers in how it is upload a PDF reference ahead of time for use during the exam. There are graded. Whereas in the current format a bad performance in the afternoon options that could work. NCEES could and should make these changes. A can negate a good morning, now each test will stand on its own. Subdividing closed-book test in an open-book world denies the reality of the profession. the test provides additional safety fuses and will help to avoid full retakes. Structural engineers are not alone – other professions face similar hurdles Trying to get four days off from work will cause added challenges. While to licensure. Architects must pass the Architect Registration Examination the breadth section of the new exam will be offered throughout the year and (ARE) which is a CBT exam consisting of six tests totaling 21 hours. The provide for more flexibility, employers should recognize the value in taking cost is nearly identical. The National Council of Architectural Registration such a specialized exam – one that will force their employees to be better Boards (NCARB) recently noted that from 2011 to 2020, the number of engineers with broader knowledge bases and deeper understandings of the licensed architects increased by 17%, compared to a 6% growth of the U.S. codes and calculations that make up their work. Four days is an inconvenience, population. Much like architects, it’s unlikely that the change in the PE but it is only temporary. Hopefully as the exam becomes more established Structural Exam will cause masses of students to switch majors and hordes of and the question banks increase, the depth section will also be available young engineers to change professions. If someone is determined to pursue throughout the year. Even further down the line, it would be beneficial to licensure, they will. both building and bridge engineers to separate the exam based on horizontal I may be an optimist, but I don’t think that the arguments foretelling great or vertical concentration. harm to the profession are based in fact. Change is always scary, but engiOne of the best parts of the transition will be the increased availability of neers adapt; they solve problems; they overcome difficulty to achieve goals. testing locations. This change will make it easier to get to the exam site and They’ll do the same when it comes to licensure examinations. I’ve talked to could eliminate the need for multi-day trips involving travel and hotels. a good number of young engineers and engineering students through the Having all the reference materials and codes on the computer will eliminate Structural Engineers Association of Massachusetts (SEAMASS), the NCSEA the need to lug heavy suitcases filled with books and the possibility of inad- Summit, and career fairs: they are some of the most determined people I’ve vertently forgetting a reference. These changes will make the exam process met. They’re hungry for a challenge and ready for the profession. Changing easier and help reduce stress on exam day. the exam format is not going to hold them back.■ While the prohibition on outside reference materials will make it easier to Orion Paul is a Project Engineer at L.A. Fuess Partners in Boston, MA and currently get to the exam site, it could create a hardship for test takers in the exam serves as the Young Member Group President in his local NCSEA chapter. room. The National Council of Examiners for Engineering and Surveying O CTO B ER 2023
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steel CODES A New Code of Standard Practice for Steel Deck Creating quality in steel deck construction using familiar practices. By Thomas Sputo, Ph. D., P. E., S. E.
T
he Steel Deck Institute (SDI) has recently published a new 2023 the same practices as the AISC Code with modifications as required Edition of the SDI Code of Standard Practice for Steel Deck. to consider the differences between fabricated structural steel and This edition is unique because it is a completely revised edition, steel deck. And third, the SDI would develop the Standard as a and this is the first version developed as a consensus standard under consensus standard under ANSI rules, similar to how the AISC ANSI guidelines. The SDI Code of Standard Practice for Steel Deck, Code is also an American National Standard (ANS). ANSI/SDI COSP-2023, is an American National Standard that The decision to pursue making the SDI Code an ANS was not made codifies generally accepted industry practices for designing, selling, lightly. Doing this required the SDI to give up approving changes to purchasing, manufacturing, and installing steel deck. the submitted document. At the end of the consensus process, the The evolution of the SDI Code of Standard Practice (the Code) has SDI had only two options: to accept the Code as approved by the followed the path of other SDI Standards. The SDI has published consensus body in total or not to accept the Code. The SDI Board a Code of Standard Practice for over 50 years. The SDI wrote these acknowledged the advantages of having the Code being a consensus earlier editions internally without input or approval from other document, reviewed, improved, and approved by a broad-based, interests. These earlier Codes were written to be fair to the affected balanced body of experts representing manufacturers, constructors, parties but were not reviewed or approved by an outside body. deck installers, engineers in private practice, and those from allied The SDI has been an ANSI Accredited Standards Developer since industries. The advantage of having the Code become a consensus 2004, and the first editions of design Standards for Roof Deck (RD), document will be a wider acceptance of the Code within the design Non-Composite (NC), and Composite (C) decks were published and construction communities. in 2006. These 2006 design Standards were an evolution of longstanding SDI specifications provided to the design industry for use The scope of the Code, as written in Section 1, is as follows: in project construction specifications. These design Standards were updated and revised in 2010/11 and 2017 and consolidated into “In the absence of specific instructions to the contrary in the Contract a single Standard for Steel Deck (ANSI/SDI SD-2022) in 2022. documents or the Sales contract, the trade practices that are defined Other SDI Standards which supplement the Design Standards are in the Steel Deck Institute Code of Standard Practice for Steel Deck the Standard for Quality Control and Quality Assurance (ANSI/SDI (herein referred to as the Code) shall govern the design, sale, purchase, QA/QC), written and approved as an American National Standard manufacture, and installation of steel deck. This Code shall govern in 2011, with revisions in 2017 and 2022, and the Test Standard for Composite Steel Deck-Slabs (ANSI/SDI T-CD), also in 2011 with revisions in 2017 and 2022. Starting with the 2010/2011 Standards revision cycle, the SDI has sought to align and coordinate provisions of its standards with those of other standards developers. One of my personal “operating procedures” is “Plagiarism is the sincerest form of flattery.” While I say this tongue-in-cheek and always ask permission to use others’ work, the basic thought process is to seek unity between similar processes. Why not take advantage of the similarity when two standards require the same process or a process that only differs where the specific material or process is required? When it came time to consider revising the 2017 SDI Code of Standard Practice for Steel Deck to coordinate with the 2022 Standards, the SDI made three significant decisions. First, the next edition would use substantially the same organizational format as the AISC 303 Code of Standard Practice for Steel Buildings and Bridges; second, to the greatest extent possible, the SDI Code would use Deck stored on site prior to installation.
20 STRUCTURE magazine
Floor deck bundles properly staged for installation.
where building codes, Owner’s Designated Representative for Design’s plans, and specifications or contracts are incomplete or unclear. There shall be no conflict between this Code and any legal building regulation; it shall only supplement and amplify such laws. Unless specific provisions to the contrary are made in a contract for the purchase and/or installation of steel deck, this Code is understood to govern the interpretation of such a contract.” This will look familiar to those familiar with the AISC Code because it is the same as the AISC language, modified to apply to steel deck construction. The SDI Code uses the same basic terminology as AISC 303 for terms such as Owner’s Designated Representative for Design and Inspector. However, some terms, such as erection documents, are modified to installation documents to reflect general industry practice. The definitions section of the Code is critical because it defines many steel deck industry terms that are particular to steel deck construction and are not used in either the AISC Code or the AISC Specification for Structural Steel Buildings.
Erected or Installed? There are differences in terminology between structural steel and steel deck. 1. Structural steel is “fabricated” from a manufactured product (e.g., rolled steel shapes.), whereas steel deck is “manufactured” from coils of sheet steel. 2. Structural steel is “erected,” whereas steel deck is “installed.”
Therefore, the SDI uses the terms manufactured and installed within the Code and its documents. And the Code uses the term Production Documents instead of
fabrication or shop documents. Production Documents: Digital models, drawings, diagrams, or schedules depicting the steel deck and accessories produced for the specific project. The production documents are what are minimally needed to manufacture the deck. They may consist only of a tabular schedule that lists the deck profile, thickness (gage), finish, steel grade, and deck panel lengths to be produced. This differs significantly from the detailed fabrication drawings needed to produce fabricated structural steel.
The General Provisions and Scope Section 1 of the SDI Code is substantially the same as AISC 303, with terms modified to reflect steel deck construction. Defined terms that are specific to deck construction are added. Subsections are added to address shear connectors installed through the steel deck, fireproofing, temporary shoring for floor deck receiving concrete, and deck support. Another subsection addressing manufacturer standard materials and details is included to address variations between deck products supplied by various manufacturers.
What are Deck and Accessories? Section 2 uses the same format as the AISC Code, which lists the materials which are considered to be steel deck or steel deck accessories supplied as part of the steel deck package and those items which are excluded unless otherwise added to the sales contract between the seller and the purchaser. This should reduce disagreements about what should be included or not included in the steel deck package. O CTO B ER 2023
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Selling and Buying Steel Deck The sale and purchase of steel deck has regional differences. In some locations, the manufacturer may sell deck to the structural steel fabricator, who includes deck in their package. In other regions, the manufacturer may sell deck to a broker who then sells deck to a structural steel fabricator, the Owner’s Designated Representative for Construction (ODRC) (as defined by both the SDI and AISC Codes), or the Owner directly. There are a lot more options available for deck than for fabricated steel. Therefore, the Code defines these entities specifically.
Buyer: The entity that purchases the steel deck from the seller. This is usually the steel fabricator, general contractor, the construction manager, or similar authority at the job site. Manufacturer: The entity engaged in the production (manufacture) of steel deck from sheet steel. Seller: The entity engaged in the sale of steel deck to the buyer. The seller in most instances is also the manufacturer, but it may be another entity, such as a broker.
Floor deck ready for concrete placement.
The seller could be the deck manufacturer, a broker, or sometimes a service center. Likewise, the buyer of deck can be one of several entities.
Some Concrete Information That You Can Use
This is where the SDI Code should seem familiar. The SDI Code has adopted the approval process details of the AISC Code. It makes sense that the structural engineer and the ODRC should be comfortable using the same process for these steel products. The SDI adopts the same definitions for Documents, Drawings, and Models as AISC. This is the first time SDI has specifically included digital documents, including models, within the SDI Code. Digital documents are the same as AISC’s usage, which should help coordinate between the steel frame and deck. The SDI Code adopts the same process for RFI processing as AISC as an example of sincere flattery. Why reinvent the wheel when someone else has a perfectly good wheel we can copy?
Concrete is placed on non-composite (form) deck and composite deck. Because this is an integral part of steel deck floors, the SDI Code includes a Section 11 that applies to concrete design and placement on steel deck. This section sets the responsibility for the design of the concrete with the Owner’s Designated Representative for Design (ODRD), usually the structural engineer, and the responsibility for the means and methods for placing the concrete on the ODRC. This standard practice reflects the proper assignment of risk to the entity best able to control the risk. Once deck leaves the manufacturer and the deck is installed, neither the seller, manufacturer, nor installer is in a position to affect the concrete placement. The requirement to clear the deck of debris before concrete placement includes a user note referencing the ANSI/SDI SD Standard that permits broken stud ferrules to remain on the deck surface.
Primer, Primer Paint, or Shop Coating
Summary
Words have meanings, and sometimes a commonly used word may be misapplied, either by lack of knowledge or occasionally by those with malicious intentions. The SDI does not endorse the use of the words “primer” or “primer paint” in its documents but instead uses the term “shop coating,” which is defined as a temporary coating intended to protect the steel deck under normal atmospheric conditions for a limited period of time. It is not intended to be a permanent coating, nor to prevent rust when improperly stored on the job site, and is not guaranteed to be compatible with any specific finish paint. Some individuals have twisted the word “primer” to infer “Prime Quality” and expect unrealistic coating performance. Additionally, the Code explains that the manufacturer is not expected to repair abrasions or nicks to the shop coat. It is also unnecessary to repair the coating or galvanizing at welds unless exposed to a corrosive environment or otherwise required by the contract documents. By the way, if you want a finish paint coat to be applied to the steel deck, it should be field applied by the painting contractor, and leave the manufacturer, seller, and erector out of this!
This article is a very brief summary of the basis of the new SDI Code and some of the differences from the AISC Code that was used as inspiration for the new SDI Code. The SDI Code of Standard Practice for Steel Deck (ANSI/SDI COSP-2023) is available for free download from the SDI website at www.sdi.org. You are encouraged to download and read the Code and to incorporate the Code within your construction specifications!■
The Approval Process and RFIs
22 STRUCTURE magazine
Thomas Sputo, Ph. D., P. E., S. E., is Vice-President of Sputo and Lammert Engineering, LLC in Gainesville, FL, and the Technical Director of the Steel Deck Institute. Additionally, he is a Senior Lecturer Emeritus at the University of Florida, where he taught structural design for over 20 years. He has over 35 years of experience in varied areas of structural design, including specialty engineering of manufactured components. He is a licensed Professional Engineer or Structural Engineer in 13 states and a Special (Threshold) Inspector in Florida. Tom may be reached at (tsputo50@gmail.com).
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code UPDATES 2024 IBC and IFC Mass Timber Changes
Fire research supports increased exposed ceilings and modified separation distance between mass timber elements. By John “Buddy” Showalter, P. E., M. ASCE, and Jason Smart, P. E., M. ASCE
I
n the 2024 International Building Code (IBC) and 2024 International Fire Code (IFC), several changes were made to mass timber provisions, including the following: • The allowable unprotected mass timber area on the ceiling for Type IV-B construction is increased from 20 percent to 100 percent of the floor area in any dwelling unit or fire area • The minimum 15-foot separation distance between unprotected mass timber elements now only applies to the distance between unprotected areas on walls • Item 3 of IBC Section 602.4.4.3 was changed to clarify that protection only needs to be applied to combustible surfaces in Type IV-HT (heavy timber) concealed spaces • Clarification that construction sequencing requirements for the protection of mass timber (a) (b) elements during construction do not apply to the minimum 1-inch-thick “noncombustible Figure 1 Fire tests confirmed the performance of 100 percent exposed ceilings for Type IV-B construction. Courtesy of RISE Fire Test Report 2021:40 – M.2 photos 45 & M.1 center photo. material” required on mass timber floors 2024 IBC and IFC code text is shown below for 1.2. Unprotected portions of mass timber walls, including attached each topic, with changes identified in strikethrough/underline format. columns, shall be permitted and shall be limited to an area less Only a portion of the total number of code changes is discussed in than or equal to 40 percent of the floor area in any dwelling this article. More information on IBC and IFC code changes can be unit within a story or fire area within a story. found in the 2024 Significant Changes to the International Building 1.3. Unprotected portions of both walls and ceilings of mass Code and 2024 Significant Changes to the International Fire Code, timber, including attached columns and beams, in any available from the International Code Council (ICC). dwelling unit or fire area shall be permitted in accordance with Section 602.4.2.2.3. 2. Mass timber columns and beams that are not an integral Type IV-B Unprotected Mass Timber Area portion of walls or ceilings, respectively, shall be permitted to be unprotected without restriction of either aggregate area or The following revisions were made to 2024 IBC provisions which separation from one another. permit a certain percentage of unprotected mass timber in Type IV-B construction. Justification for the change and several application 602.4.2.2.3 Mixed unprotected areas. (No change to textÉ) examples follow the revisions shown below. 602.4.2.2.4 Separation distance between unprotected mass timber elements. In each dwelling unit or fire area, unpro602.4.2.2.2 Protected area. Interior faces of mass timber eletected portions of mass timber walls and ceilings shall be ments, including the inside face of exterior mass timber walls not less than 15 feet (4572 mm) from unprotected portions and mass timber roofs, shall be protected in accordance with of other walls and ceilings, measured horizontally along Section 602.4.2.2.1. the ceiling and from other unprotected portions of walls Exceptions: Unprotected portions of mass timber ceilings and measured horizontally along the floor. walls complying with Section 602.4.2.2.4 and the following: 602.4.2.3 Floors. The floor assembly shall contain a non1. Unprotected portions of mass timber ceilings and walls comcombustible material not less than 1 inch (25 mm) in plying with one of the following: thickness above the mass timber. Floor finishes in accor1.1. Unprotected portions of mass timber ceilings, including dance with Section 804 shall be permitted on top of the attached beams, shall be permitted and shall be limited to noncombustible material. Except where unprotected mass an area less than or equal to 20 100 percent of the floor timber ceilings are permitted in Section 602.4.2.2.2, The the area in any dwelling unit within a story or fire area within underside of floor assemblies shall be protected in accordance a story. with Section 602.4.1.2.
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Justification The ICC Board of Directors created the Ad-Hoc Committee on Tall Wood Buildings (TWB) in 2015 to explore the science of tall wood buildings and develop code change proposals to introduce provisions for this new construction type. Accordingly, numerous code changes regarding tall mass timber buildings were incorporated in the 2021 IBC. When the Figure 2 A separation distance of 15 feet between unprotected mass timber elements is only required between walls. TWB fire research program was being Courtesy of 2024 Significant Changes to the International Building Code. developed, a determination was made regarding how much ceiling area, wall area, and combinations scope of the application of fire sprinklers or fire alarms. Additional of the ceiling and wall areas could be left exposed during those revisions to the exceptions of Section 602.4.2.2.2 prohibit multitests. Fire performance characteristics of mass timber materials ple-story floor areas from being used to determine the allowable available at the time, coupled with limitations in the test lab’s exposed mass timber in ceilings and walls in multi-level dwelling physical equipment (exhaust hood and exhaust duct connec- units and fire areas. The prohibition was deemed necessary because tor), restricted the amount of mass timber material that could the fire testing used to justify the mass timber provisions was not be exposed during the fire tests, leading to a conservative based on a multiple-story floor area. Further, a single-story or test protocol which, for ceilings, became 20 percent of the multi-story dwelling unit within a tall wood building constructed floor area. A more recent test series, utilizing code-compliant of Type IV-B construction will be separated from adjacent dwelling CLT qualified under ANSI/APA PRG 320-2019: Standard for units with fire-resistance rated construction with ratings as low as Performance-Rated Cross-Laminated Timber, has justified an ½ hour; and non-residential tenant spaces are not required to be expansion of that allowance to 100 percent of the floor area. separated from adjoining tenant spaces with fire-resistance rated Revisions to the 2024 IBC are based on fire research conducted assemblies. This change will preclude the total aggregate floor at the Research Institute of Sweden (RISE) (Figure 1). These area of a multi-level dwelling unit or fire area from being used fire tests demonstrated that increased unprotected mass timber to calculate Type IV-B exposed mass timber areas, which could areas on ceilings and walls can be safely implemented while still have theoretically been applied to only one level. Examples 1 and achieving the TWB Committee’s original fire safety performance 2 show the application of these new provisions. objectives. Specifically, RISE Tests 1, 2 and 5 involved 100 For Type IV-B construction, the 2021 IBC requires the underpercent unprotected mass timber ceilings. RISE Tests 2 and 5 side of mass timber floor assemblies to be protected following also had unprotected mass timber areas on the two opposing the provisions for Type IV-A construction (the last sentence in side walls, equivalent to 78 percent of the floor area. Although Section 602.4.2.3 points to Section 602.4.1.2). However, Section the data also justified a higher percentage of unprotected mass 602.4.1.2 does not permit any exposed mass timber. This conflicts timber wall area, the current value of 40 percent is unchanged with Section 602.4.2.2.2, which allows some limited exposed mass for the sake of conservatism. These tests exhibited satisfactory timber. The change to Section 602.4.2.3 eliminates the conflict performance in that no significant fire re-growth was observed, by clarifying that the reference to Type IV-A construction does and temperatures within the compartment decreased continu- not apply to the unprotected portions of mass timber permitted ously from the time of the fully-developed phase until the end for Type IV-B construction under the exceptions to 602.4.2.2.2. of the four-hour test. In addition to having 100 percent of the mass timber exposed on the ceiling, all five RISE tests also included an exposed glulam beam integral to the ceiling (see Example 1 Figure 1b). This data could be employed to justify exceeding the prescriptive limit of exposed mass timber on the ceiling, thereby allowing for exposed beam faces on beams attached to In this example, a two-level dwelling unit is 30 ft × 30 ft, a fully exposed ceiling, where alternative designs and construc- having floor areas of 900 ft 2 each and ceiling heights of 10 tion methods are used. ft. Section 602.4.2.2.2, Exception 1.3, permits both exposed RISE tests also indicated that the minimum required separation wall and ceiling areas within each story of the dwelling unit distance of 15 feet between unprotected mass timber elements, pre- when the configuration meets the mixed unprotected area scribed by Section 602.4.2.2.4, is only necessary between exposed requirements of Section 602.4.2.2.3. IBC Equation 6-1 for areas on walls (Figure 2). In RISE Tests 2 and 5, the intersection evaluating the combined area of exposed walls and floors is between an exposed wall and an exposed ceiling showed continual used to calculate maximum areas. Using the graphics below decay without significant fire re-growth during the decay phase with proposed dimensions for exposed mass timber elements, for the full duration of the 4-hour test. This justified a change to determine compliance for each story. limit the minimum 15-foot separation distance requirement to For story 1: apply only to exposed mass timber areas on the walls, whereas the Utc = 15 ft × 30 ft = 450 ft2 previous provision applied to exposed mass timber areas on both Uac = 900 ft2 × 1.0 = 900 ft2 the ceiling and the walls. Utw = 18 ft × 10 ft = 180 ft2 A fire area is defined by a building designer and is used to limit the Uaw = 900 ft2 × 0.40 = 360 ft2 O CTO B ER 2023
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Applying these values to IBC Equation 6-1: (450/900) + (180/360) = 0.5 + 0.5 = 1.0 ≤ 1.0, which is compliant. For story 2: Utc = 10 ft × 30 ft = 300 ft2 Uac = 900 ft2 × 1.0 = 900 ft2 Utw = 24 ft × 10 ft = 240 ft2 Uaw = 900 ft2 × 0.40 = 360 ft2 Applying these values to IBC Equation 6-1: (300/900) + (240/360) = 0.33 + 0.67 = 1.0 ≤ 1.0, which is also compliant.
Example 1 – Story 1 Courtesy of 2024 Significant Changes to the International Building Code.
Example 2 It would not be compliant to use the sum of calculated allowable exposed mass timber areas from a multi-story dwelling unit and apply these results to only one story. The graphic below illustrates this violation, where the total allowable exposed mass timber areas calculated from both stories of the dwelling unit in Example 1 are Example 1 – Story 2 Courtesy of 2024 Significant Changes to the International Building Code. applied to one floor only. Utc = 30 ft × 30 ft = 900 ft2 electrical, mechanical, fire protection, or plumbing materials Uac = 900 ft2 × 1.0 = 900 ft2 and equipment permitted in plenums in accordance with Utw = 36 ft × 10 ft = 360 ft2 Section 602 of the International Mechanical Code. Concealed Uaw = 900 ft2 × 0.40 = 360 ft2 spaces shall comply with applicable provisions of Section 718. Applying these values to IBC Equation 6-1: Concealed spaces shall be protected in accordance with one or (900/900) + (360/360) = 1.0 + 1.0 = 2.0 > 1.0 more of the following: This solution would not be permissible because the sum of 1. The building shall be sprinklered throughout in accorratios of the actual exposed area to the allowable exposed area dance with Section 903.3.1.1 and automatic sprinklers within the story in question exceeds 1.0. shall also be provided in the concealed space. 2. The concealed space shall be completely filled with noncombustible insulation. Concealed Spaces 3. Combustible surfaces within the concealed space shall be fully sheathed with not less than 5/8-inch Type X The following change to 2024 IBC provisions for concealed spaces gypsum board. in Type IV-HT construction clarifies that protection only needs Exception: Concealed spaces within interior walls and partitions to be applied to combustible surfaces. with a 1-hour or greater fire-resistance rating complying with Section 2304.11.2.2 shall not require additional protection. 602.4.4.3 Concealed spaces. Concealed spaces shall not contain combustible materials other than building elements and
Justification
Example 2 – Story 1 of 2 Courtesy of 2024 Significant Changes to the International Building Code.
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Concealed spaces were not permitted in traditional heavy timber construction up through the 2018 IBC. Provisions for concealed spaces in Types IV-A, IV-B, IV-C, and traditional Type IV-HT construction were introduced in the 2021 IBC, with specific requirements for their protection. The alternatives for Type IV-HT are the same protection required for concealed spaces in NFPA 13 Standard for Installation of Sprinkler
Systems, except that Option 3 of IBC Section 602.4.4.3 is slightly more restrictive because 5/8inch Type X gypsum is required. In concealed spaces, only combustible surfaces must be protected under Option 3 of Section 602.4.4.3. For example, if a concealed space is created with steel stud framing and heavy timber elements, only the heavy timber surfaces inside the concealed space need to be sheathed with 5/8inch Type X gypsum board, not the steel studs on the interior of the concealed space (Figure 3).
Mass Timber Floor Protection The following changes to the 2024 IFC clarify that construction sequencing requirements for application of noncombustible protection on mass timber elements during construction do not apply to the minimum 1-inch-thick “noncombustible material” required on mass timber floors.
Figure 3 Only combustible surfaces require protection in a Type IV-HT concealed space when Option 3 is used under IBC Section 602.4.4.3. Courtesy of ATF Fire Test Report (FPL GTR247): Figure 101.203924_825870.
3312.1 Fire safety requirements for buildings of Types IV-A, IV-B and IV-C construction. Buildings of Types IV-A, IV-B and IV-C construction designed to be greater than six stories above grade plane shall comply with the following requirements during construction unless otherwise approved by the fire code official: 1. No change to text… 2. No change to text… 3. Where building construction exceeds six stories above grade plane and noncombustible protection is required by Section 602.4 of the International Building Code, at least one layer of noncombustible protection shall be installed
on all building elements on floor levels, including mezzanines, more than four levels below active mass timber construction before additional floor levels can be erected. Exceptions: 1. Shafts and vertical exit enclosures shall not be considered part of the active mass timber construction. 2. Noncombustible material on the top of mass timber floor assemblies shall not be required before erecting additional floor levels. 4. No change to text…
Figure 4 Prior to mass timber construction extending above the 6th story, one layer of “noncombustible protection” must be applied to all mass timber surfaces, where such protection is required by IBC Section 602.4, on all floor levels more than four stories below active mass timber construction. Courtesy of 2021/2024 IFC Commentary. O CTO B ER 2023
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Justification
and 602.4.2.3), as it does not have any particular assigned protection time associated with it. IFC Section 3312.1, Item 3 requires that, prior to mass timber construction A layer of “noncombustible material” applied to the floor during construcextending above the 6th story, one layer of “noncombustible protection” must tion could be damaged during the continued construction process, with be applied to all mass timber surfaces, where such protection is required by equipment and materials moving across it. The potential for damage would IBC Section 602.4, on all floor levels more than four stories below active occur during the entire construction process and could result in the need for mass timber construction. The intent of this provision, which appears both repairs of the noncombustible material. For example, the weight of loaded in the 2021 IFC and the 2024 IFC, is to limit the amount of exposed wood drywall carts used later in construction to provide the required “noncomat any one time during the construction process (Figure 4). bustible protection” for walls and ceilings can cause damage to cast-in-place “Noncombustible protection” is a defined term in the I-codes and is associ- noncombustible materials typically used on mass timber floors. ated with a specifically assigned protection time. However, “noncombustible Per IFC Section 3312.1, there is no requirement for “noncombustible protection” is not the same thing as the minimum 1-inch-thick “noncombus- protection” to be installed over mass timber floors during construction. tible material” required on mass timber floors (per IBC Sections 602.4.1.3 Rather, Item 3 of IFC Section 3312.1 applies only to noncombustible protection. The addition of IFC Section 3312.1 Exception 2 is primarily meant to provide clarification that the requirement in IFC Section 3312.1, Item 3 does not apply to the minimum 1-inch-thick “noncombustible material” required on mass timber floors. While it doesn’t apply in either the 2021 IFC or the 2024 IFC, FOR REDUCED the latter now includes an exception to GLOBAL WARMING state this explicitly.
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Conclusion In the 2024 IBC and 2024 IFC, several changes were made to mass timber provisions, including the following: • The allowable unprotected mass timber area on the ceiling for Type IV-B construction is increased from 20 percent to 100 percent of the floor area in any dwelling unit or fire area • The minimum 15-foot separation distance between unprotected mass timber elements now only applies to the distance between unprotected areas on walls • Item 3 of IBC Section 602.4.4.3 was changed to clarify that protection only needs to be applied to combustible surfaces in Type IV-HT (heavy timber) concealed spaces • Clarification that construction sequencing requirements for the protection of mass timber elements during construction do not apply to the minimum 1-inch-thick “noncombustible material” required on mass timber floors Structural engineers responsible for mass timber design should be aware of these changes in the 2024 I-codes.■ John “Buddy” Showalter is a Senior Staff Engineer with the International Code Council (bshowalter@iccsafe.org)
by CTS Cement Manufacturing Corp .
CTScement.com 800.929.3030 28 STRUCTURE magazine
Jason Smart is the Director of Fire Engineering with the American Wood Council (jsmart@awc.org)
historic CODESSTRUCTURES and STANDARDS FAQ on SEI Standards What you always wanted to ask. By Jennifer Goupil, P. E., F. SEI, F. ASCE
T
his quarterly article addresses some of the questions received about structural standards developed by the Structural Engineering Institute (SEI) of the American Society of Civil Engineers (ASCE). In addition, questions from engineers, building officials, and other design professionals are often considered to develop future editions. Following are some questions received by SEI and responses to clarify the provisions.
Supplements Include Critical Revisions ASCE 7-22 was published in December of 2022, but I heard there is a supplement to update the referenced standards. Why is there a supplement, and where can I find it? The publication of a supplement is a formal process to provide additional consensus provisions to the edition of the standard already published. This frequently happens following the completion of a cycle to address coordination issues that were not possible to address during the standard development cycle. Another reason for a supplement is to update references that are not yet complete to a point where they can be incorporated at the time of publication. In the case of ASCE 7-22, the committee developed two supplements. The first one, Supplement #1, (March 21, 2023), includes several updates to referenced standards to bring in the most current editions. Additionally, a few coordination items were included in the supplement. The affected chapters include Chapter 6, Tsunami Loads and Effects, Chapter 14, Chapter 15, Chapter 23, Chapter 26, and Chapter 29; additionally, the provisions in the commentaries were updated in Chapters C6, C12, C13, C14, C15, C26, C29, and C30. The provisions in Supplement #2 (May 25, 2023) include a complete rewrite of Chapter 5, Flood Loads. This revision also includes flood load-related changes to Chapter 1 and Chapter 2. Supplements #1 and #2 were completed after the ASCE 7-22 adoption into the I-Codes. Therefore, both will be brought forward into the next code adoption cycle for the 2027 I-Codes. Both supplements can be found at asce.org/asce7.
Updates to Chapter 5 in ASCE 7 What is the scope of ASCE 7-22 Supplement #2? It only includes Chapter 5, Flood Loads, so how do I use it? The scope of the supplement includes the revisions and updates to Chapter 5, Flood Loads. As part of the update, Section 1.3.1.3 and Sections 2.2, 2.3.2, and 2.4.2 are also included for completeness. As published in Section 5.1 of Chapter 5, The provisions of this chapter apply to buildings and other structures located in a Flood Hazard Area. This chapter shall not apply to the design of levees, dikes, piers, wharves, roads, or bridges. As a supplement to the published 2022 edition, the document was published after the base document was adopted into the 2024 International Building Code (IBC), therefore the supplement will be proposed for adoption into the 2027 IBC. The supplement is published in the ASCE Library and available as a free download at asce.org/asce7.
Designing for the 500-year Floodplain How does the ASCE 7-22 Supplement #2 use the 500-year floodplain? How is this different from the 7-16 provisions? The Supplement uses a new design approach! The requirements of Section 5.3 tie flood hazard mitigation design to Risk Category, consistent with other environmental hazards in ASCE 7 and different from the 2016 provisions. Furthermore, the 500-year floodplain now defines the Flood Hazard Area and applies to all risk categories except for Risk Category I; see the language below. 5.3.1 Flood Hazard Area – For Risk Categories II, III, and IV structures, the Flood Hazard Area shall be the 500-year floodplain designated as the Special Flood Hazard Area and the Shaded X-Zone. For Risk Category I structures, the Flood Hazard Area shall be the 100-year floodplain designated as the Special Flood Hazard Area.
Relative Sea Level Change Does the ASCE 7-22 Supplement #2 require any impacts from relative sea level rise? Yes! It is clearly stated in Section 5.3.4. The effects of relative sea level change shall be included in calculating flood conditions and flood loads for sites whose flooding comes from coastal sources. The section also defines that the project lifecycle of not less than 50 years shall be used and that, at a minimum, the rate of relative sea level change shall be the historically recorded sea level change rate for the site over a 50-year period. This article’s information is provided for general informational purposes only and is not intended in any fashion to be a substitute for professional consultation. Information provided does not constitute a formal interpretation of the standard. Under no circumstances does ASCE/SEI, its affiliates, officers, directors, employees, or volunteers warrant the completeness, accuracy, or relevancy of any information or advice provided herein or its usefulness for any particular purpose. ASCE/SEI, its affiliates, officers, directors, employees, and volunteers expressly disclaim any and all responsibility for any liability, loss, or damage that you may cause or incur in reliance on any information or advice provided herein. If you have a question you want to be considered in a future issue, please send it to sei@asce.org with FAQ in the subject line. Visit asce.org/sei to learn more about ASCE/SEI Standards.■
Jennifer Goupil, P. E., F. SEI, F. ASCE, is the Managing Director of the Structural Engineering Institute and the Chief Resilience Officer for the American Society of Civil Engineers.
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Photo courtesy of Alex Francis, P. E., S.E.
The Future of Infrastructure Repair A closer look at the west seattle bridge rehabilitation project. By Clyde Ellis
F
or nearly 40 years, the West Seattle Bridge has been a primary route connecting West Seattle to the greater Seattle metropolitan area. The bridge spans 1,300 feet and is comprised of three cantilevered segmental box-girder concrete sections that rise to a maximum height of 140 feet over the Duwamish Waterway. In March 2020, the bridge was abruptly shut down to all traffic, disrupting the lives of those traveling to and from West Seattle for what would turn out to be nearly 2.5 years. The shutdown occurred because routine inspections had identified accelerated growth of cracks at a significant enough level that immediate stabilization was needed, followed by either long-term repairs or replacement of the bridge. In 2013, inspections revealed cracks forming in the webs and slabs of the bridge’s two main girders. A series of more frequent inspections was performed, which included some epoxy crack injection installation of crack monitoring technology. Between 2013 and 2019, increases in crack growth continued to cause concern. A new engineering analysis was performed, confirming exponential crack growth, which prompted SDOT to close the bridge to
30 STRUCTURE magazine
traffic in March 2020. After an extensive evaluation and planning period, a dedicated project team was formed to handle the emergency repair project for the bridge. A two-phase approach to stabilization and long-term repair was developed. Phase 1 focused on the stabilization to mitigate any concerns regarding potential collapse. Phase 2 would involve either replacement of the bridge or comprehensive long-term repairs and upgrades necessary to restore and extend the life of the existing bridge. Phase 1 of the bridge repairs, which began in late 2020, required the use of a customized access system consisting of scaffolding and working platforms, which streamlined work taking place underneath the structure hundreds of feet in the air. The phase 1 repair plan was essential to stabilize the structure, while a determination could be made about the future of the bridge structure. The scope of the phase 1 repairs was extensive and included three parts. First, epoxy injection of the cracks was necessary, which consists of filling the cracks with epoxy resin to restore structural integrity and prevent further damage.
Next, external post-tensioning was installed within the concrete girders. Post-tensioning is a technique for reinforcing concrete, enhancing its performance under both normal and adverse conditions. And third, carbon fiber reinforced polymer (CFRP) was installed on the concrete at select locations along the superstructure to pro- SDOT Phase 1 Stabilization. vide additional reinforcement. CFRP is a composite material known for its high strength-to-weight ratio, making it ideal for strengthening structures and enhancing their durability. These comprehensive measures were undertaken to ensure structural stability of the bridge while planning ensued for Phase 2. While the initial stabilization project (phase 1) was performed in 2020, comprehensive studies were completed to determine whether the best path forward was long-term repairs or replacement of the bridge. Based upon the studies completed, the owner, Seattle Department of Transportation, chose a phase 2 path of long-term repairs, which began in late 2021.
Innovative Construction Techniques Based on their extensive experience, as well as their completion of Phase 1 repair activities, PULLMAN was selected as a subcontractor for the Phase 2 construction and working in conjunction with STRUCTURAL TECHNOLOGIES and Simpson Strong-Tie provided expertise for implementation of: • Epoxy crack injection • CFRP (Carbon Fiber-Reinforced Polymer) wrapping • Quality control One of the first issues that needed to be addressed was the significant cracking that had taken place over time, which was made worse by increased traffic combined with the effects of seawater that had seeped into the cracks and corroded the embedded reinforcement. Epoxy crack injection is a highly effective method for filling and sealing cracks in concrete. Specifically formulated epoxy is injected into the cracks under pressure, ensuring a strong bond with the surrounding concrete and a watertight seal. Contractors worked closely with engineers to locate and document all cracks in six areas on the two bridge girders that had been identified as high risk. This process was scrutinized closely in the early stages of the project, including the validating penetration of the materials through core sampling. This invasive testing became less frequent as the project progressed and confidence in the process was established. By the completion of the project, over 15,000 linear feet of crack injection repairs had been made, equating to nearly three miles. This process not only extended the life of the bridge but enhanced its overall strength and stability, while -other repair scopes were being completed. CFRP, or carbon fiber- reinforced polymer, technology is an innovative technique that played a vital role in the success of the project. CFRP is a lightweight, high-strength composite material that offers exceptional corrosion resistance, making it an ideal choice for strengthening concrete structures in demanding environments. Both interior and SDOT Phase 2 Rehabilitation.
exterior CFRP strengthening was installed on the existing spans, increasing the concrete’s capacity to meet the demand from the design loads. In some cases, it was necessary to anchor the CFRP. To do this, Ground-Penetrating Radar (GPR), non-destructive testing equipment was first used to locate the embedded reinforcement within the concrete to ensure no rebar would be damaged while drilling holes into the concrete. A piece of carbon fiber was inserted into the hole and then splayed out onto the fabric already installed. A thin layer of epoxy was applied over the CFRP to ensure a strong, durable bond to the concrete. The combination of the CFRP and anchors allows the CFRP to reach a much higher strain under loading conditions having a greater impact on the concrete’s load-carrying capacity. There was a set of strict quality control guidelines associated with the CFRP installation process as well, including documentation of information such as surface preparation details, temperatures, and dew points. Proper quality control procedures for CFRP applications also include recording all lot numbers of materials utilized – epoxy, carbon fiber and all coatings used in the process. Finally, verification of the appropriate bond to substrate and tensile strength of the materials are important to ensure design requirements are met. The bond is tested using ASTM D4541 to demonstrate that the CFRP is adhered to the substrate at 200-psi or greater, which was required for this project. The tensile strength is verified using ASTM D3039 testing. The CFRP used in the field is sampled each shift, and the 12ʺ × 12ʺ sample panels are sent out for tensile testing at an approved laboratory.
Unique Jobsite Challenges Construction projects on or around bridges bring their own set of challenges, ranging from access to traffic control. The West Seattle Bridge also has unique challenges specifically related to its height. The bridge runs high atop a series of other roadways, bridges, waterways and alongside power transmission towers. The majority of the repairs completed were at 100-feet or more above the ground. Scaffolding was erected around the existing structure, and suspended platforms were put in place as a base of operation. There were areas where the erected and installed access could not reach
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Epoxy crack injection.
Access platforms.
along the underside of the bridge. For these areas, the team needed to utilize an Under-bridge Inspection Truck (UBIT). The UBIT is an articulating bucket at the end of an arm anchored to the platform, providing access to hard-to-reach areas. For all those working at height, whether on scaffolding or in the UBIT, proper training was provided, and safety harness protocols were in place throughout the project.
against materials and debris falling into the water. All necessary procedures were put in place to avoid these issues. One of the most unique aspects of the project was having to work around the activities of the Spokane Swing Bridge directly underneath. This bridge remained open during construction, serving as the main thoroughfare between West Seattle and nearby neighborhoods. However, the bridge would periodically need to open to allow boat traffic to pass through. The two spans would each rotate 45 degrees on a turntable rather than raising into the air like a drawbridge. Construction crew kept in contact with bridge personnel and generally had about 10 minutes’ warning each time the bridge was going to open. During this time, they would have to move box girders and any other materials that might be in the way, all from the floating platform hundreds of feet in the air. Overall, the unique aspects and tight timeline to complete the repairs made for a fast-paced project, enhancing the importance of safety training and performance.
Environmental Challenges Seattle is known for its damp and rainy weather conditions, and this created special challenges for the project team. The frequent rain and winds posed two types of challenges, including safety and operational. Safety of the workforce is the top priority, so when strong winds or other inclement weather that could be harmful occurs, job sites are shut down causing delays. The rain also causes a major operational concern when CFRP is being installed, as it could impact surface conditions, and a clean, dry surface is required. Special tents were erected around work areas to ensure that the environment remained dry. The areas under construction remained dry. Heaters and dehumidifiers were used to ensure the temperature and humidity remained consistent. Any significant fluctuation in these conditions could prevent the CFRP and epoxy from curing properly, and therefore compromise the integrity of the strengthening techniques. In addition, working over an active waterway made it necessary to guard
CFRP installation at girder.
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Results On September 15, 2022, after nine months of the phase 2 construction project, the West Seattle Bridge officially passed its final safety test. The last two suspended platforms were removed, and the bridge was reopened to public traffic on September 17th. Throughout the repair process, rigorous safety procedures and quality control measures were in place to ensure that the work was completed safely and met the highest performance standards. With the impact on the community the bridge closing caused, and the importance of re-opening, the use of CFRP to strengthen the West Seattle Bridge demonstrates the effectiveness of innovation and technology in addressing infrastructure challenges.■ Clyde Ellis serves as a Vice President for STRUCTURAL TECHNOLOGIES, leading the company’s structural strengthening business in the western region of North America. His focus is on retrofitting existing commercial, public, and transportation structures to meet new seismic codes, implementing structural changes for change of use, and resolving issues related to construction defects and design errors. Clyde specializes in working with clients to provide turnkey, design-build solutions for complex infrastructure projects. He brings 23 years of experience working throughout the United States and internationally. Clyde is a graduate of North Carolina A&T State University and Lehigh University with degrees in Architectural and Civil Engineering.
iconic STRUCTURES The Golden Gate Bridge
The most famous bridge in the world, a symbol of San Francisco and American ingenuity. By Roumen V. Mladjov, S. E., P. E.
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he Golden Gate Bridge is one of the world’s most famous and admired structures. Spanning the picturesque Golden Gate Strait north of San Francisco, the bridge transforms the strait into a more beautiful and dramatic setting. This unique site and its bridge are a graceful and majestic entry into the San Francisco Bay, a breathtaking sight welcoming vessels from all over the Pacific. Built between 1933 and 1937, the Golden Gate a) b) Bridge became a symbol of the City of San Francisco Golden Gate Bridge, San Francisco, 1937: a) Overall view, b) South Tower, a view from the bridge deck. and American ingenuity and progress. It is one of the greatest bridges ever built and certainly much simple and visually powerful structure that we admire today. the most celebrated of all. The suspension steel bridge structure is 6,450 The engineers relied on recent advances in Suspension Bridge Design ft (1,966 m) long (the entire bridge, approaches included, is 8,980 ft Theory for the design. They verified these calculations with tests on a (2,737 m) long). It carries six traffic lanes and two pedestrian/bicycle steel tower model of 1:56 scale (56 times smaller than one of the actual lanes. The height of the bridge towers is 746 ft (227 m); (152 m (500 towers). The tests confirmed that the tower calculations were sound. ft) above the deck); the navigation clearance is 220 ft (67 m). With a scaled-down force, one test simulated the actual 120 million The bridge links San Francisco with Marin County and the North pounds (54,000 metric tons) of vertical load that would be placed Bay at the points of the shortest distance across the Bay entrance. Long atop each full-sized tower by the main cables. (To visualize that much considered an impossible dream by Californians, together with the San weight, picture a large ocean liner.) Francisco-Oakland Bay Bridge, the Golden Gate Bridge made the Bay The geology of the south tower location was investigated before conArea into a unified economic entity, significantly contributing to its struction began. This tower was planned for construction over 1,100 future development as a major financial and cultural center. The site feet (335 meters) offshore on serpentine rock. Consulting geologist, provides the essential background for a great bridge. Andrew Lawson, oversaw a load test performed by placing weight The Golden Gate Bridge was designed by Joseph Strauss (Chief equivalent to a fully loaded railroad boxcar on an area of serpentine Engineer) and his task group of extraordinarily experienced design and rock only 20 inches (508 millimeters) square. The rock was more than consulting engineers: Charles Ellis, Leon Moisseiff, Othmar Ammann, strong enough. and Charles Derleth Jr., together with the geologist Andrew C. Lawson. The bridge’s central span held the long-span world record until Working closely with the engineers, architect Irving Morrow was 1964 when the Verrazano Narrows Bridge surpassed it by 18 meters. responsible for the aesthetic design, including the signature Art Deco Invariably on the list of the greatest bridge structures, the Golden style of the bridge towers and the bridge’s characteristic “International Gate Bridge is also included in ASCE’s list of Modern Wonders of the Orange” color. World. What makes this structure so unique and famous? Far from In 1921, Strauss submitted an initial design for a bridge that would being “merely” utilitarian, the Golden Gate Bridge is one of the few cross the Golden Gate Strait — a hybrid bridge with a suspension span structures significantly enhancing its environment. Combining the supported by cantilever trusses extending from the bridge towers. The breathtaking setting and the elegant, powerful structure contributes idea was considered “ugly” by the contemporary local press. However, to its appreciation as one of the greatest bridges ever built. The everStrauss’ design was ahead of its time. His idea was to significantly reduce changing conditions, from bright sunlight and shades to drifting fog the suspension span (preserving the longer clear span), something often obscuring bridge elements, offer spectacular visual variations. employed much later for “hybrid suspension” bridge structures with Pedestrian accessibility on the bridge deck and at multiple viewpoints considerable savings vis-à-vis classic suspensions. along the structure makes it a favorite site for photographers and tourWith the engineering team’s help, the bridge’s design evolved into the ists, adding to its popularity. The elegant lines of the suspension cable
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system, its long span, and the majestic towers create a familiar and fascinating picture. This structure, perfect in both functionality and design, is also an object of art. The bridge is a monument to the creative spirit and the eternal drive to surpass previous achievements. To fully appreciate this achievement, one must consider the project’s challenges and the state of design and construction in the 1930s. The strait is a 6,700 ft (2,042 m) wide opening in a mountain range, where the Bay connects to the Pacific Ocean, with its strong tides and currents, winds exceeding 60 mph, and grade up to 330 ft (100 m) below the water surface. These conditions required an enormous bridge span never achieved before. As Kevin Starr The early hybrid bridge design option submitted by Strauss in 1921. rightly noted, “Not since the Brooklyn Bridge was built more than half a century earlier had bridge-builders The earthquake caused 68 deaths, at least 3,700 injuries, and an estifaced such a challenge.” mated loss of $6-7 billion. Although the Golden Gate Bridge suffered We should also remember that in the 1930s, there were no computers, no observed damage from the Loma Prieta Earthquake, since the episoftware, or even electronic calculators. The engineers had to rely on center was located some 60 miles to the south, the earthquake served hand calculations and slide rules alone. There were no mobile cranes, as a reminder of the area’s susceptibility to seismic activity and initiated welding, or high-strength bolts; all connections had to be done with an extensive seismic retrofit program. rivets – a particularly challenging method, considering the difficult - In 1996, three more retrofitting projects commenced. The first atmospheric conditions over open waves. Despite such challenges, two—on the Marin (north) approach viaduct and the San Francisco the engineers and builders accomplished the task, building a bold and (south) approach viaduct—are already completed (1997–2008), so efficient bridge concept. On more than one occasion, accidents delayed the construction. A few months after construction began in 1933, a ship traveling westward in thick fog crashed into the just-completed access trestle to the San Francisco tower fender and destroyed a large part of it; later the same year, strong storms twice destroyed part of the access trestle. These accidents delayed progress on the bridge by five months. Despite all obstacles, the structure was completed ahead of schedule in less than 4 ½ years for $33.7 million, $1.3 million below budget! The cost is equivalent to $710 million in 2023. However, in 2019 it was estimated that building the same bridge today would cost about $1,640 million. The Golden Gate Bridge is a high-level engineering achievement with a new record-long span at a very challenging site, a structure many experts had considered impossible to build. The main span’s 4,200 ft (1,280 m) length exceeds the spans of two bridges connecting Europe and Asia at the Bosphorus Strait (with respective 3580 ft (1,090 m) and 3524 ft (1,074 m) spans). The 66,043-metric-ton steel structure (including anchorages) requires periodic inspections and permanent maintenance to ensure its safe operation. During its long years of service, the bridge has been retrofitted several times: - In 1953–1954, a lateral bracing system was added between the stiffening trusses to increase the lateral and torsional resistance of the bridge. - In 1973–1976, all suspender cables were replaced. - In 1982–1986, the original reinforced concrete deck was replaced with a stronger and lighter steel orthotropic deck, a replacement done in stages during night hours without closing traffic. Orthotropic deck consists of a structural steel plate stiffened with ribs. - In 1980–1982, the North and South approach structures were seismically reinforced. On October 17, 1989, the Loma Prieta Earthquake hit the San A scale model of one of the Bridge towers, loaded in a civil engineering testing Francisco Bay Area with a 7.1 magnitude, with 15 seconds duration. machine at Princeton University in 1933. O CTO B ER 2023
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Description, Technical, and Statistical Data
Elevation of Golden Gate Bridge.
the Bridge is expected to safely withstand an earthquake over 7.0 in magnitude. However, it may still experience damage in major seismic events that would require traffic closures. The final retrofit Phases 3A and 3B will further strengthen the Bridge against earthquakes or other disasters by reinforcing the main and side spans of the Bridge, both towers and the south tower pier, with work scheduled to start in late 2024 and finish in 2029. These efforts reflect natural concerns over seismic safety in the area. In the mid-1990s, the U.S. Geological Survey (USGS) estimated a 62% probability of at least one magnitude 6.7 or greater earthquake capable of causing widespread damage, impacting the San Francisco Bay region before 2031. More recently, USGS estimated a 72% probability of a magnitude 6.7 or greater earthquake in the Bay Area before 2043. Because of the significant strength of the steel-wire main cables, the load-carrying capacity of the structure does not need reinforcement and remains as originally designed. One unexpected load test occurred in 1987 when too many people assembled on the bridge deck during the 50th-anniversary celebration of the bridge. The celebration attracted 750,000 to 1,000,000 visitors, and the crowd on the bridge was about 300,000 people, causing the bridge’s center span to flatten out under the weight. This unexpected load caused the main structure to deflect, consuming all designed camber of the main span and temporarily transforming it into a concave line. The pedestrian “crowd” load exceeded by 50% the bridge design live load of 7.25 t/m’ (6 traffic + 2 pedestrian lanes). This super load caused a larger-than-designed deflection, but the structure successfully resisted the overload; the required tensile strength for the two main cables is 224,000 kips (101,900 metric tons) (for the total load above), while the capacity is 262,000 kips (119,000 metric tons), i.e., there was still a safety factor of 1.17 vs. factored load and 2.44 safety factor vs. nominal load demand.
The bridge under construction.
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The main bridge has a typical suspension bridge structure with two majestic towers and an elegant, simple suspension cable shape on one central-main span and two side spans over a continuous steel stiffener girder. The stiffener girder comprises two steel trusses, laterally braced in between, carrying the bridge deck. Originally the deck was reinforced concrete, replaced in 1982-1986 by a steel orthotropic deck system. The towers are 227 m tall from the water level or 152 m above the deck. They are steel-framed two-leg structures with art-decoenhanced horizontal frame connections. Between both legs, each tower has four horizontal frame connections above the deck and two “X” braces below the deck. - The length of the central main span of the bridge is 4,200 ft (1,280 m); the two side spans are 1,125 ft (343 m) each, with a total suspension length of 6,450 ft (1,966 m). The bridge length is 8,980 ft (2,737 m) between abutments. - Width of the bridge deck: 90 ft; road width between curbs: 62 ft. - Vertical clearance above water level: 220 ft (67 m). - Main cables length: 7,650 ft (2,332 m); main cable maximum sag: 144 m; cable diameters: 36ʺ 3/8 (0.92 m) with the wrapping. Each main cable has 27,572 galvanized steel wires with a diameter of 0.192ʺ. - Main cables weight: 24,500 t (22,200 m. tons). - Strength characteristics of the cable steel wire: tensile strength, Fu = 235,600 psi; yield strength, 182,600 psi. - There are 250 pairs of suspenders arranged 50 ft (15.2 m) apart, each with a diameter of 2 11/16ʺ. The original suspenders were replaced in 1972–1976. - Weight of all cables, main and suspender, and accessories: 24,500 tons (22,200 metric tons). - Total weight of each anchorage: 60,000 tons (54,400 metric tons). - Total weight of the bridge, excluding anchorages and approaches: 419,800 tons (380,800 metric tons). This includes a reduction of 12,300 tons (11,158 metric tons) in weight from the re-decking in 1986. - Maximum calculated deflections at midspan: downward, 10.8 ft (3.3. m); upward, 5.8 ft (1.8 m); transverse deflection: 27.7 ft (8.4 m). - Deflections at the top of towers: transverse, 12.5 in (0.32 m); longitudinal, 22 in (0.56 m). - Live load capacity: 4,000 lbs. (1,814.4 kg) per lineal foot. - Load on each tower from main cables: 61,500 tons (56,000 metric tons). Bethlehem Steel manufactured the steel structures in Trenton (New Jersey), Sparrows Point (Maryland), Bethlehem, Pottstown, and Steelton (Pennsylvania). They were transported by sea through the Panama Canal to the construction site in San Francisco. The cables for the bridge were produced and supplied by John A. Roebling’s Sons Company in Trenton, New Jersey. Humankind has built bridges since the days of early civilizations. Several of them reflect the eternal aspiration to surpass previous achievements in construction. Some, like the Golden Gate Bridge, are landmarks that became symbols of cities, countries, and human progress. The American Society of Civil
The Golden Gate Bridge under construction.
Engineers rightly recognizes the bridge as one of the Wonders of the Modern World. To this day, the Golden Gate Bridge remains a symbol of San Francisco. It is what the Eiffel Tower is for Paris and what the Statue of Liberty is for New York. Admiring this iconic structure, we should honor its designers and builders, engineers,
construction companies and workers, those who have updated and retrofitted it, and those who maintain it daily. This amazing structure inspires and motivates new generations of engineers and builders to higher structural and bridge engineering achievements. The Golden Gate Bridge has inspired generations of engineers to build larger, taller, and stronger structures. It symbolized the Art of American Bridge engineering and contributed to the leading role of American bridge designers and builders for most of the 20th century. This 86-year-old achievement should also motivate our engineers, builders, and relevant authorities to deliver more high-performing and efficient bridge structures to maintain our country’s transportation functionality and safety at the highest level.■ Full references are included in the online version of the article at STRUCTUREmag.org.
Roumen Mladjov, S. E., P. E., Roumen’s main interests are structural and bridge development, structural performance, seismic resistance, efficiency, and economy. (rmladjov@gmail.com). The Golden Gate Bridge. O CTO B ER 2023
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When the Ground Shook Post-disaster observations of the kahramanmaraş turkiye earthquake sequence — Part 2 By Reid Zimmerman, Egemen Sšnmez, and Rebecca Collins
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his is the second of a two-part series on the Kahramanmaraş Earthquake Sequence which occurred on February 6, 2023 in Turkiye. The first article was printed in the STRUCTURE magazine July 2023 issue and presented a background on regional seismicity, seismic design and practice in Turkiye, and the authors’ observations from the field. This article focuses on observations relevant to structural practice in the U.S.
Relevance of the Kahramanmaraş Earthquake Sequence to the United States Given the spatial separation and cultural differences between Turkiye and the United States, it is easy to fall into the mental trap of preemptively concluding that the damage and casualties seen in the Kahramanmaraş Earthquake Sequence are not representative of what may occur in the United States. And while it is true that differences in design, materials, construction, inspection, and enforcement do exist, it is important to consider that: • The building stock in the U.S., similar to Turkiye, is a mix of older and newer buildings in proportions that reflect time periods of growth for different cities. For example, nonductile concrete buildings constructed before the 1980s in western U.S. cities exhibit at least as poor detailing and strength characteristics as those of more modern reinforced concrete buildings in Turkiye, many of the latter of which were severely damaged or collapsed. • Even for new Risk Category II buildings in the U.S., a 10% probability of collapse given the Risk-Targeted Maximum Considered Earthquake (MCER) is all that is assured in ASCE 7. While many engineers have and continue to argue that this is a conservative estimate of collapse for what actual designs produce, it is still a pressing reminder that the building code in the U.S. targets reducing the probability of collapse, not eliminating it. For a brief overview of collapse targets in ASCE 7, please see “Acceptable Collapse?” in the March 2015 issue of STRUCTURE magazine (https:// www.structuremag.org/?p=8164). 38 STRUCTURE magazine
• Seismic shaking intensities over the geographic and population extent subjected to the Kahramanmaraş Earthquake Sequence in Turkiye have never been experienced in the U.S. to date. Notably, the shaking intensities experienced in the Kahramanmaraş Earthquake Sequence exceeded the average values computed by ground motion prediction equations, the same or similar ground motion prediction equations which are used to derive seismic hazard demands in U.S. building codes. With a better understanding of the devastating effects of the Kahramanmaraş Earthquake Sequence, structural engineers in the U.S. may begin to question the futility of attempting to change the outcome of a similar earthquake in the U.S. However, the authors encourage U.S. practitioners to instead be reminded of structural engineers’ essential role and the immensely meaningful impact we can make. The following sections discuss observations from the Kahramanmaraş Earthquake Sequence which are especially relevant to U.S. practice.
Structural Observation and Special Inspection are High-Value Structural observation and special inspection are extremely highvalue tasks, meaning they produce large benefits to building performance for relatively lower levels of effort/time. Structural observation and special inspection are often code-required in the U.S., particularly in the higher seismic regions of the western states. This requirement is sometimes seen as a burden by structural engineers to make time for a site visit in an already too-busy schedule. Due to contracting practice in Turkiye, it is very uncommon that the structural engineer who prepares the contract documents also has the opportunity to observe or inspect their design during construction. Even for significant structures, the authors are aware of instances in Turkiye where the structural engineer who prepared the drawings had their first opportunity to visit the building only after the earthquake. In Turkiye, a separate field engineer is hired who often has no prior relationship to the design. The authors observed multiple buildings for which construction differed from the prescribed design (e.g., missing or inappropriately spaced rebar stirrups and ties in reinforced concrete columns, conduit or duct interrupting structural elements, etc.) (Figure 1). These seemingly small details, which the design engineer understands fundamentally and would recognize immediately if on site, can have major detrimental impacts to building performance. Therefore, the authors encourage U.S. practitioners to remember that structural observation and special inspection are much more an opportunity to enhance public safety than a burden on their time.
Figure 1 Duct through shear wall concentrating shear failure at unplanned opening.
regulation in 2013 requiring that all new hospitals with a bed capacity greater than 100 be constructed using seismic isolation. Of the approximately 100 seismically isolated buildings in Turkiye, eleven seismically isolated hospitals were within the affected region of the Kahramanmaraş Earthquake Sequence (Figure 2). All performed very well, particularly in comparison to the significant structural damage or collapse exhibited by fixed-base buildings. Although the first seismically isolated hospital in the U.S. (University of Southern California University Hospital which opened in 1992, also the first known modern seismically isolated hospital in the world) was constructed almost a decade prior to the first in Turkiye (Kocaeli University Hospital in 2001), Turkiye has now far surpassed the U.S. in the total hospital floor area protected by seismic isolation as a result of the Ministry of Health regulation. Some of the reasons for the stagnation of seismically isolated buildings in the U.S. are described in “What’s Happened to Seismic Isolation of Buildings in the U.S.?” in the March 2012 issue of STRUCTURE magazine (https://www.structuremag.org/?p=4166). While the performance of seismically isolated buildings in Turkiye was not perfect, owing primarily to issues with structural observation and inspection of moat clearance, the Kahramanmaraş Earthquake Sequence may be
Seismic Isolation Works Seismic (base) isolation works and, if not the only appropriate solution, it is at least by far the best option for certain occupancies such as acute-care hospitals in a high seismic region. The Ministry of Health for Turkiye released a
Figure 2 Seismically isolated hospitals in the earthquake-affected region. Reproduced from “The Response of Seismically-Isolated Hospitals in the Kahramanmaras Earthquakes of February 6, 2023”, Report by the Turkish Association for Seismic Isolation, May 10, 2023.
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In the U.S., seismic retrofit occurs somewhat infrequently, typically either as a result of voluntary efforts by concerned owners or as mandated by jurisdictional rules or building codes. For example, the International Existing Building Code (IEBC) requires seismic evaluation and retrofit for a change of Risk Category or a significant alteration. Under the IEBC, alterations only trigger an evaluation and retrofit if more than a certain percentage of the gravity members are affected or if the lateral force-resisting system is significantly altered. Furthermore, certain local jurisdictions impose mandatory seismic retrofit when overall renovation costs per square foot exceed a certain limit. Such alterations are uncommon or, alternatively, the alteration is modified to avoid triggering an evaluation and retrofit. Additionally, multiple jurisdictions in the western U.S. have enacted ordinances for the seismic evaluation and retrofit of certain existing building types (e.g., unreinforced masonry, wood soft-story, non-ductile concrete, Figure 3 Weak/soft story collapse of the first story in an apartment building in Nurdaǧı, etc.). See Figure 3 for a weak/soft story collapse in Turkiye. Gaziantep. Such mandates appear to be appropriately targeting the most a wake-up call for increased seismic isolation of acute-care facilities seismically vulnerable existing buildings and yet the percentage in high seismic regions of the U.S. of retrofitted existing buildings in the high seismic regions of the U.S. remains low. Furthermore, similar to Turkiye, seismic evaluation and retrofit mandates in the U.S. are susceptible to public and political Seismic Retrofitting Occurs Slowly pressures (e.g., competing demands with the housing crisis). Seismic retrofitting of existing buildings in the U.S., in combination with demolition and rebuilding, is a necessary component of improving life-safety on a community level. The Turkish government enacted a tax following the 1999 Duzce and Golcuk earthquakes which was intended to fund seismic safety improvements. However, those funds did not appear to primarily be used for seismic retrofitting of existing buildings but were rather diverted to new infrastructure and large public works projects. An urban transformation law was also enacted with the aim of encouraging owners to retrofit or demolish and rebuild their older buildings through financial support. However, this funding did not appear to motivate a large percentage of existing building owners. As a result, the authors did not observe any seismically retrofitted buildings in the earthquake-affected zone of Turkiye.
Functional Recovery for Existing Buildings May Detract from Life Safety A growing focus in the U.S. is the shift to functional recovery design or, in other words, design for enhanced performance beyond life safety/collapse considerations and towards reducing building downtime. This practice is generally looked upon favorably as it could better align future U.S. codes with the public’s performance expectations for buildings. Furthermore, in new building design, some version of enhanced functional recovery can often be delivered through reasonable incremental construction costs. See Figure 4 for a tunnel-form building visited by the authors with negligible recovery time which was in a region of otherwise severely damaged buildings. Refer to Part 1 of this article published in the July 2023 issue for a description of tunnel-form construction. The idea of design for functional recovery is also beginning to be considered for existing buildings in the U.S. with the understanding that incremental construction costs are likely not as favorable as for new buildings. While this is commendable, if the Kahramanmaras Earthquake Sequence is any indication of even just older building performance in a similar earthquake in the U.S., it is clear that a safety-based performance objective still requires significant attention for existing buildings. This conclusion, therefore, begs the question as to whether functional recovery design for existing buildings in the U.S. is appropriate, especially when the larger incremental construction costs for functional recovery retrofit of existing buildings could instead be allocated to improving safety-based objectives (i.e., life safety seismic retrofit).
Reduced Drift Limits Can Help Compensate for Other Factors Figure 4. Tunnel-form apartment building with negligible damage and downtime in Karacasu, Kahramanmaras.
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Similar to U.S. building codes, the 2007 Turkish Building Earthquake Code permitted typical buildings to displace to as much as 2%
story drift ratio in a design-basis earthquake. While both Turkish and U.S. engineers have the knowledge and capability to design structural systems to be stable and safe at those displacements, this quickly becomes complicated by errors in design or construction and nonstructural material availability and practices. For example, in multiple damaged buildings observed by the authors in Turkiye, column rebar dowels from the foundations were misplaced during construction and were bent over slightly to fit within the column core (Figure 5). This led to premature buckling and fracture of those bars (i.e., lesser ductility capacity than anticipated) in many instances and may have contributed to partial or total building collapse. As another example, nonstructural walls in Turkiye are almost exclusively constructed of unreinforced masonry due to material availability and labor knowledge. When these masonry walls are in-filled within a reinforced concrete frame, they are readily damaged at low levels of drift demand and also influence the response of the reinforced concrete frame (e.g., asymmetrical masonry damage in plan causing torsion, greater masonry damage at the lower stories causing weak/soft story formation, etc.). While both errors in design/construction as well as brittle nonstructural components can be addressed through other means (e.g., enhanced inspection and detailing, respectively), they can also be addressed by reducing allowable drift limits. For example, low-rise tunnel-form construction in Turkiye was observed to perform well (Figure 4) with high shear wall densities resulting in low drifts. Limiting drift, therefore, serves as a straightforward way of compensating for a milieu of other factors which would otherwise require interventions at multiple points in the design and construction process.
Post-Earthquake Inspection and Tagging Requires Communication
Figure 5 Misplaced vertical dowels in foundation bent over during construction to fit within correct column location.
Furthermore, while a rapid ATC-20 evaluation may only take tens of minutes, helping residents understand that evaluation and overcome the fear of entering a building that is even only cosmetically damaged is likely to take far longer.
Earthquakes Consist of Multiple Events Similar to the 2010-2011 Canterbury Earthquake Sequence in New Zealand where multiple high-intensity earthquakes occurred in series, the Kahramanmaraş Earthquake Sequence in Turkiye illustrated how earthquakes one after another can increase damage to buildings and loss of life. For certain buildings/sites, the Kahramanmaraş Earthquake Sequence produced near design-basis earthquake shaking compared to the Turkish Building Earthquake Code in the first event followed by
The authors regularly encountered residents in the earthquake-affected region of Turkiye who were unaware of the official safety and access evaluation for their building. Following the Kahramanmaraş Earthquake Sequence, an extensive evaluation process occurred to designate buildings as either Collapsed, Needs to be Demolished, Heavily Damaged, Slightly Damaged, or Undamaged using a rapid assessment involving a few minutes of observation by academics or government engineers (Figure 6). Despite this process, few to no physical tags were present and it was unclear whether residents were informed that the assessments were available online. In the U.S., post-earthquake tagging typically follows ATC-20 Procedures for Postearthquake Safety Evaluation of Buildings which involves placarding as Unsafe, Restricted Use, or Inspected after a rapid and, if necessary, a later detailed assessment. Yet, similar to cities in Turkiye, jurisdictions in the U.S. are likely to be ill-prepared to respond quickly to an event of similar intensity and extent to the Kahramanmaraş Earthquake Figure 6 Online map showing evaluation designation for buildings in Antakya, Hatay (data shown for late February Sequence due to lack of trained staff or 2023). Note that map above is not the same tool as residents use to look up designation on Turkish Ministry of lack of quick access to as-built drawings. Environment, Urbanization and Climate Change website. Courtesy of https://hasar.6subatdepremi.org/.
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Figure 7 Comparison of recorded spectra from the first and second event in the Kahramanmaras Earthquake Sequence (Mw 7.8 and Mw 7.5, respectively) versus the 2018 Turkiye Building Earthquake Code design-basis earthquake (DBE) for a site in Caglayancerit, Kahramanmaras.
significant, although not equal, shaking in the second event (Figure 7). As occurred in the Kahramanmaraş Earthquake Sequence, triggering of adjacent faults is also possible in the U.S. (e.g., multiple ruptures on the San Andreas Fault System). The authors visited a collapsed building in the city of Kahramanmaraş which had sustained damage but allowed everyone to evacuate during the first event (Figure 8). Several residents had re-entered to search the building and collect belongings when the second major earthquake occurred nine hours later. The building collapsed killing all those still inside. In the U.S., similar to Turkiye, the building code does not consider an explicit performance objective for multiple earthquakes in series. While the implied ability of a building to sustain aftershocks is often made, the quantity and intensity of those aftershocks and the explicit capacity of a damaged building to resist them are not quantified. This leads to questions about whether a building that survived a design-basis earthquake shaking and then collapsed in a high-intensity aftershock would meet the performance expectations of the U.S. building code. If aftershock resistance is expected of code-conforming buildings, explicit consideration and checks would need to be introduced into ASCE 7.
Figure 9 Temporary cell phone tower and generator in Antakya, Hatay.
Adaptation is Necessary In a post-earthquake environment like that following the Kahramanmaraş Earthquake Sequence, adaptation plays a necessary part in recovery. Whether that be in the form of (a) university students switching to fully remote learning, (b) hospital staff moving more critical departments to the ground floor due to a lack of elevator function, or (c) temporary installation of cell phone towers (Figure 9), finding alternative ways to get things done was a reality of the situation in the earthquake-affected region of Turkiye. That is not to distract from all the ways in which response and recovery following the Kahramanmaraş Earthquake Sequence could have been improved (of which there are many). Rather, it speaks to what the U.S. will have to expect following a major earthquake.
Conclusion It is easy to fall into the mental trap of concluding that the damage and loss of life seen in the Kahramanmaraş Earthquake Sequence of February 6, 2023 are not representative of what may occur in the United States. However, the lack of a significant earthquake in the U.S. on the scale of the Kahramanmaraş Earthquake Sequence combined with much of the same underlying code philosophy between the U.S. and Turkiye may suggest otherwise. Rather than be discouraged by the observations from the Kahramanmaraş Earthquake Sequence, the authors hope that U.S. practitioners will see the opportunity to take the lessons learned from Turkiye and apply them here at home.■
Acknowledgments are included in the online version of the article at STRUCTUREmag.org. Reid Zimmerman, P. E., S. E. (reid.zimmerman@kpff.com) is the Technical Director at KPFF in Portland, OR and has focused his career on design, evaluation and retrofit of buildings in regions of high seismicity. Egemen Sönmez, Ph.D. (egemen.sonmez@ieu.edu.tr) is an Assistant Professor at Civil Engineering Department of Izmir University of Economics, Turkiye. His research interests include but not limited to seismic design, assessment, and numerical modeling of reinforced concrete structures.
Figure 8 Building in Dogukent, Kahramanmaras which survived the first event but collapsed in the second earthquake (collapsed building in foreground of photo).
42 STRUCTURE magazine
Rebecca Hix Collins, P. E., S. E. (RebeccaC@cplinc.com) is a Senior Structural Project Manager at Coughlin Porter Lundeen in Seattle, WA with extensive experience in structural renovations spanning many material types.
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structural OBSERVATIONS Observations of the Bridge Damage Caused by the Mw 7.8 Turkey (Türkiye) Earthquake of February 6, 2023. By Prof. Robert K. Dowell, Ph. D., P. E.
A
Mw 7.8 earthquake, followed nine hours later by a Mw 7.5 earthquake, struck southern Turkey (Türkiye) on February 6, 2023, leaving tens of thousands of residential buildings, as well as mosques, churches, industrial buildings and silos, collapsed and damaged beyond repair. Bridge structures were severely damaged but did not collapse, with the exception of a simply supported, single-span bridge that fell off its supports at the abutments, with no reported injuries. This provides a stark contrast to the buildings, where the overwhelming majority, if not all, of the more than 50,000 deaths occurred. And this is the official death toll based on the number of bodies that were pulled from the rubble of the collapsed buildings; considering that over 300,000 individual apartments were destroyed, with perhaps several people living in each, the number of people killed in these two back-to-back earthquakes could be many times higher than the official count. Bridge structures are designed to allow significant damage from a major seismic event, but without collapsing, as should also be the case for buildings. On the older Richter Scale, this 7.8 moment magnitude of the first earthquake translates to about a M 8.1 event, which is of similar size and fault type (right, strike-slip) to the famous 1906 San Francisco earthquake (M 8.2 on the Richter Scale and back-calculated to Mw 7.9 per the United States Geological Survey (USGS). Even the time of day (local time) was similar between the California and Türkiye earthquakes; the 1906 San Francisco earthquake occurred at 5:12 am while the first 2023 Türkiye earthquake happened at 4:17 am, less than an hour apart, and in both cases when most people were still at home, sleeping. The fault rupture length of 180 miles from the Mw
7.8 earthquake in southern Türkiye is equivalent to the distance in California between San Diego and Santa Barbara, with the City of Los Angeles right in the middle. The structural engineering reconnaissance team (Mountain Goats) included Gulen Ozkula (team leader), Robert K. Dowell (author of this article), Tunc Deniz Uludag, Ayse Hortacsu and Jui-Liang Lin. While the Mountain Goats inspected many different types of structures, the focus of this article is on observed bridge damage. Two significant bridges had severe and unusual damage, the Nurdagi Viaduct and Asi Bridge.
Earthquake Details Epicenters and fault ruptures of back-to-back Mw 7.8 and Mw 7.5 earthquakes The epicenter of the Mw 7.8 earthquake was between Nurdagi and Gaziantep at GPS coordinates N 37.225° E 37.021°, while the epicenter of the Mw 7.5 earthquake that happened nine hours later was at GPS coordinates N 38.024° E 37.203°, north of Kahramanmaras and Golbasi. Fault rupture lengths for the Mw 7.8 and Mw 7.5 earthquakes were 180 miles and 99 miles, respectively. The second earthquake is not an aftershock to the first event because it occurred on a different fault, but it was probably triggered by the sudden shaking of the larger Mw 7.8 earthquake, which affected strains and stresses throughout the complex fault system in the region. The maximum horizontal slip from
Author at the observed fault rupture of Mw 7.8 2023 Türkiye earthquake (left) and fault rupture from this event continuing through open fields into the distance.
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USGS-defined fault rupture line for the Mw 7.8 earthquake showing epicenter, locations of the Nurdagi Viaduct (Bridge 1) and Asi Bridge (Bridge 2), as well as observed fault rupture by the author – and map of ground shaking intensity from the Mw 7.8 earthquake (USGS).
the first event was 30 feet, compared to 20 feet from the 1906 San Francisco earthquake. However, energy release from these two events was similar because the fault rupture length in the famous California earthquake was longer than in Türkiye. For such a large earthquake, the normal (shortest) distance from a structure to the fault rupture line is much more important than the distance between a structure and the epicenter, as the ground shaking intensity contours given above clearly demonstrate.
0.581 g, respectively. In the vertical direction, PGAs were 0.354 g for the Nurdagi Viaduct and 0.589 g at the Asi Bridge. Peak measured horizontal accelerations at the two bridges of 0.607 g and 0.659 g are close to the maximum horizontal acceleration of 0.7 g in California bridge design for a Mw 8 event.
Earthquake Spectra
For the Nurdagi Viaduct, the measured ground motions (from Station 2712, the closest strong motion station at 2.00 miles from the bridge) in the EW and NS horizontal directions have Peak Ground Accelerations (PGAs) of 0.607 g and 0.565 g, respectively. Likewise, for the Asi Bridge, the measured ground motions (from Station 3124, the closest strong motion station at 2.14 miles away from the bridge) in the EW and NS horizontal directions have PGAs of 0.659 g and
For the Nurdagi Viaduct, the acceleration response spectrum (ARS) plot in the EW direction tends to be larger than the smoothed Caltrans design ARS curve for a Mw 8 earthquake that has a PGA of 0.7 g on rock or stiff soil, and follows a similar trend with increasing structural period, while the NS direction ARS curve is often below the Caltrans design ARS curve. Maximum spectral acceleration values at this bridge are 1.83 g and 1.90 g in the EW and NS horizontal directions, respectively, which are both larger than the peak Caltrans ARS design value of 1.82 g. The EW spectral displacement curve follows a similar trend to the design curve up to a period of about two seconds, then
Nurdagi Viaduct, horizontal NS direction (strong motion Station 2712, Mw 7.8 earthquake).
Nurdagi Viaduct, horizontal EW direction (strong motion Station 2712, Mw 7.8 earthquake).
Asi Bridge, horizontal NS direction (strong motion Station 3124, Mw 7.8 earthquake).
Asi Bridge, horizontal EW direction (strong motion Station 3124, Mw 7.8 earthquake).
Measured ground motions
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Nurdagi Viaduct, horizontal spectra (5% damped), NS and EW directions (strong motion Station 2712, Mw 7.8 earthquake), and smoothed Caltrans bridge design spectra for M8 earthquake with a PGA of 0.7 g on rock or stiff soil.
Asi Bridge, horizontal spectra (5% damped), NS and EW directions (strong motion Station 3124, Mw 7.8 earthquake) and smoothed Caltrans bridge design spectra for M8 earthquake with a PGA of 0.7 g on rock or stiff soil.
drops below it. In the NS direction, the spectral displacement curve is typically lower than the design curve, matching it only at a period of one second and, again, at four seconds with over two feet of relative displacement. In the vertical direction, the maximum spectral acceleration value was 1.37 g. The ARS plots for the Asi Bridge also show a higher peak value in the EW direction than from the smoothed Caltrans ARS design curve, but at a significantly longer natural period. Maximum ARS values for the Asi Bridge are 2.15 g and 1.44 g in the EW and NS horizontal directions, respectively, compared to the peak value of 1.82 g from the design curve. Thus, while the maximum acceleration in the EW direction is larger than the peak design value, the largest result in the NS direction is lower than this. A shift to the right for the maximum values of the ARS curves, compared to the design ARS curve, which is based on rock or stiff soil, is a clear indication that soft soil is present at the site of the Asi Bridge, which was later confirmed. Both EW and NS horizontal directions show this shift of the ARS curve to longer periods compared to the smooth design curve. The peak spectral displacement in the NS direction is close to 5 ft at this soft soil site. The Caltrans ARS curve was obtained from an earlier version of the Seismic Design Criteria (SDC), since the current version of the SDC does not have such a graph readily available. The maximum spectral acceleration in the vertical direction was 1.64 g. 46 STRUCTURE magazine
Two Significant Bridges with Severe and Unusual Damage Nurdagi Viaduct The Nurdagi Viaduct is a large structure in the low mountains of southern Türkiye with cantilever reinforced concrete (RC) columns that have a diameter of 10 feet and a height of about 80 feet. GPS coordinates for this structure are N 37.170960 E 36.699940 and an elevation of 2563 feet. The bridge includes two side-by-side structures with five spans each that are curved and consist of a superstructure combination of precast, prestressed concrete girders and steel girders, with steel used for the longest span. While this viaduct is 18.1 miles from the epicenter of the Mw 7.8 earthquake, it was less than one-tenth of a mile from the fault rupture line; the strongest intensity shaking for an earthquake of this magnitude runs along the region of the fault rupture line, not in concentric circles about the epicenter, as clearly shown in the figure above. An unexpected plastic hinge formed part-way up one of the large RC cantilever columns, which is unusual since the maximum
Different views of the Nurdagi Viaduct, including a column plastic hinge part-way up one of the RC columns, as well as precast concrete and steel superstructure spans.
Various views of the column plastic hinge that formed part-way up one of the 10-ft diameter RC columns of the Nurdagi Viaduct.
bending moment is expected at the column base where it interfaces with the fixed footing. The observed damage shows that the plastic hinge formed in the transverse bent direction. Concrete spalled off on both sides of the column, and vertical rebar buckled on one side of the column, with yielded and significantly deformed transverse rebar, as clearly shown in the figures above. For both cases, large moments are required in both transverse bent loading directions. Recent meetings in Ankara, Türkiye, between the author and the bridge engineer who is doing the seismic retrofit design of this viaduct confirmed that there were various bar cutoffs up the column height, which could explain why the plastic hinge formed part-way up the column and not at its base. There was also damage to the abutments, which is expected from such a significant earthquake.
Asi Bridge over the Asi River The Asi Bridge consists of two side-by-side, six-span bridges of precast, prestressed girders and a RC topping slab with Asphalt Concrete (AC) overlay for the driving surface of the superstructure. GPS coordinates for this bridge are N 36.255050 E 36.204300 and elevation of 315 feet. The columns and footings are cast-in-place
RC. At the time of the inspections the bridge was still being used by vehicular traffic. Recent meetings between the author and the bridge designer confirmed that it is no longer used by vehicular traffic, and it will be replaced with a new bridge. The Asi Bridge was 80.8 miles from the epicenter of the Mw 7.8 earthquake, but only 2.5 miles from the fault rupture line, with the damage and measured intensity of shaking clearly showing the significance of the distance to the fault rupture line rather than to the epicenter of a large earthquake, as discussed previously. Unusual and severe damage occurred at the ends of the simplysupported precast girders, with cracking and spalling of web concrete over long distances from the support at the abutments. This occurred on both interior and exterior girders. With vertical spectral accelerations of above 1.6 g, as given above, the girder ends lifted off their supports, one side and then the other, often losing the rubber bearing pads that had supported them. Thus, the girder ends were impacting in the vertical direction, concrete-to-concrete, as well as in the longitudinal and transverse directions, resulting in severe multi-directional cracking and spalling. This forced the prestressing strands to slip forward to maintain a transfer length, which further exasperated the stresses and spalling. Also, vertical web rebar buckling occurred, pushing the concrete out in both O CTO B ER 2023
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Asi Bridge crossing the Asi River.
External shear key damage and failure for Asi Bridge.
Extensive end-of-girder damage at Asi Bridge.
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Buckling of vertical web reinforcement and buckling of the full web at precast girder ends, as well as failure of external and internal shear keys at the abutment of the Asi Bridge.
directions, increasing the length of spalling and damage. In some cases, there was no web concrete remaining, with only the rebar cage toward the girder ends supporting the shear loads at the abutments. Prestressing was lost, including whole strands coming out of the girder. In addition, lateral loading caused exterior and interior shear keys to fail, while longitudinal loading resulted in column plastic hinges at their base, as expected. Significant settlement occurred at both approaches to the bridge.
Summary The Mw 7.8 earthquake and the Mw 7.5 earthquake that occurred nine hours later, both on February 6, 2023, caused extensive damage to southern Türkiye, with tens of thousands of buildings collapsing, resulting in more than 50,000 people killed and leaving millions without homes. Industrial facilities, silos, churches, and mosques also collapsed. Of particular interest is that while bridges were heavily damaged, only one collapsed; a simply supported, single-span bridge that slipped off its supports at the abutments, with no injuries reported. There is an important distinction here; buildings are privately funded and operated, with little or no
oversight to their design and construction, whereas bridges are state-owned, designed and built to a higher engineering standard. This good record of bridges in Türkiye demonstrates that it is possible to design and build high-quality structures to withstand a major earthquake without collapse. Buildings had low concrete strength and poor rebar detailing and were often not built to current seismic specifications, resulting in the extreme number of buildings that collapsed. Measured ground shaking intensity maps and observed bridge damage levels showed that the normal (closest) distance from a structure to the fault rupture line was much more important than the distance to the epicenter of the earthquake for a large seismic event.■ Full references and additional images are included in the online version of the article at STRUCTUREmag.org. Prof. Robert K. Dowell, Ph.D., P. E., is Associate Professor of Structural Engineering and Director of the Structural Engineering Laboratory at San Diego State University (SDSU). He has over 30 years experience of bridge design, structural analysis and physical testing to failure in the laboratory. He can be reached at (rdowell@sdsu.edu).
Settlement at both approaches of Asi Bridge.
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structural EFFICIENCY Accelerated Bridge Construction (ABC) Benefits
How ABC can be applied to concrete construction to save time, money and improve safety. By Ahmed Clayiff, P. E.
A
ging and deteriorating infrastructure is an ongoing safety issue in our communities. It has been a challenge for many owners to address the problems and meet the traffic demands of the public. Existing structures are required to be inspected every two years, and conditions are rated per the National Bridge Inspection Standards (NBIS) by comparing the existing condition to its new condition. The rating system is as follows: 7-9 is good, 5-6 is fair, and 0-4 is poor. Structures with severe deterioration are either posted with a lower load capacity or are permanently closed and are categorized as structurally deficient (SD). Bridges are also checked for issues related to the functionality of the existing structure. When the geometry doesn’t meet the current traffic demand or the current design standards, the structure is called Functional Obsolete (FO). Based on the statistical data shown in Figure 1, in 2020, there were 45,031 bridges, or about 7.3% of the structures included, classified in poor condition. This substantial quantity requiring replacement or rehabilitation presents many challenges, specifically for structures needing replacement in areas with high Average Daily Traffic (ADT).
Figure 1 US Bridges Rated in Poor Condition, Bureau of Transportation Statistics.
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In this case, Accelerated Bridge Construction (ABC) methods can help with a reduction in onsite construction time of about 90% and improves safety. This article will compare the traditional concrete construction method of cast-in-place to the alternative precast ABC method. Methods are compared based on schedule, safety, traffic challenges, environmental impact, cost, and quality. An essential consideration for the design and construction of ABC products is also included.
Traditional Bridge Construction Challenges Traditional bridge construction methods include a cast-in-place concrete substructure and a partial or complete superstructure. This method requires all construction activities to be done on-site, including form installations, material storage (i.e., reinforcement), concrete mix delivery, and pouring concrete. These activities present several challenges when replacing existing structures related to schedule, safety, traffic challenges, environmental impact, cost, and quality.
Challenges & Solutions With all those traditional bridge construction challenges, there is a need to utilize an improved process and innovative system to address the need for aging infrastructure and improve safety. The ABC method is an innovative construction technique that consists Figure 2 FHWA Work Zone Fatality Facts and Statistics, FHWA, Office of Operations. of prefabricating bridge elements offsite and transporting them to the site for installation. Due to its benefits, ABC construction on a portion of the bridge or by installing a temhas gained immense popularity in the bridge construction industry porary bridge adjacent to the existing bridge. Even the best of in recent years. these solutions negatively impacts daily traffic with increases in delays, congestion, and accidents, which increase with the construction duration. The additional traffic also affects local Schedule businesses, activities, and schools. Traditional Construction - The construction duration for a typical traditionally constructed bridge can range from a few months to a few years on larger projects. The schedule is subject to various variables, including material availability, unexpected weather, and contractor staffing, all of which can cause substantial delays. Longer duration projects leave themselves open to an increased risk of safety and labor concerns. ABC Construction - Bridge elements are fabricated in a controlled environment. This mitigates the weather impact and helps create a realistic and predictable schedule. Pieces are then shipped to the site erected in place and connected. This process reduces the construction sequence by eliminating the need for forms on-site and the curing duration. This also offers a reduction in construction equipment quantity and mobility. The most significant reduction can be seen in closure duration, which can be as minimal as a weekend for ABC versus two to three months for traditional construction.
ABC Construction - The project schedule is shorter, which leads to a substantial reduction in traffic impact.
Environmental impact Traditional Construction - Traditional construction methods face several environmental challenges, including material waste, wastewater generation, water contamination, noise, and air pollution. Construction equipment utilization is on-site longer, and a larger workspace is needed, resulting in an increase in land disturbance. If over a waterway, disturbances to navigation or biological species, including the possibility of endangered species, and construction time restrictions also impact the job.
ABC Construction - The project schedule is shorter, which reduces pollution and possible land and water passage disturbance.
Safety
Cost
Highway construction zones are highly hazardous to the traffic and construction personnel on-site. According to the federal highway (Figure 2), fatalities are increasing annually. The duration of construction directly impacts safety; longer construction duration leads to higher exposure to potential accidents. Several factors are attributed to this issue are the construction staging process, traffic pattern changes, narrow roads, limited mobility space for construction equipment, and traffic congestion.
Traditional Construction - While the construction cost of the bridge may be reasonably predicted, there are several less obvious costs that can be impacted by the construction method. Traffic can have economic impact on motorists taking detours and waiting for traffic delays to clear. Traffic delays impact commuters, neighboring businesses, and deliveries. Safety incidents cause delays and lead to short- to long-term staff losses, thus impairing product quality.
ABC Construction - The project schedule is shorter, which increases safety by limiting the exposure of the construction personnel in the construction zone and the possibility of motorist accidents.
ABC Construction - Several factors discussed earlier can lead to substantial cost savings during the construction and service life of the structure. Another potential cost benefit is that future deteriorated or damaged pieces can be replaced with less effort. However, there are costs associated with the delivery and connection of ABC elements that are not seen in traditional construction. The cost should be finalized during the design process by ensuring the proposed structure is a good candidate for ABC bridge construction.
Traffic Challenges Traditional Construction - Traditionally, phased construction is used for high ADT structures. Traffic flow is maintained during
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Quality Traditional Construction - Cast-in-place construction relies on timely and quality delivery of the concrete mix. Weather delays can significantly impact the overall schedule by delaying concrete pouring, affecting concrete mix quality, and impairing the curing process. All of this can lead to poor concrete quality with the possibility of repair needed and deterioration during its service life. ABC Construction - The quality is higher because all elements are constructed in a controlled environment without the risk associated with concrete mix delivery. This improves the piece’s finishing and the structure’s service life, requiring less maintenance. The quality of the structure depends on the design and handling processes, which require careful consideration.
ABC Bridge Design and Construction Concerns Depending on the structure size, the bridge likely consists of multiple pieces shipped to the site, erected, and connected together. Ensuring that all benefits are achieved will require an effective design methodology, a high-quality control process, and careful consideration of means and methods. These design and construction concerns are divided into technical and practical categories.
Technical • Camber is an essential design factor in prestressed superstructure elements in Girders and deck panels. During the design process, it should be carefully calculated and designed to avoid potential large differential that will lead to issues during construction and service life. Those issues include excessive grouting and alignment, which may cause potential deficiencies such as cracking. • Post-tensioning is utilized to connect bridge decks and lock them together. The design drawings should include detailed post-tensioning, properties, sequences, and procedures. • Deck joints located at the maximum negative moment area are subject to cracking; therefore, they should be carefully considered and designed. • Repetition is critical to gaining manufacturing efficiencies that offer cost savings in materials, time, and labor. The design of the piece’s geometry, reinforcement, shipping hardware, and connections should be considered. • Concrete strength should be carefully selected by considering the process of handling pieces for stripping, storage, and erection. A possible effective solution for closure pours is utilizing an alternative concrete product known as Ultra-High Performance Concrete (UHPC), which can achieve a strength of 18,000 psi and higher. • Several connection types could be utilized, including. ˏ Grouted splice couplers that connect precast elements are used primarily in substructure connections. Selecting the proper coupler with adequate tolerance is crucial because it will allow for field adjustments without needing modification. Coordinating with the coupler supplier is an effective way to avoid misinterpretations of utilization and design challenges. ˏ Mechanical threaded couplers are mainly utilized for deck panel connections. 54 STRUCTURE magazine
ˏ Grout material specification and strength should be carefully considered and specified for each application. • Shear pockets in the deck connect the bridge deck panels with the girders; this provides the composite action between the two members. Ensuring adequate reinforcing length, concrete covers, and grout strength are crucial to mitigating potential cracks and deterioration. • Drawings must be thoroughly reviewed during design to avoid misalignments requiring field modifications. The drawings and specifications should include allowable tolerances for all design elements, hardware, and connection details.
Practical • Finding local precast manufacturers/contractors with the capability and efficiency to produce and construct the proposed structure. Those include skills, equipment, and transportation. • Careful consideration of the site conditions to ensure crane mobility and operational space. This includes overhead utility lines, nearby railroads, and site closures/detours. • Prefabricated elements for roadway transition, including approach and sleeper slabs, should be completed during the same time frame as the bridge elements. • Local restrictions and permitting requirements for shipping and handling include pieces’ weight and geometry to avoid possible oversized loading. A possible solution for the heavy-weight pieces, specifically the substructures, is to fabricate them with voids (i.e., utilize corrugated metal pipe). ˏ The void can be filled with concrete on-site and utilized as a connection. ˏ Another solution is to use lightweight concrete, which offers a weight reduction of nearly 20% or more.
Quality control • Ensuring all connections are properly installed and connected. • Ensuring elements are fabricated and constructed within allowable construction tolerance.
Conclusion Several challenges exist in providing our communities and industries with an up-to-date infrastructure system that prioritizes improving safety. Projects that are ideal candidates for ABC technology can offer several benefits over traditional construction methods. Those benefits include reduced construction duration, lessened environmental impact, lower cost minimized traffic impact, and improved quality.■ Full references are included in the online version of the article at STRUCTUREmag.org.
Ahmed Clayiff, P. E., CBSI, owns Clayiff Engineering, LLC. He has experience in various structural engineering areas. Mr. Clayiff is also an adjunct faculty and has taught various engineering courses. He can be reached at (aclayiff@clayiff.com).
structural COLLABORATION Efficient Steel Bridge Design & Construction Using Collaborative Fabrication Models
WSP is using OpenBrIM to model steel girder bridges with improved efficiency and accuracy. By Douglas J. Dunrud P. E.
B
lueprints, like cassette tapes and Blockbuster Video are now relics of the past. The transportation infrastructure industry must undergo a similar paradigm shift to make use Building Information Models (BIM) that have the potential to make bridge design more accurate, fast and dynamic.The Federal Highway Administration (FHWA) is leading an effort entitled BIM for Infrastructure that enables users to exchange data from one discipline to the next, indicating who is building what, when each part will be built, the materials to be used, and how it will be constructed. Typical transportation infrastructure projects use roadway design software such as Bentley OpenRoads Designer or Autodesk Civil 3D for creating the roadway geometry. Recently, WSP began using the software platform OpenBrIM for the digital deliver these bridges with a dynamic link to the roadway geometrics. This model-centric workflow using OpenBrIM will provide dramatic improvements in both efficiency and consistency in delivering the traditional deliverables of plans and quantities, but this is only the beginning of the advantages of the 3D bridge models. This article is focused on the potential advantages of using collaborative design and fabrication models in lieu of the traditional workflow process, as shown in Figure 1.
https://www.fhwa.dot.gov/construction/bim/pdfs/integrated_digital_project_delivery_fhwa_hif_20_021.pdf The traditional shop drawing workflow involves two independent data sets for design and fabrication with coordination between the two sets relying on 2D shop drawings. This process is rooted in mid-20th-century technology when paper drawings were the necessary tool for communication. The collaborative model-centric work-flow is not new, and it has a proven track record, and WSP has groups that are using it with great success. However, there are significant differences in both the nature of the contracts and the type of structures as compared to the traditional infrastructure projects. Both the challenges and the potential advantages of using collaborative design and fabrication models for the anticipated curved steel bridges are discussed below.
LOD 400 Fabrication Models The in-model review process is not new or untested, and two case studies will be presented. Both of these models are considered Level of Development (LOD) 400 models as defined by the American Institute
Traditional Shop Drawing Workflow
Contract Plans
Fabricator's 3D Model
Shop Drawings
Engineer's Comments
Shop Drawings
Engineer's Approval
Collaborative Model-Centric Workflow In-model reviews Design 3D Model
Fabricator's 3D Model
Figure 1 Traditional vs collaborative shop drawing workflow.
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Engineer's Approval
of Architects (AIA). “An LOD 400 element is modeled at sufficient detail and accuracy for fabrication of the represented component. The quantity, size, shape, location, and orientation of the element as designed can be measured directly from the model without referring to non-modeled information such as notes or dimension callouts.” https://bimforum.org/resource/ level-of-development-specification/ Both of the case study models were developed using Tekla Structures. The success of the LOD 400 modeling is hard to deny. The model provided numerous benefits such as — improved collaboration, enhanced visualization, and error reduction. • A. 66 Hudson Yard WSP Hagerstown developed the fully connected Tekla model for the owner on the 66 Hudson Yard project (Figure 2). Also known as the Spiral, this landmark project presented many challenges due to the unique geometry around the perimeter of the building and the thin interior core walls. Through the modeling, WSP worked directly with the designers and connection engineers to provide solutions for complex nodes, sloping columns, and unique truss layouts. As the project developed and a fabricator was chosen, our office customized and modeled connections to the fabricator’s preferences to speed up produc- Figure 2 Model and photo simulation of 66 Hudson Yard. tion and the approval process. With Trimble Connect – markups, to-dos, 2D drawing review, clash The 66 Hudson Yard model was also used for production control during sets, and other coordination were done using color representation for fabrication, and the Numerical Control (NC1) files exported from the an overall visual effect. The steps in the coordination process included: model were used to run the CNC equipment. This provided tremendous 1. Cloud mark-ups in the model value in both efficiency and quality. 2. To-Do Lists with assignees and status columns • B. Chenab Bridge in India 3. 2D drawing review similar to the traditional style A Tekla Structures model was also used for the Chenab Bridge as 4. Clash sets, which identify conflicts that are much better resolved in part of a new railway line between Udhampur, Jammu and Baramulla, the design phase Kashmir in northern India (Figure 3). Fabrication drawings of all the structures were extracted directly from the model. Whenever the model changed, the drawings changed as well. The bridge BIM models were a great advantage on site as well. The site crew was able to get additional manufacturing information from the models. Additional details on the use of the models for this project can be found in the e-brim article. BIM-forBridges-May-2023.pdf (e-brim.com) We are seeking to gain similar advantages for typical curved steel bridges by modeling them in OpenBrIM. The questions that arise in comparing the 66 Hudson Yard project and the Chenab Bridge to the land bridges are: 1. )Can models created in the design phase deliver similar advantages to models created for construction and fabrication? 2. )Does this process apply to typical highway bridges, or is it only justified on Figure 3 Tekla model of the Chenab Bridge. complex projects? O CTO B ER 2023
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the design profile. This is critical for fabrication since bolted connections require tight tolerances for “fit-up” at specific loadings and associated deflections.
B. Fabrication Adjustments Made to Design Data The fabrication models for steel plate girders also need to include adjustments for fabrication that are not typically included in design models. These include: 1.Welded Plate Girder Web Camber, which requires added flange length for the milling caused by the weld shrinkage. 2. Bearing Stiffeners Milled to Bear with added stiffener length to be milled to fit between the flanges. 3. Weld Joint Details, which involve chamfering plates to accommodate the welding process.
C. Multiple Models Based on Designed Fit Conditions
Figure 4 Stupp Bridge example.
Bridge Fabrication models In order to evaluate the applicability of collaborative design and fabrication models, we need to examine the additional factors that steel bridge fabricators considered in their models, which designers may not traditionally include. These adjustments are honed by years of experience and are often unique to particular fabrication shops.
A. Vertical and Horizontal (Camber and Sweep) Geometry The IBR project has many curved ramps with curved horizontal alignments along with parabolic vertical profiles. These girders also need to be cambered so that the final configuration with a dead load matches
Figure 5 Final vs. cambered model position.
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Steel bridges have multiple deflections, as shown in Figure 6, where two stages are shown superimposed to highlight the difference. • Red steel is the Total Dead Load representation (Final Position) • Green steel is the Steel Dead Load (SDL) Fit (Cambered) representation
Figure 5a gives a view of a girder splice. You can see the splice plates are only modeled in the cambered position (green); this way they show up on our girder drawings. Notice that there is some overlap of the bolts on the stiffener as well. Figure 5b shows a head on view of the girders and crossframes. It’s visible from the picture that the crossframes have been detailed in SDL fit condition and do not line up with the cambered stiffeners. This is a good view to note the extra holes (bolts) that had to be added to the stiffeners on the cambered girders. We need to model these so that the holes come in correctly on drawings and bolt lists. It may seem like finding Shangri-La to get design models capable of including the needed parameters to account for the additional needs of
Figure 6 Openbrim data-centric & parametric bridge workflow.
fabrication models. In the next section, we will discuss the capabilities of OpenBrIM and how realistic it is to account for these details.
report (see Figure 7). The analytical model can be exported to various software packages, including LARSA, Csi Bridge, Midas, STADD Pro, and OpenSees, among others, for additional analysis as well.
OpenBrIM Data-Centric and Parametric Bridge Workflow
B. Code Check
OpenBrIM is web-based software that you can access in a web browser. It includes 3D modeling, Finite Element Analysis (FEA), AAHTO Code Check, CAD and Quantities, Load Rating, Inspection and Health Monitoring (see Figure 6).
The engineer of record on bridge projects has the responsibility to ensure that all the applicable code requirements are met. In OpenBrIM, the national design code with any state amendments are library components that are easy to modify. The Summary Report is dynamic and is always updated based on the model properties (see Figure 8).
A. 3D Modeling and FEA The 3D Detailing Model and the FEA Analytical Model must have distinct characteristics. In a traditional bridge workflow, the analytical model and the 2D CAD details are in separate data repositories and require two sets of data input, introducing the potential for inconsistencies. OpenBrIM effectively shares data between the two 3D models and eliminates the possibility of inconsistencies between the models. The FEA includes moving loads based on influence surfaces and transfers the vehicle loads to the substructure for complete bridge design in one summary
Figure 7 Finite element analysis. O CTO B ER 2023
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Figure 8 Summary report of code check.
C. Parametric 2D Drawings and Quantities Perhaps the most valuable use of the OpenBrIM model is the automated production of 2D Plans. Although OpenBrIM does not include CAD capability, it can dynamically link 2D drawings to reference sheets in MicroStation. This way, all the clients’ MicroStation CAD requirements can be met including using the full capabilities of MicroStation, such as “named boundaries” and intelligent sheet borders. OpenBrIM is also being used for dynamic quantity reporting including a full embodied carbon analysis. These quantities will be exported to various databases with additional attributes, such as design notes and specifications.
D. Fabrication Models The above features more than justify the use of OpenBrIM, but creating an exchangeable model for fabrication has the potential to change the industry. It has been said that the design and fabrication models must be distinct; however, the value proposition makes it worth continuing our pursuit. None of the needed model features in the fabrication model are beyond the capabilities of OpenBrIM. However, we are not getting the full support of the fabricators that are involved in the National Steel Bridge Alliance (NSBA). There are three possibilities we see for why this is the case: 1. There are fabrication model needs that are beyond the abilities of OpenBrIM that we have not yet learned. 2. The industry is committed to the use of the Industry Foundation Class (IFC) format that is being developed by Building Smart. 3. The fabricators get paid to create the fabrication models, and they don’t want to give that up. This is understandable, as they have invested years to develop these bridge modeling capabilities. Despite the obstacles, we are committed to developing these fabrication models in OpenBrIM since we are required to deliver models that should meet LOD 400 standards and reflect the fabricators processes. 60 STRUCTURE magazine
Conclusion There are clearly challenges in developing collaborative design and fabrication models for curved steel girder bridges, including the unique processes that fabricators have developed over the years and their trade secrets. We are hoping that the continued “openness” that we experienced in recent workshops and that seems to be a characteristic of our industry will prevail and those who share the most will be rewarded the most. Building Smart has been endeavoring for years to identify everything that is needed for the IFC bridge format. The philosophy of this project is essentially the exact opposite. We are using OpenBrIM to parametrically model a curved steel girder bridge and make as many iterations as necessary to converge on a solution that is exchangeable based on feedback from fabricators. OpenBrIM has demonstrated the ability to make the adjustments to the model geometry quickly when they know what is needed. Obviously, the amount of feedback we have received from fabricators is a small sample size compared to the large number of processes that exist. It may be naïve to believe that we can account for all the potential combinations, but through persistence, it is achievable, and that the return on investment will add value to our industry for years to come. The National Steel Bridge Alliance is the key organization to facilitate modeling all the different fabrication processes. OpenBrIM can develop a “suite” of parameters that can be turned on or off depending on the specific fabricators who will ultimately be involved in the project. It would help if there was a convergence of fabrication practices in the coming years to arrive at a more-or-less standardized fabrication practice. We recommend that a fabricator representative be included in the design team to facilitate integrated project delivery. Whether our objective is achievable, difficult, or impossible seems to depend not so much on the task itself but rather on who is making the evaluation.■ Doug Dunrud, P. E., is Vice President and Technical Principle at WSP in Sacramento. He has been active in the development of Building Information Modeling (BIM) for bridges for the last 20 years. (Douglas.Dunrud@wsp.com)
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structural DESIGN Building Enclosure Design to Accommodate Wood Shrinkage
Recognize how and where building enclosures must accommodate differential shrinkage in wood-framed buildings. By Tammy J. Siliznoff, M. S., P. E. (CA)
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imensional change in wood, often called wood shrinkage, is an important consideration for wood-frame multi-story buildings. The decrease in moisture content (MC) of wood from constructionstage to in-service conditions can be over 10%, resulting in wood shrinkage at a rate of approximately 0.25% change in dimension per 1% moisture change. Wood shrinkage must be accommodated where there is differential movement between the wood structure and building components, such as cladding, fenestrations, MEP equipment, or interfaces with masonry structures. Cladding elements not accommodating wood shrinkage can experience cracking, spalling, buckling, or reverse slope issues.
Background The magnitude of dimensional change in wood varies depending on the grain orientation, wood species, and change in MC. Since wood is an anisotropic material with different properties in tangential, radial, and longitudinal directions, knowing the grain orientation of the wood is essential. Wood shrinkage is most significant in the tangential and radial directions while usually negligible (less than 0.2% [Rowell 2005] in the longitudinal direction, as shown in Figure 1). Therefore, a designer should assume tangential orientation as a conservative approach when calculating wood shrinkage unless more specific information is available. Thus, most shrinkage in wood-frame buildings occurs at floor lines where rim joists and sill plates are installed with tangential and radial grain directions aligned with the height of the building. Wood is also a hygroscopic material, readily absorbing moisture from the air or bulk water, which causes the wood to expand. When the moisture exposure decreases, the wood dries out and shrinks until the MC has reached equilibrium with the surrounding conditions. This cycle will continue for wood exposed to changing temperatures and relative humidity. For enclosed structures, the MC of wood framing is typically greater during construction when exposed to exterior conditions. When the building is closedin, the MC decreases until it reaches relatively consistent indoor conditions, resulting in a final equilibrium state with minimal dimensional change. The 2021 International Building Code specifies that preservative-treated wood shall not be enclosed when the framing members exceed 19% MC to minimize the risk of biological growth and, at the same time, limit the amount of wood shrinkage by limiting the MC differential between construction and in-service framing. Wood framing may have an MC above 19% due to wet storage conditions, from wetting during transit to rain events. A building’s structural design can greatly reduce the use of 62 STRUCTURE magazine
Figure 1 Typical shrinkage values at varying MC of wood in different grain orientations. Image courtesy of Building Enclosure Design Guide, Second Edition, BC Housing Research Centre.
members that may contribute to wood shrinkage, such as by using balloon-framed walls rather than platform walls or engineered lumber. However, some wood shrinkage is expected for light-frame and mass timber construction.
Mass timber Mass timber, such as cross-laminated timber (CLT) panels and glulam beams, have similar dimensional stability as dimensional lumber concerning changes in MC. However, it is likely to experience less shrinkage. This is due to the lower initial MC of the wood, which must be below 15% for the laminating process and is typically around 12%. Kiln-dried dimensional lumber is targeted to an average MC of 15%, at most 19%. The lower MC of mass timber is closer to the equilibrium MC of wood in interior spaces, which typically averages around 6 - 12% [Simpson 1999]. In addition, mass timber is less susceptible to MC increases and related dimensional changes from isolated, short-term wetting events due to the thicknesses of the members. The relationship between MC and the depth of wood is exponential from the outer plies to the inner core of mass timber. For example, in a recent six-story mass timber project, the wood shrinkage across the 5- to 7-ply CLT floors was determined to be 3/16-inch over a combined total of
Cladding Across PlatformFramed Floor Lines
Figure 2 Building enclosure includes continuity of air and vapor (red), water (blue is the water-shedding surface, and green is the water-resistive barrier), and thermal control layers between conditioned and unconditioned spaces.
Cladding across mass timber or traditional platform-framed floor lines is subject to wood shrinkage. It’s typical to have a gap in the sheathing at these locations for sheathing expansion during construction, which must translate through the air/water barrier and cladding. Figure 3 shows a wood-framed building with metal cladding spanning across platform wood-framed floors, which caused buckling of the cladding at floor lines. Through-wall flashing is the preferred detail to accommodate wood shrinkage at floor lines, as shown in Figure 3. This approach allows for wood shrinkage. It also provides through-wall drainage at each floor line to prevent water accumulation behind cladding over several stories, which can cause issues, particularly with cement plaster systems. Other options include overlaps or gaps in cladding and utilizing a UV-stable air/water barrier at gaps.
Differential Shrinkage of Cladding Differential shrinkage occurs when you have two materials that are interfacing but do not exhibit similar behavior when subjected to different moisture or temperature conditions, such as masonry cladding over a wood-frame building. The woodframe assembly typically experiences shrinkage after the building is closed as the wood dries, while the masonry often does not shrink. Clay masonry Figure 3 Platform-framed wood structure with metal cladding at window wall (left). The metal cladding is buckled is the most problematic because it expands when at the floor lines. Through-wall flashing accommodates dimensional change and provides drainage at each floor it absorbs air or bulk water moisture. Therefore, line. Images courtesy of Building Enclosure Design Guide, Second Edition, BC Housing Research Centre. it can compound the wood shrinkage disparity. Other materials, such as concrete masonry unit approximately 51 inches of CLT depth with a 10% MC difference (CMU)/mortar and concrete, do not expand when exposed to moisture and between the construction and closed-in conditions (measured in experience shrinkage due to drying and other mechanisms after pouring. the outer plies). Compare this to the expected wood shrinkage in When flashings and interfaces do not accommodate this displacement dimensional lumber, which is calculated to be approximately 2 between the materials, it can result in cladding cracking, spalling, buckinches in a similar building with platform-framed construction ling, or reverse slope on flashings. Figure 4 shows a 3-story, wood-frame with dimensional lumber. building with brick and stucco cladding. The brick is bearing on the reinforced Building Enclosure Design Goals concrete foundation, and the stucco is attached to the The building enclosure is what separates conditioned spaces from uncon- wood framing above the ditioned or exterior spaces. It consists of the air, water, vapor, and thermal brick. Wood shrinkage and control layers and relies on the continuity of these layers to keep the building clay brick expansion led to warm and dry (Figure 2). Part of an effective enclosure design allows move- back-sloped flashing. Other ment of the structure while maintaining continuity across these control layers. details on this project where Several common building conditions exist where wood shrinkage can wood shrinkage led to deficause failures in the building enclosure, including: ciencies include window sill • Cladding across platform-framed floor lines flashings and where brick • Cladding with expansive properties wall cladding interfaced • Concrete or masonry interfaces, such as zero-lot line interfaces or with soffit conditions. Figure 4 Three-story brick and stucco woodconcrete core Allowing for wood shrink- frame building. Flashing is back-sloped due to • Externally supported balconies age at cladding interfaces differential movement. O CTO B ER 2023
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can be accomplished with a properly sized sealant joint or overlapping metal flashing (Figure 5). The flashing overlap or sealant joints' size may differ for each floor based on the anticipated magnitude of wood shrinkage. The sealant joints for this project ranged from 1/2-inch wide on the first floor to 1-1/4-inch wide on the 4th floor, approximately three times the anticipated movement.
Concrete and Masonry Interfaces Differential movement is not limited to cladding materials. While CMU and concrete don’t expand like clay brick masonry, the shrinkage of masonry does not match that of wood. Therefore, this must be considered for areas such as elevator core walls, fire walls, and zero-lot-line walls. A similar approach that may include lapped flashing or sealant joints can be used in these areas. At parapet or rooftop interfaces, shrinkage of the entire structure below must be considered at the air barrier, water barrier, and water-shedding surface (metal flashing). This is accomplished by providing bellows in the air-barrier membrane, flexible water barrier sheet membrane, and lapped metal flashing as the water-shedding surface (Figure 6). At zero-lot-line wall interfaces where new wood-framed buildings interface with existing structures, including masonry, steel, or closed-in wood-frame buildings, movement can be accommodated with flexible joint material, such as silicone sheet or with metal flashing with sliding joints (Figure 7).
Figure 7 Plan of a zero-lot-line interface of a wood-framed building adjacent to a CMU wall of an adjacent building. A sliding metal joint allows the wood-framed wall to move independently.
Figure 5 Overlapped metal flashing to accommodate wood shrinkage and clay brick expansion.
Externally Supported Balconies Balconies that are externally supported must match the shrinkage characteristics of the building or increase the initial slope of the walking surface to avoid backslope, as shown in Figure 8. Other options for avoiding this condition include using bolt-on balconies, matching the balcony construction with that of the building, increasing the initial slope of the building to account for differential shrinkage, or using cantilevered balconies that are independently attached on each floor. 64 STRUCTURE magazine
Figure 8 Backslope of balconies can be caused by differential shrinkage of supports and buildings.
From a building enclosure perspective, bolt-on balconies are ideal since this approach simplifies detailing, eliminates saddle conditions, and reduces tie-in interfaces where detailing deficiencies are common. It also increases building performance by allowing air, water, and thermal barrier continuity at the wall-to-balcony interface.
Conclusion Accommodating wood shrinkage in the building enclosure starts with identifying interfaces where wood shrinkage will cause movement using strategies discussed, such as including properly sized sealant joints, lapped metal flashing, bellows in the air and water barrier membranes, using elastic membranes or providing additional slope in flashings or balconies. ■
Figure 6 CMU and wood-framed construction interface detailed to allow movement at the fire wall—pre-cured flexible silicone transition strip sealed to the foil-faced membrane on CMU and onto metal flashing on the wood-framed curb. A bellows in the air barrier at the roof sheathing-toCMU interface allows movement.
Full references are included in the online version of the article at STRUCTUREmag.org. Tammy Siliznoff M. S., P. E. (CA), is a building and materials science engineer who specializes in failure investigations, existing building retrofits and new construction.
engineer’s NOTEBOOK Shake, Shake, Shake
A beginning primer for a career in civil engineering. By Erin Conaway, P. E., LEED A. P.
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f you are a parent, you know, or will eventually realize, that toys are all-consuming. They take over your home. Your life. Everything. When translated to civil engineering and construction “speak,” they are a critical path to sanity. As such, it becomes crucial to evaluate the value of a proposed toy thoroughly. This is not necessarily the upfront cost, but the value it will bring to your child while factoring in the collateral damage to your mental health (pause here to clean up THAT toy for what seems like the millionth time). The goal, if you wish to proceed with the purchase, is that the toy will keep them blissfully busy—and learning—so you can finish those project calculations you cannot seem to get to and, let’s face it, so that you won’t feel guilty later for Construction of the bridge using gravity and friction. the two hours of cartoons they end up watching. With that goal in mind, this article reviews the Civil Engineer Starter Kit What is in The Box? by KiwiCo through the eyes and experience of a 14-year-old, 10-year-old, and 8-year-old. Also present during testing were There are two detailed instruction booklets, one for a bridge and one two adult electrical engineers (becomes relevant later), one adult for a tower and shake table. structural engineer, one adult mechanical engineer, and an almost The KiwiCo website does an excellent job of illustrating what 5-year-old. Disclaimer: Every kid is different, so proceed while you get when it comes to the parts to build a bridge, tower, and keeping your child and situation in mind. And if you don’t have shake table (dampers included!) and includes a good amount of kids, you might learn something too and have fun doing it! learning literature. The good news is that the literature emphasizes the design process and interviews a “real” engineer! The bad news is that none of the three test subjects paid much attention to the Who Was Into It? learning material. Maybe different results would have occurred if these kids were not on summer break and homework-adverse First off, it must be noted that the 14-year-old showed little during testing. The literature was graphically pleasing, and it is to zero interest in the kit. The 8-year-old was interested and also neat that the company uses kids to test its products in research engaged, although they stated it was “hard” within the first five and development. minutes. The almost five-year-old took a pass to paint instead. But, no harm, no foul! Because the company indicates that the kit is for “plus” 9-year-olds. And the 10-year-old was REALLY The Bridge into it. So, no false advertising here, folks. Assume greater than or equal to nine and less than fourteen is the target for an The 8-year-old was immediately drawn to the bridge. Perhaps engaged user. because these pieces are larger and more solid than the tower’s. O CTO B ER 2023
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The bridge is only held together by gravity and friction and does not require connectors. However, assembly was challenging, and it took two people to accomplish. It was also easily destroyed, leading to much frustration from the 8-year-old. The instruction booklet encourages other ways to “challenge” yourself, such as timed and blind building. None of the kids were interested in doing this, and the bridge was soon abandoned in favor of the tower and shake table.
The Tower The tower is comprised of straw (as in drinking) members and braces, and plastic connectors. Some plumbness (straightness) issues were encountered, and initially, this was frustrating for the 10-year-old, who stated that it “was not perfect” as it was assembled. However, this seemed to be quickly overcome and forgotten as play continued. The connectors are flexible and provide fixed connection points in a radial pattern to allow for the assembly of other shapes, such as spheres. The kit also has a tower base for initial assembly before being transferred to the shake table. The “foundation” consists of velvet twisty ties that could be more robust, in the author’s opinion. Overall, the tower took about 10 minutes to assemble.
The Shake Table Placing diagonal bracing on the tower.
The shake table was the most challenging to assemble and required intervention from an adult. But overall, it is a clever design. It also
Interpreting the directions for the shake table.
Collaborating to test the tower on the shake table.
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includes a motor to enable shaking, complete with an on/off switch. This adds another dimension for kids interested in mechanics and electronics or thinking about creating machines to take over the world. A word of caution is that the kit comes with few, if any, extra parts, meaning that there is not much room for error. The company may intend to simulate a civil engineer’s daily stress about mistakes and material procurement. To that end, the lack of extra parts caused anxiety for the adults who find themselves in those situations regularly, but not for the kids. Accounting for the increased difficulty level, but with fewer parts than the tower, the shake table took about 15 minutes to assemble.
The Test The testing was the best part of the entire experience and allowed for free and creative thinking. The kit includes short and long hangars, with metal washers intended to be used as “dampers.” The adults and kids had fun experimenting with what hangar and damper combination caused the least and most shaking. One feature that would have made it better is the ability to simulate different earthquake magnitudes. This was disappointing mainly for the adults but could be a potential product feature and marketing draw (KiwiCo, I expect a cut of that). It must be noted that, because of the plastic connectors, the tower is not likely to fail. So, you may need to make the point for your child to consider other impacts like occupant comfort and the general implications of a building whip- Gravity-defying engineering feats and tower construction. ping around, which is a difficult concept for a 9-year-old without being able to experience this visually. graphics in the instructions were too small for the detail portrayed Following the original testing, the kids quickly became consumed (which, in hindsight, is an excellent lesson to prepare kids for with adding extra tower stories and creating crazy tower shapes that the real world of civil engineering!). unrealistically defied gravity (future architects?). • Adults liked it too! • Overall, the kit provides good value for the relatively low cost.
Should You Buy It? In summary, here are the key takeaways from this experience: • The tower and shake table are both incredible concepts. • The bridge wasn’t much fun and seemed extraneous, and in the opinion of a building engineer, it suggests that KiwiCo should introduce civil engineering with separate bridge and building kits. • The kit encourages thinking and demonstrates solid engineering principles. • However, the instructions, much like Ikea furniture, were somewhat hard to follow but necessary and didn’t leave much opportunity for the “free thinker.” Many of the figures and
To leave you with one last piece of wisdom, please note that typical household straws could be cut to size and used to create higher towers! The longevity of the kit, at least for this household, is to be determined. However, since testing, the tower and shake table have been whisked away to the 8-year-old’s “secret lab” in the basement, which is a positive sign.■
Erin Conaway, P. E., LEED A. P., is the Senior Director of Market Development with the American Institute of Steel Construction and is based in Denver, CO (conaway@aisc.org).
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historical STRUCTURES 19th Century Mississippi River Bridges #8 Keokuk & Hamilton bridge. By Frank Griggs, Jr., Dist. M. ASCE, D. Eng,. P. E., P. L. S.
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his bridge between Keokuk, Iowa, and Hamilton, Illinois, was one of the eight Mississippi River sites approved by Congress and signed by President Andrew Johnson on July 25, 1866. As such, it had to abide by the requirements for a low-level bridge with a swing span or a high-level bridge with specified horizontal and vertical clearances. The Hancock County Bridge Company received its approval from the Illinois legislature on February 13, 1865, and the Keokuk and Hamilton Mississippi River Bridge Company received its approval from the Iowa Legislature on January 15, 1866. Based upon a survey in 1867, the city of Keokuk in 1868 granted a rightof-way across the levee. T. C. Clarke, the Engineer of the Quincy Bridge (Structure *2022), was named Chief Engineer and prepared a set of plans, estimates, and reports to the Bridge Company in June 1868. The bridge was to carry a single line of the track, two carriageways, and two sidewalks. As such, it was the first multi-modal bridge across the Mississippi. Andrew Carnegie and his associates from the Pennsylvania Railroad, J. Edgar Thomson, and Thomas Scott, invested in the project and, on August 1, 1868, merged the two companies into the Keokuk and Hamilton Bridge Company. They wanted Jacob Hayes Linville as Chief Engineer and for the bridge to be built by the Keystone Bridge Company, in which they were heavily invested. On December 8, 1868, Keystone was awarded the contract for $850,000 to build the superstructure of the bridge, and on January 1, 1869, Linville was named Chief Engineer, and Clarke became a consulting engineer. On January 19, 1869, the following agreement was made between four railroads and the Bridge Company:
This agreement, made and entered into this nineteenth day of January, one thousand eight hundred and sixty-nine, between the Toledo, Peoria and Warsaw Railway Company, party of the first part; the Des Moines Valley Railroad Company, party of
the second part; the Columbus, Chicago and Indiana Central Railway Company, party of the third part; the Toledo, Wabash and Western Railway Company, party of the fourth part, and the Keokuk and Hamilton Bridge Company, party of the fifth part:
Witnesseth, That the party of the fifth part agrees to construct across the Mississippi river, at Keokuk, Iowa, a substantial wroughtiron bridge, which shall be built upon stone piers in accordance with the specifications made by J. H. Linville, chief engineer of the party of the fifth part, and approved by the other parties hereto, suitable for the transit of railway trains; to lay a track upon said bridge, and connect the same with railways belonging to the parties hereto in such manner and at such points as may hereafter be agreed upon. The party of the fifth part further agrees to maintain and keep in repair, in perpetuity, the said bridge and track so that trains may safely cross at all times, except when repairs make it necessary that crossing should be temporarily suspended or when it shall be necessary to have the draw open for the passage of boats. The party of the fifth part hereby grants the parties of the other parts, in perpetuity, the right to use the said bridge to pass its passenger and freight trains across the Mississippi River. The parties of the other part shall have the exclusive right to make the timetable for passing their trains over said bridge.
The party of the fifth part further agrees to begin the construction of said bridge within thirty days from the date hereof and prosecute the work diligently to ensure its completion at the earliest practicable time, not later than January 1st, one thousand eight hundred and seventy. It is understood that said bridge shall be constructed to pass wagons, foot passengers, and general traffic, the revenues from which shall belong exclusively to the party of the fifth part. However, wagons and general traffic shall not be permitted on said bridge during the passage of railroad trains.
Engraving of Keokuk & Hamilton Bridge
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In consideration of which the parties of the first, second, third, and fourth parts agree that they will, in perpetuity, use said bridge for the crossing of their passenger and freight trains and business over the Mississippi River at Keokuk; said crossing to commence
the day the bridge is ready, and to be continued in perpetuity at all times when the bridge is in condition to cross. It also agreed that four parties would pay tolls as part of the agreement for passengers and freight. If the tolls were insufficient to pay operating expenses and interest on the bonds, the four lines would each pay one-quarter of the deficiency. The July 25, 1866, Federal Act stated in section 7,
And be it further enacted That the Keokuk and Hamilton Mississippi Bridge Company, a corporation existing under the laws of the State of Iowa, and the Hancock County Bridge Company, a corporation existing under the laws of the State of Illinois, be and are hereby authorized to construct and maintain a bridge over the Mississippi River between Keokuk, Iowa, and Hamilton, Illinois, of the same character, description, and construction as provided in this act for the bridges at Quincy and Burlington; and the said bridge, in its use and operation, shall be subject to the same restrictions that apply to said bridges at Quincy and Burlington by the terms of this act.
Portal of Swing span
Since it was to be a low-level bridge, it had by the law of 1866 to have a Keokuk with open swing span. swing span with 160´ clearance on both sides of the swing pier and spans of 250´ flanking the swing span in addition to having a vertical clearance of 30´ above low water and 10´ above high water. The bridge as designed was similar to the Dubuque-Dunleith Bridge with a swing span of 376´ 5ʺ (the longest in the world at the time), two spans of 253´ 6ʺ and eight fixed spans-three of 162´ 9ʺ, one of 141´ 4ʺ and four of 164´ 7ʺ - for a total length of bridge of 2,192´; and a width of 21´ 6ʺ center to center of trusses. It had the railroad track down the middle flanked by two carriageways with 5´ sidewalks outside the trusses. Wagons were not allowed on the bridge when trains were crossing. It had the lower chord 10´ above high water set in 1851 and was built on a 17 ½0 skew to better merge with the tracks on both ends of the bridge. The fixed trusses were Whipple Double-intersection trusses (sometimes called Linville Trusses) with vertical end posts (quadrangular) as contrasted with Whipple’s normal inclined end posts. The swing span was a double intersection truss with a curved top chord 35´ deep at the center and 27´ 9ʺ deep at the ends. There was a 200´ long approach with masonry walls on the Keokuk side and a 700´ embankment on the Illinois side.
All spans were fabricated with wrought iron members, with some cast iron junction boxes to join the wrought iron posts fabricated with Keystone compression members. The top compression chords were built up with two I beams and two channels with cover plates. The bottom chords were eye-bar links. The floor beams consisted of two channels trussed with cast iron posts and wrought iron bars. The bridge was finished on April 11, 1870, and the Iowa locomotive crossed the bridge on April 19. A slight mishap occurred when the first locomotive crushed a portion of the swing mechanism, but it was quickly repaired. It was test-loaded on May 18, 1871, by the Pennsylvania Railroad using five Des Moines Valley Railway locomotives weighing 243 ½ tons. All of the tests resulted in deflections of less than 1 ½ʺ. It opened to the public on June 14, 1871, six months after its projected opening. It was replaced with a double-deck bridge by Ralph Modjeski on August 17, 1916, after a life of 45 years.■ Dr. Frank Griggs, Jr. specializes in the restoration of historic bridges, having restored many 19th Century cast and wrought iron bridges. He is now an Independent Consulting Engineer (fgriggsjr@twc.com).
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NCSEA News Congratulations to this Year’s Young Member Scholarship Winners! Each year, NCSEA awards Young Member Scholarships for the NCSEA Structural Engineering Summit. We are pleased to announce the 14 winning young engineers. Their essay responses to the competition question – “What is your opinion about the public’s perception of structural engineers?” – are available at www.ncsea.com/awards. NCSEA thanks Computers & Structures, Inc. (CSI) for sponsoring the travel stipends for this year’s young member scholarship winners and for representatives from the Young Member Group finalists.
Grace Bank
Jennifer Brigante
Nathaly Ciprian
Kamryn Froehle
Kelsey Hammond
Janae Johnston
Benjamin Mall
Douglas McArthur
Austin Norberg
Sohil Paudel
Christian Peterson
Clinton Prier
Stephen Richards
Katherine Rivera
follow @NCSEA on social media for the latest news & events! 70 STRUCTURE magazine
News from the National Council of Structural Engineers Associations Experience the Ultimate Structural Engineering-Focused Exhibit Hall! Join us at the NCSEA Structural Engineering Summit in Anaheim CA, November 7Ð10. Discover the industry’s largest structural engineering-focused Exhibit Hall! Connect with partners, explore cutting-edge products and services, and stay updated on innovations and software enhancements in a lively interactive setting.
NCSEA extends its gratitude to our exhibitors for their support and partnership with the structural engineering community. For details on exhibitors, scan the QR code below or visit ncseasummit.com/exhibit-hall. Don’t miss out! Allen Business Advisors American Concrete Institute (ACI) American Galvanizers Association (AGA) American Ground Screw American Institute of Steel Construction (AISC) American Society of Civil Engineers (ASCE) ArcelorMittal Armatherm ASC Steel Deck Atlas Tube Bentley Systems Blind Bolt Cast Connex CBS2, LLC Chicago Clamp Concrete Reinforcing Steel Institute (CRSI) CoreBrace CTS Cement Dayton Superior DEWALT Dlubal DrJ Engineering LLC
DuraFuse Frames Dymat Inc ENERCALC, LLC Engineers Alliance for the Arts Epoxy Interest Group EPIC Metals Euclid Chemical EVER Seismic LLC Fabreeka Farrell Design-Build FORSE Foundation Technologies Fyfe FRP GERB Vibration Control Systems, Inc. Giza Hilti HYTORC Idea StatiCA International Masonry Institute (IMI) Keller LeJuene Bolt Lindapter LNA Solutions MAX USA CORP
MiTek National Ready Mix Concrete Association New Millennium Nucor Peikko Post Tensioning Institute (PTI) PROSOCO PS=0 Qnect Quick Tie Products QuickFrames RedBuilt Risa Rotho Blaas SAFE-T-PROOF SAFI Structural Technologies SE University (SEU) by SE Solutions Seismic Bracing Company Simpson Strong-Tie SkyCiv SmartLam North America Steel Deck Institute (SDI) Steel Joist Institute (SJI)
Steel Tube Institute Taylor Devices, Inc Tectonus Ltd Think Wood Trimble/Tekla Williams Form Engineering Corp WoodWorks
Exhibitor list as of 9/20/2023. Check the website for any updates.
NCSEA Webinars October 19 November 16 November 28
Visit www.ncsea.com/education for the latest news on upcoming webinars and other virtual events.
Use of the Multi-Period Response Spectrum in ASCE 7-22 Mastering Seismic Design: Answers to the Top 20 Frequently Asked Questions Case Studies in Professional Ethics
Purchase an NCSEA webinar subscription and get access to all the educational content you’ll ever need! Subscribers receive access to a full year’s worth of live NCSEA education webinars (25+) and a recorded library of past webinars (170+) – all developed by leading experts; available whenever, wherever you need them! Courses award 1.0 -1.5 hours of Diamond Review-approved continuing education after completing a quiz. Recommendations for Performing Structural Engineering Quality Assurance Reviews
Recommendations for Performing Structural Engineering Quality Assurance Reviews
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SEI Update Welcome 2023-2024 SEI Board of Governors We are thrilled to announce the SEI Board of Governors set to embark on their term starting October 1st. Their role is vital as we navigate the transition to a new board structure and through SEI’s reorganization. Their expertise will guide us through these changes, ensuring a successful evolution. Give a hearty welcome to the recently elected Board members shown in italics. Here’s to a future marked by collaboration, innovation, and shared accomplishments! Hamid R. Adib, Ph.D., P.E., F.SEI, F.ASCE Michael J. Bolduc, P.E., S.E., M.ASCE Maria M. Garlock, Ph.D., P.E., F.SEI, M.ASCE Jennifer L. Goupil, P.E., F.SEI, F.ASCE, SEI Secretary Jerome F. Hajjar, Ph.D., P.E., F.SEI, F.ASCE, SEI President Edwin T. Huston, P.E., S.E., F.SEI, M.ASCE, SEI Treasurer Chad M. Schrand, P.E., F.SEI, M.ASCE Donald R. Scott, P.E., S.E., F.SEI, F.ASCE, SEI Past President
Kenneth L. Sharpless, P.E., F.SEI, F.ASCE Stephanie L. Slocum, P.E., M.ASCE, SEI President-elect J. Greg Soules, Ph.D., P.E., P.Eng, S.E., F.SEI, F.ASCE Elaina J. Sutley, Ph.D., P.E., M.ASCE James P. Wacker, P.E., M.ASCE Shuxian (Susanne) Wassenius, P.E., F.SEI, M.ASCE Jennifer Zabik, P.E., F.SEI, M.ASCE
And a heartfelt thank you for their service and leadership to the Board members who have finished their terms: John Cleary, Ph.D., P.E., F.SEI, M.ASCE Robin A. Kemper, P.E., LEED AP, ENV SP, F.SEI, Pres.19.ASCE
Takahiko Kimura, P.E., F.SEI, M.ASCE Victor E. Van Santen, P.E., S.E., F.SEI, F.ASCE, SEI Past President
Don Scott’s Past-President Report “It is with great honor and gratitude that I thank you for allowing me to serve as the 2022-23 Structural Engineering Institute’s President. Working with the SEI members, the SEI Board of Governors, and the SEI Staff this year has been rewarding, and together the Institute has made significant progress on many fronts this past year”. – Donald R. Scott, P.E., S.E., F.SEI, F.ASCE
In this moment of transition for SEI we pause to thank Don for his service this year by reading his outgoing report where he reflects on not only the accomplishments achieved under his guidance but aspirations for the future. Join us in extending our heartfelt appreciation and delve into his report to gain insights into the SEI Reorganization and the future of our Standards. https://go.asce.org/45UKtXw
Education
Shine a Spotlight on Excellence: Nominate Your Colleagues by November 1 In the world of structural engineering, innovation and dedication deserve to be celebrated and recognized! Now is your chance to recognize your fellow engineers for their innovative designs, groundbreaking research and unwavering commitment. Nominating a colleague for an ASCE/SEI Award or SEI Fellow is more than just acknowledging their achievements; it’s about celebrating the tireless effort, unwavering commitment, and groundbreaking ideas that have shaped our industry.
Visit www.asce.org/SEIAwards to explore the diverse array of awards available. And don’t forget to check out www.asce.org/SEIMembership to get all the details on SEI Fellow member grade. Award nominations and SEI Fellow applications are due November 1, 2023. Nominate your fellow engineers today and let’s continue to build a future where engineering knows no limits.
Follow SEI on Social Media: 72 STRUCTURE magazine
News of the Structural Engineering Institute of ASCE Advancing the Profession
SEICon24 Technical Program Now Live! Exciting news! The eagerly awaited technical program grid for SEICon24 is now live! Don’t miss your chance to be a part of this cutting-edge event, taking place in San Antonio, Texas from March 20-22, 2024, at NASCC: The Steel Conference. Join us for a unique opportunity to immerse yourself in the world of structural engineering, as you learn, engage, and network with industry experts and peers. Download the technical program grid at www.seicon24.org/program.
LAST CALL for New Members – ASCE 11 Are you looking to get involved in the revision of an ASCE/SEI Standard? The ASCE/SEI 11 Structural Condition Assessment of Existing Buildings Committee is seeking new members to participate in updating this standard. The committee for this cycle will be chaired by Heather Anesta, P.E., S.E. Practicing engineers, researchers, building officials, contractors, and construction product representatives are all needed and welcome. Young professionals are encouraged to apply to participate in this revision effort. If you are interested in applying for this committee please submit your application by October 31, 2023, via the online form. We look forward to your future involvement as the revision for this standard gets underway! https://go.asce.org/ASCE11CallSM
Meet the New Class of ASCE Student Ambassadors Unlock a world of opportunity and connection with ASCE’s latest article featuring our new class of Student Ambassadors. These dynamic ambassadors are the bridge between your campus and the rich realm of ASCE resources. Discover how they’re igniting awareness among students about the abundant offerings ASCE provides post-graduation. These ambassadors are your go-to guides for propelling your growth as a civil engineer. Dive into their journey and tap into the power of a supportive network – read the article now and pave your path to success! https://go.asce.org/3LaH8M6
Support the Future of Structural Engineering – Your Gift Matched 3-to-1! Invest in the future of structural engineering today! Help us maximize the full impact of a Computers & Structures, Inc. match opportunity. Your donation will strengthen our efforts to build a vibrant community of structural engineers. Donate just $10 and the SEI Futures Fund will receive $40! https://go.asce.org/3R9QVWB
Join ASCE to be INSPIRED Join us for ASCE INSPIRE 2023 Conference in Arlington, Virginia to connect with peers, share knowledge, and learn from experts actively bringing the future to life! View the program, register, and learn about sponsor and exhibitor opportunities at inspire.asce.org
Join SEI Today! With link to https://go.asce.org/3L5uqhC
Errata
SEI Standards Supplements and Errata including ASCE 7. See www.asce.org/SEI. To submit errata, contact sei@asce.org. O CTO B ER 2023
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CASE in Point Tools To Help Your Business Grow... CASE has committees that work together to produce specific resources available to members, from contract documents to white papers, to help your business succeed. If you are a member of CASE this tool and all publications are free to you. NCSEA and SEI members receive a discount on publications. Use discount code - NCSEASEI2022 when you check out. Check out some of the brand new CASE Publications developed by the Guidelines CommitteeÉ CASE 976-C: A Review and Commentary on the American Institute of Steel Construction 2022 Code of Standard Practice for Steel Buildings and Bridges The importance of the AISC Code of Standard Practice (AISC 303-22), referred to herein as the Code or COSP) to the construction community is manifested in its almost 100 years of use and development. This Code establishes the trade practices for the steel industry. Generally, this involves the acceptable practices and responsibilities of the Fabricator and Erector and the responsibilities of others such as the Owner’s Designated Representative for Design (ODRD) – (usually the Structural Engineer of Record), the Owner and the Owner’s Designated Representative for Construction (ODRC) – (usually the General Contractor or Construction Manager or similar authority at the jobsite) as they relate to the work of the Fabricator and Erector. The 2022 COSP addresses many recent changes in the practice of designing, purchasing, fabricating and erecting structural steel and is therefore a continuation of the trend of past improvements and developments of this standard. CASE White Paper Beyond the Code: Shrinkage Cracking
CASE recognizes that the International Building Code or other governing codes do not address all aspects of structural engineering and design. Often, the most common issues where the owners, or the contractor or the design team are not aligned deal with what is not clearly addressed by the various codes or design guidelines. This is the second in a series of “Beyond the Code” white papers that will attempt to collate design considerations that need to be discussed with the owners at the beginning of a project to establish a clear Basis-of-Design for the project. By proactively bringing up the design consideration in front of the owners, the Structural Engineer can set up realistic expectations and discuss the cost impact of alternative designs. This white paper in the “Beyond the Code” series discusses shrinkage cracking in concrete with an explanation of why it occurs, common locations they occur, and strategies to mitigate them becoming a risk in your project.
Now more than ever we need to support the upcoming generation of the workforce. Give to the CASE Scholarship today! You can purchase these and other Risk Management Tools at www.acec.org/bookstore. You can also browse all of the CASE publications at www.acec.org/coalitions/coalition-publications/ Is there something missing for your business practice? CASE is committed to publishing the right tools for you. Have an idea? We’d love to hear from you!
Follow ACEC Coalitions on LinkedIn: www.linkedin.com/in/acec-coalitions 74 STRUCTURE magazine
News of the Coalition of American Structural Engineers Upcoming Events Managing Small Projects Successfully: How to Prevent Small Projects from Becoming Big Problems October 31 – November 9, 2023 Online For engineering firm project managers and firm principals, smaller projects can be a core revenue driver. But, smaller projects still have the potential to carry big risk that can be a drag on resources, profitability, and client satisfaction. The good news is that, with the right set of skills in your toolbox, you can ensure that even the smallest projects deliver maximum profits. Register now for Managing Small Projects Successfully: How to Prevent Small Projects from Becoming Big Problems and learn the skills, hacks, secrets, formulas, trouble-shooters and problem-solvers that make engineering firm executives and clients delighted with small project progress and outcomes. From planning, scheduling and budgeting to risk control and crisis management, this live online program packs everything you need into just 8 hours of instruction, broken into two-hour sessions to work with your busy schedule. Even better, it is packed with proven insight from the engineering project management experts at PSMJ Resources, Inc. Earn up to 8 PDHs!
Joint Town Hall Event with CASE, NCSEA, and SEI February 21, 2024 2-3:30pm ET Online Leadership from CASE, NCSEA, and SEI will host a virtual joint town hall event to discuss how the three organizations are progressing to fulfill the Vision for the Future of Structural Engineering (adopted April 2019), highlighting initiatives to advance the profession and enhance member engagement. The town hall is an opportunity to catch up on things you might have missed and gain insight into what the three organizations are doing moving forward. This complimentary event is open to all CASE, NCSEA and SEI members.
https://program.acec.org/ joint-town-hall-event-case-ncsea-and-sei
MEET THE EXECUTIVE COMMITTEE...
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since 1922
2023/24
STRUCTURAL ENGINEERING Resource Guide
Annual Publication with Industry Resources for SEs and Profiles from STRUCTURE’s Advertising Partners
SOFTWARE Canadian Wood Council
ASDIP Structural Software
ENERCALC, LLC
Phone: 407-284-9202 Email: support@asdipsoft.com Web: www.asdipsoft.com Product: ASDIP SUITE Description: Steel,Wood,Masonry,Light Gauge Steel, General Packages Suites,Foundations Retaining Walls, Concrete, CAD, Building Components, Bridges.
Phone: 800-844-1275 Email: sales@woodworks-software.com Web: www.woodworks-software.com Product: WoodWorks Software Description: WoodWorks® Wood Engineering software: Conforms to IBC, ASCE 7, NDS, SDPWS; SHEARWALLS: designs perforated and segmented shearwalls; generates loads; rigid and flexible diaphragm distribution methods. SIZER: designs beams, columns, studs, joists up to 6 stories; automatic load patterning. CONNECTIONS: Wood to: wood, steel or concrete. Canadian version available.
Bentley Systems, Inc.
Dlubal Software, Inc.
Phone: 800-BENTLEY Email: structuralinfo@bentley.com Web: www.bentley.com Product: STAAD Description: Perform comprehensive analysis and design for any size or type of structure faster than ever using STAAD. Simplify your workflow by using a physical model in STAAD that is automatically converted into the analytical model for your structural analysis. Share synchronized models with confidence to deliver safe, cost-effective designs.
Phone: 267-702-2815 Email: info-us@dlubal.com Web: www.dlubal.com Product: RFEM 6 Description: Discover RFEM 6, the cutting-edge structural analysis and design software! With advanced technology, effortlessly create mass timber, concrete, steel, aluminum, cold-formed steel, steel connections, cable, tensile membrane, and CFD wind analysis structures. Get your free 90-day trial at www.dlubal. com now!
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Phone: 800-424-2252 Email: info@enercalc.com Web: https://enercalc.com Product: ENERCALC SEL / ENERCALC 3D Description: ENERCALC includes 42 modules for 90% of your daily engineering design work: Beams (9), Columns (4), Walls (5), Foundations (8), Earth Retention (7), Miscellaneous (5), Analysis (4) and ENERCALC 3D FEM, plus seismic, wind, and snow. Supports wood (including laminated), steel, concrete, masonry, and much more. Cloud/installed with all subscriptions.
Hohmann & Barnard Phone: 800-645-0616 Email: jenniferm@h-b.com Web: h-b.com Product: ProWall Tools Featuring Thermal Brick Support (TBS) Description: Free software for architects, mason contractors, specifiers, and designers, allows users to easily incorporate TBS into projects. Brick support design that can move the shelf angle away from the wall, reducing thermal transfer. Allows fast analysis of a brick support design when entering design parameters into a picture graphic.
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IDEA STATICA
I
Not Just for Steel Anymore
Now with IDEA StatiCa Detail, go beyond traditional methods for the design of discontinuous regions in concrete members and walls. You can see the real structural behavior as well as code checks, deflections, and crack width checks. CSFM (Compatible Stress Field Method) is what makes Detail different. CSFM is an innovative method implemented in IDEA StatiCa concrete solutions used for the design of reinforced concrete structures. Giving you the ability to perform ULS and SLS checks including strength of concrete and reinforcement, anchoring, crack width checks, stress limitation checks. CSFM offers much more than just ULS checks. The advanced state of the art method is based on modified compression field theory, implementation of tension stiffening, and distinguishing between stabilized or non-stabilized cracking. IDEA StatiCa can help you streamline your design as it works with many structural analysis tools (RAM, RISA, TSD, ETABS, SAP, etc.) as well as BIM and detailing software. Unmatched concrete and steel design software that our users confirm that they are saving days and weeks, not only hours on their projects. IDEA StatiCa is a game changer for any Engineer. For more information, please feel free to reach us at:
(856) 642-4070 | office@ideastatica.com | www.ideastatica.com 78 STRUCTURE magazine
ADVERTORIAL
DEA StatiCa is the world-leading solution for the structural design of steel connections, concrete details, and critical members. Our applications enable structural engineers in more the 110 countries worldwide to accurately design structural components, which they had estimated before. We develop software for structural engineers. Our development team researches, evaluates, and applies new methods of analyzing the behavior of structures and their members. Based on this, we create software that enables engineers to work faster, evaluate code requirements thoroughly, and use the optimal amount of material. For us, creating software is a way to contribute to making every project around the world safer, faster, and less expensive. You may know IDEA StatiCa for innovative steel connection software, which helps you design any connection. This versatility means you can explore different configurations of a connection to evaluate time and cost savings for the project.
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COMPUTERS AND STRUCTURES, INC.
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technology. This fueled the proliferation of the software worldwide, especially in developing nations. In 1979 Habibullah and Wilson produced the first 3-D structural analysis modeling application for personal computers. Its powerful numerical methods for earthquake engineering, integrated with new graphics and animation, permanently changed the course of the structural engineering profession. Over the years, CSI has pioneered many developments in algorithms for structural engineering and Finite Element Analysis technology that have addressed challenges that engineers have struggled with for decades. Using the latest and most advanced technology, CSI develops powerful software that directly addresses the needs of the structural engineering community. CSI products are the preferred teaching and research tools in thousands of universities and research organizations, including UC Berkeley, Stanford, Princeton, and MIT. In addition, CSI provides free software to academic institutions in many countries – including Indonesia, Peru, Turkey, and Pakistan – to aid developing countries, specifically in earthquake-prone regions, in producing seismically-resistant structures. Thousands of engineering firms use software from CSI in over 160 countries to design significant projects, including the Taipei 101 Tower in Taiwan, One World Trade Center in New York, the 2008 Olympics Birds Nest Stadium in Beijing, and the cablestayed Centenario Bridge over the Panama Canal. CSI produces five primary software packages: SAP2000, CSiBridge, ETABS, SAFE, and PERFORM-3D.
ADVERTORIAL
omputers and Structures, Inc. develops software for structural and earthquake engineering. CSI’s software is backed by more than four decades of research and development, making it the trusted choice of sophisticated design professionals everywhere. CSI is based in Walnut Creek, California, with offices in New York, Houston, Madrid, New Delhi, and the Caribbean. Through the 1960s and into the 1970s, the University of California at Berkeley campus attracted some of the most brilliant minds in structural engineering. With the space program in full swing and nuclear power plants cropping up all over the country, it was not surprising that UC Berkeley became a hotbed of innovation that resulted in some of the most state-of-the-art computer solutions for complex engineering problems. In 1970, following the development of a series of many unique and innovative numerical methods and algorithms, Dr. Edward L. Wilson, a distinguished professor of structural engineering at UC Berkeley, released the first comprehensive structural analysis computer program – called “SAP: A General Structural Analysis Program.” A revolutionary product that was destined to change the trajectory of engineering analysis forever! Despite the availability of this sophisticated technology, it was not widely used by structural engineers initially. Users were mostly limited to government organizations and large companies. It took a young Berkeley structural engineering graduate, Ashraf Habibullah, to realize that someone needed to deliver the technology to the field. “All this research was being done on campus, but none of it was reaching the profession. So there was a gap between what the researchers were producing and what the professionals could productively use in practice. I knew I could bridge this gap,” said Ashraf. Habibullah approached Wilson and, with his help, created a comprehensive course at UC Berkeley Extension on computeraided structural analysis and design geared toward the practicing structural engineer, with a strong focus on earthquake engineering. The 12-lecture series generated an overwhelming response from the profession. Indeed, there was so much interest that the class had to be moved to a larger venue to accommodate the surge of registrants. Soon after, with growing interest in the technology, Habibullah and Wilson made presentations to packed audiences across the country. In 1975, Habibullah founded Computers & Structures, Inc. (CSI) and positioned the company as a technology transfer link between researchers and professionals, producing practical products based on Dr. Wilson’s original research and work. The advent of personal computers in the late 1970s allowed smaller companies and individuals to access CSI’s powerful
510-649-2248 | sales@csiamerica.com | www.csiamerica.com STRUCTURAL ENGINEERING Resource Guide 2023
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SOFTWARE con’t POSTEN Engineering Systems
RedBuilt
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Phone: 510-275-4750 Email: sales@postensoft.com Web: www.postensoft.com Product: POSTEN Description: The Most Efficient &; Comprehensive Post-tensioned Concrete Software in the world that, unlike other software, not only AUTOMATICALLY Designs the Tendons, Drapes, as well as Columns, but also produces Highly Efficient, Cost Saving, Sustainable Designs with Automatic Documentation of Material Savings for LEED. The others simply Analyze – POSTEN DESIGNS.
Phone: 866-859-6757 Email: info@redbuilt.com Web: www.redbuilt.com Product: RedSpec™ Description: A convenient, user-friendly design program that lets you quickly and efficiently create floor and roof design specifications using Red-I™ joists, RedBuilt™ open-web trusses, RedLam™ LVL, glulam beams, and dimensional lumber. RedSpec is provided free of charge to registered users. For support, contact us by email at RedSpec@RedBuilt.com.
Email: hssinfo@ steeltubeinstitute.org Web: steeltubeinstitute.org Product: HSS Connex Description: A free web-based tool that offers designers a simple way to check HSS wall thicknesses to aid in efficient HSS connection design. These local limit state checks are helpful to ensure HSS wall thicknesses are adequate at connections.
Qnect
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Phone: 413-387-4375 Email: pearl@qnect.com Web: qnect.com Product: QuickQnect Description: QuickQnect is used by EORs to automate the creation of early connected models. Key features of the software include detecting and resolving issues early and rapidly implementing design changes. To learn more about the technology’s latest capabilities, please watch this webinar on our YouTube channel: https://youtu.be/HSRkWzzEnKM
Phone: 949-951-5815 Email: info@risa.com Web: risa.com Product: RISA-3D Description: RISA-3D designs and optimizes steel, concrete, masonry, wood, cold-formed steel and aluminum with a fast, intuitive interface. State of the art solvers, customizable reporting options and robust integration with other products such as RISAFloor, RISAFoundation and Revit make RISA-3D the premier choice for general purpose structural analysis and design.
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Phone: 678-737-7379 Email: jodi.hendrixson@trimble.com Web: www.tekla.com/us Product: Tekla Tedds Description: Automates repetitive and error prone structural and civil calculations, allowing engineers to perform 2-D frame analysis, access a large range of automated structural and civil calculations to U.S. codes, and speed up daily structural calculations. Product: Tekla Structural Designer Description: Engineers have the power to analyze and design multi-material buildings efficiently and cost effectively. Fully automated and packed with unique features for optimized concrete and steel design, Tekla Structural Designer helps engineering businesses win more projects and maximize profits.
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NCEES
ADVERTORIAL
CEES is a national non-profit organization with a mission to advance licensure for engineers and surveyors in order to safeguard the health, safety, and welfare of the public. This mission is supported through its member boards, board of directors, staff, board administrators, and volunteers by: • Providing outstanding nationally normed examinations for engineers and surveyors • Providing uniform model laws and model rules for adoption by the member boards • Promoting professional ethics among all engineers and surveyors • Coordinating with domestic and international organizations to advance licensure of all engineers and surveyors Through education, experience, and exams, professional engineering and surveying licensure establishes an important verification of expertise that is critical in safeguarding the public. NCEES offers more than exams for engineers and surveyors. Through the Records Program, Credentials Evaluations, and CPC Tracking, NCEES is here to help engineers and surveyors
become licensed in multiple states, track continuing professional competency requirements, and to help international professionals become licensed in the United States. Visit www.ncees.org to learn more.
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ENERCALC—A 41-YEAR LEGACY Powerful, Easy-To-Use Structural Engineering Calculation Tools
90% of Structural Engineering Work is Low-Rise To gain perspective on the uses for ENERCALC software, consider your last flight. Before landing, a downtown cluster of skyscrapers, stadiums, and malls appeared. Surrounding them for many square miles are low-rise parking garages, manufacturing facilities, warehouses, retail, hotels, medical complexes, commercial buildings, and other structures that are 90% of structural engineering work. For 41 years, ENERCALC has been committed to supplying structural engineering calculation software for this 90% while retaining simple entry forms with fast recalculation. Today, building codes are complex, with so many load combinations and specific design details that hand calculations are no longer feasible. In addition to the classic structural calculation modules we offered, ENERCALC SEL now includes ENERCALC 3D FEM (a mature, easy-to-use 3-D FEM product) and seven earthretention structure modules. All this in one easy-to-use interface. These modules serve this 90% role completely and are available with budget-friendly subscription pricing.
In a “My office is where I am” world, ENERCALC is everywhere. With a simple, one-price subscription, you can: • Install the software on any computer in any location: ENERCALC automatically manages allowed seat usage. • Launch ENERCALC Cloud and access the same software globally through a browser. It is the same powerful Windows software – not a trivial subset of our desktop software deployed on the web. • Safely and easily share project files between installed and cloud users, thanks to AWS’s secure, redundant global storage network. • Access these applications via your browser from anywhere. Our global network of AWS data centers ensures a great, web-based experience, no matter where you work.
ENERCALC for Revit simplifies structural design by closing the loop between documentation and calculation. It allows engineers to access the familiar power of ENERCALC SEL as a seamless real-time extension of your Revit environment. ENERCALC’S use of the Revit API results in fast-paced, intuitive design with no import/export process. Using ENERCALC for Revit, you can instantly build a complete ENERCALC calculation directly from Revit by simply clicking the element. Create and manage the same detailed structural design calculations you’ve come to rely on but in a fraction of the time. Then automatically update the Revit model from the results of your ENERCALC calculations! Design information automatically pulled from the Revit model – no need for tedious visual inspection, manual measurements, or copy/ paste to build calcs. Calculations are built from physical Revit elements – no need to manage or maintain the revit analytical model! Calculations launch automatically in ENERCALC SEL – no import/export process! Revit model updates instantly – no repetitive modeling work after completing calculations!
ADVERTORIAL
Is Remote Work Important to You?
Is Revit Part of Your Workflow?
A Small Team Working Hard for Structural Engineers ENERCALC – A small, close-knit team focused on simplifying the work of structural and civil engineers.
800-424-2252 | info@enercalc.com | enercalc.com
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BRIDGES American Galvanizers Association
Engineers Alliance for the Arts
RISA Technologies
Phone: 720-554-0900 Email: jkrzywicki@galvanizeit.org Web: https://galvanizeit.org Product: Hot-Dip Galvanized Steel Description: The American Galvanizers Association (AGA) is a non-profit trade association dedicated to serving the needs of after-fabrication galvanizers, fabricators, specifiers, architects, engineers, and contractors. The AGA provides technical support on today’s innovative applications and state-of-the-art technological developments in hot-dip galvanizing for corrosion control.
Phone: 925-482-5500 Email: eaabayarea@gmail.com Web: www.EngineersAlliance.org Product: Student Impact Project Description: We’re on a mission to inspire and educate high school students to pursue an AEC career with our Student Impact Project. EAA offers everything you need to bring our program to your community and help find the next generation of industry leaders. Contact us to help Build A Brighter Future.
Phone: 949-951-5815 Email: info@risa.com Web: risa.com Product: RISA-3D Description: With RISA-3D‚ a versatile modeling environment and intuitive graphic interface you can model any structure from bridges to buildings in minutes. Get the most out of your model with advanced features such as moving loads, dynamic analysis, and over 40 design codes. Structural design has never been so thorough or easy!
POSTEN Engineering Systems
Williams Form Engineering Corp.
ASDIP Structural Software Phone: 407-284-9202 Email: support@asdipsoft.com Web: www.asdipsoft.com Product: ASDIP RETAIN Description: Advanced software for quick and efficient design of cantilever, restrained, counterfort, and sheet pile retaining walls. See immediate results with calculations and reports of load combinations per the latest IBC/ASCE 7 and AASHTO. Includes 4 intuitive modules to help you design and verify structural members.
Phone: 510-275-475 Email: sales@postensoft.com Web: www.postensoft.com Product: POSTEN Description: POSTEN - still the Most Comprehensive, Most Powerful & Most Efficient software for the design of Post-tensioned or Conventionally reinforced concrete structures. No fiddling, guessing or time wasting - the only software that Automatically designs the drapes, prestress and mild steel efficiently the first time.
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FYFE FRP
bidirectional products are available to optimize the performance provided to each structural element. Tyfo Polymer Systems are polymers combined with reinforced fabrics to form advanced composite systems used for structural strengthening. Tyfo® polymer systems are specially formulated to be used in conjunction with the various Tyfo fabrics and prefabricated systems. Our polymers have been optimized to provide convenient working times, excellent indoor air quality, and long-term environmental durability. The type of polymer needed addresses general applications, high-temperature exposure, underwater conditions, and structural strengthening preparation and detailing.
www.FyfeCo.com
ADVERTORIAL
ver time, the stresses of daily wear take its toll on pipelines, bridges, tanks, buildings and other structures. Fyfe® FRP develops and designs materials that strengthen, repair and restore these deteriorating structures—sometimes to better-than-new condition. Founded in 1988 to strengthen failing bridge columns using aerospace materials, Fyfe is a pioneer in the fiber-reinforced polymer (FRP) structural strengthening industry. Today we are a world leader in designing and manufacturing Tyfo®, a system of specialized carbon and glass fabrics, which we combine with polymers to strengthen a wide range of masonry, concrete, steel and timber structures. The Tyfo FRP system is also used to rehabilitate piping systems. Our staff include engineers, designers, material specialists, material manufacturers and project support personnel who work together to develop and design turnkey solutions for structural problems and provide technical support to engineers, contractors and owners in the pipeline, building and bridge rehabilitation markets. Tyfo Composite Systems are advanced composite systems are fiber reinforced polymer (FRP) products specifically made to strengthen structural components. The primary systems are composed of high-strength carbon fibers combined with Tyfo polymers. A variety of unidirectional and
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Phone: 616-866-0815 Email: williams@williamsform.com Web: www.williamsform.com Product: 150 KSI All-Thread-Bar Description: Williams Form Engineering Corpora\on has been providing threaded steel bars and accessories to the bridge construction industry for over 100 years. Williams’ pre-stressing / post tensioning 150 KSI All-Thread-Bars are high tensile steel bars available in seven diameters from 1" to 3" with guaranteed tensile strengths to 1027 kips.
STRUCTURAL ENGINEERING
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CHAMPION FIBERGLASS
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Engineering the Future: Champion Bridge Drain™ – The Essential Solution for Modern Bridge Drainage Systems ensures that it won’t degrade even under constant exposure to sunlight. 6. Easier Field Handling Champion Bridge Drain’s light weight fosters better portability in the field. It offers ease of cutting and integral bell and spigot design that facilitates a simple, fast installation. 7. High-impact Resistance Champion Bridge Drain™ retains its original shape after impact, thanks to its strong and impact-resistant nature. 8. Extended Support Spans Offering extended support spans when compared to conventional PVC systems, Champion Bridge Drain™ saves both labor and material costs over PVC drainage systems that require additional supports. 9. Customization Champion Fiberglass® provides customized solutions, working closely with customers to develop UV-resistant coatings, color matches and other custom features tailored to specific needs. 10. Triple ISO-certified Facility Located in Spring, Texas, the Champion Fiberglass® facility meets all industry standards and certifications, reflecting its commitment to environmental and system management requirements. In addition to being ISO 9001 and 14001 certified, Champion Fiberglass’ occupational health and safety management system has received the ISO 45001 certification for promoting a safe and healthy workplace. 11. Customer Support Since 1988, Champion Fiberglass has been crafting creative solutions for engineers, contractors, and project owners to reach successful outcomes in industrial construction projects with its fiberglass conduit, strut and bridge drain products. The Champion Fiberglass team enjoys assisting engineers and project owners as they build savings and success in their industries.
ADVERTORIAL
oadway bridges and overpasses demand innovative solutions that can withstand the everyday challenges posed by environmental factors and traffic demands. Champion Bridge Drain™ is leading the way as a lightweight, corrosion-resistant and fully customizable drainage solution for bridges. With its line of fittings and nonmetallic accessories, the system presents an elegant answer to drainage problems, suitable for both roadway bridges, freeway overpasses and parking garages. It is becoming the go-to, high-strength solution for engineers desiring to safely clear bridge surfaces of accumulated water. Here’s a detailed exploration of 11 reasons why Champion Bridge Drain™ has become indispensable for bridge projects: 1. Strength and Durability Champion Bridge Drain™ boasts a construction of epoxy resin, promising unparalleled strength, corrosion resistance and flame retardancy. It’s a composite material with a 70% glass to 30% resin ratio, resulting in increased strength, stiffness and impact resistance. Engineered to withstand the harsh conditions of corrosive environments, its remarkable durability contributes to long-term project success and ensures safer driving conditions. 2. Corrosion Resistance Designed with elevated roadway surfaces and bridges in mind, Champion Bridge Drain™ can handle strong contaminants like gas, oil and road salt, making it the ideal system for environmentally challenging drainage scenarios. 3. Light Weight Weighing in at just one-fifth the weight of similar-sized cast iron and PVC systems, Champion Bridge Drain™ eases the dead load on bridges without sacrificing strength, offering a unique balance of efficiency and durability. 4. Lower Installation Costs Contractors enjoy cost-efficient installation benefits. Champion Bridge Drain’s fiberglass components are lighter than steel and simpler to cut, drill and assemble than PVC or steel, resulting in a significant reduction in labor costs. 5. Broad Temperature Range and UV-stable This drainage system can withstand temperatures from −60° to +250° F, allowing for year-round installation. Its UV stability
Are you ready to integrate Champion Bridge Drain™ into your next project? Your next project could be the one that benefits from this leading-edge solution in bridge drainage technology. Contact a local sales representative or get in touch with Champion Fiberglass for detailed insights and personalized assistance.
281-655-8900 | communications@championfiberglass.com | https://championfiberglass.com
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ANCHORS ASDIP Structural Software
ENERCALC, LLC
RISA Technologies
Phone: 407-284-9202 Email: support@asdipsoft.com Web: www.asdipsoft.com Product: ASDIP STEEL Description: Intuitive software for the design of steel members and connections, such as composite/noncomposite beams, steel columns, base plates, anchoring to concrete, shear connections, and moment connections, per the latest design codes. ASDIP STEEL includes 5 modules that substantially simplify the time-consuming calculations of steel and anchor rod structural designs.
Phone: 800-424-2252 or 949-645-0151 Email: info@enercalc.com Web: https://enercalc.com Product: ENERCALC SEL Description: IBC2021 READY! Design of anchors / anchor bolts typically requires a thorough development of applied loads and/or analysis of full structures and connected components. ENERCALC SEL assists in determining those loads and performing those analyses through its Loads & Forces modules and its many analysis / design modules.
Phone: 949 951 5815 Email: info@risa.com Web: risa.com Product: RISAConnection Description: RISAConnection is at the cutting edge of next-generation connection design software and features full 3D visualization as well as expandable reports for every limit state. RISAConnection includes complete integration with RISA-3D and RISAFloor, as well as partner software packages such as Tekla Structures and Hilti Profis for anchorage design.
ClearCalcs
Heckmann Building Products
Phone: 303-309-9444 Email: help@clearcalcs.com Web: https://www2.clearcalcs.com/steelBasePlate Product: Steel Base Plate Design to ACI 318-14 and AISC 360-16 Description: Easily design steel base plates and anchor rods under LRFD analysis. Save 3 hours of calculating by hand with ClearCalcs automated calculations for base plate thickness, and anchor rod effective embedment. You only need to input column sections and loads parameters, and ClearCalcs automates the rest. Try it free: https://bit.ly/3gOp1PZ.
Phone: 800-621-4140 Email: info@heckmannanchors.com Web: www.heckmannanchors.com Product: Masonry Anchors & Ties Description: Heckmann’s has been manufacturing veneer anchoring systems and stone anchors since 1923, Introduced in the mid 1980’s our Pos-I-Tie® Brick Veneer anchor was the first barrel style anchor in the industry. Contact us for additional information.
Williams Form Engineering Corp.
STRUCTURAL ENGINEERING
Resource Guide
Phone: 616-866-0815 Email: williams@williamsform.com Web: www.williamsform.com Product: Anchor Systems Description: Williams Form Engineering Corporation has been providing threaded steel bars and accessories for rock anchors, soil anchors, high capacity concrete anchors, micropiles, tie rods, tiebacks, strand anchors, hollow bar anchors, post tensioning systems, and concrete forming hardware systems in the construction industry for over 100 years.
Profile
WIRE REINFORCEMENT INSTITUTE
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https://wirereinforcementinstitute.org/ | Save Time, Labor and Money 84 STRUCTURE magazine
ADVERTORIAL
he Wire Reinforcement Institute’s (WRI) mission is to promote the specification and usage of welded wire reinforcement (WWR) through the provision of a diverse base of design and construction-related technical resources. Available for free on the WRI website is an expansive library of engineering publications, documents, and online tools for the engineering professional. This resource hub is backed directly by licensed structural engineering support offering thorough technical insights and feedback that are coupled with a strong emphasis on expeditious response time. For WWR design and usage inquiries and interpretations that relate to the entire spectrum of precast and cast-in-place concrete structures, WRI is the technical authority. If you are already using or are considering implementing WWR into your structural designs, reach out to us today.
STRUCTURAL ENGINEERING
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QUICK TIE PRODUCTS, INC. means that it can be used in tight spaces where it was once impossible – or at least a challenge – to install. • For masonry applications, we have developed a patented device to accurately space and support concrete forms. Our QuickTie TM Form Ties secures concrete forms in place while concrete is poured. Importantly for adaptability in the field, Form Ties can be shimmed to level slabs over out of level stem wall. In this way, they provide ease of installation for the foundation contractor, on either stem walls or slabs, prior to his concrete pour. Made out of galvanized steel, Form Ties are designed with rigidity for accurate spacing and support. In addition to our cable system and other proprietary products, we engineer, design and manufacture virtually every structural component needed to build a light wood frame or CMU building – from post bases for your post-to foundation connections, to u-hangers for your joists, up to hurricane clips, straps and wood screws for your truss connections. Our staff of Professional Engineers and designers would love the opportunity to introduce you to our products. Please visit quicktie.com for more information.
ADVERTORIAL
xceptional customer service and innovation drives Quick Tie Products, Inc. (“QuickTieTM”). For 24 years, we have been committed to taking care of our customers, introducing new products, simplifying applications in the field, and providing cost effective solutions for the construction industry. Our core product is the QuickTieTM cable system, a codeapproved engineered system for residential construction that withstands structural uplift and overturning due to hurricane force winds. It is a preferred choice of structural engineers and building professionals for a variety of reasons – two of which are its tattletale nature and inspectability. QuickTieTM cables are tensioned over the specified design load at installation, gradually relaxing. If the system were to fail, it would fail at installation under peak stress. Over-tensioning also compensates for wood shrinkage, cinching a structure to its foundation thereby reducing drywall cracks and nail pops. And QuickTieTM cable anchor embedment depth is 100% verifiable (compared to threaded rod-based systems, where depth is completely unverifiable absent a slab x-ray). Given the choice between threaded rods, conventional holddowns and the QuickTieTM cables, installers overwhelmingly prefer our system to save material conveyance and installation time – and therefore – money. This is particularly true on multistory structures where the cost-conscious engineers and their construction partners heavily favor QuickTieTM cables over the other options. Innovation does not stop with our cable system. Nor is the cable system always a viable option due to required load resistance and constructability issues. Therefore, we are constantly looking for ways to improve operations in the field and maintain structural integrity, and to that end have recently developed several new parts for production in our state-of-the-art manufacturing facility (in Jacksonville, Florida USA) equipped with advanced machinery: • The QuickTieTM Girder Connector (QGC) takes up far less space and, coupled with our cables, can take a heavy uplift load, transferring it from the roof truss girder straight to the foundation. • The SPArtan™ Sill Plate Anchor saves time and money on each job by drilling the sill plate and concrete holes at the same time. Additionally, it requires fewer anchors compared to traditional anchors, has a built-in washer to eliminate assembly and for uplift resistance, and disturbs less concrete when compared to similar strength anchors. The GEOMET® finish provides a superior coating that makes it ideal for exterior and corrosive environments. • Our HD22TM hold down designed to achieve a 22-kip load without the need for through bolts. In addition, our HD22TM has a built-in stand-off which reduces errors during installation. The elimination of through bolts
904-281-0525 | quicktie.com STRUCTURAL ENGINEERING Resource Guide 2023
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CONCRETE ASDIP Structural Software
ENERCALC, LLC
Schöck North America
Phone: 407-284-9202 Email: support@asdipsoft.com Web: www.asdipsoft.com Product: ASDIP CONCRETE Description: Advanced software for the design of multi-span continues beams, biaxial slender columns, concrete/masonry bearing walls, shear walls, one-way slabs and wall opening design, per the latest design codes. ASDIP CONCRETE easily integrates with ETABS and other software to effortlessly maximize your designs with a few clicks.
Phone: 800-424-2252 Email: info@enercalc.com Web: https://enercalc.com Product: ENERCALC SEL / ENERCALC 3D Description: ENERCALC quickly completes calculations for the design of footings, columns, beams, pedestals, slender walls, shear walls, and more. Powerful new quad meshing system simplifies complex mesh building tasks. ENERCALC includes detailed concrete earth retention design / calculation tools. ENERCALC‚ as clear, concise reports are ideal for client/agency reviews. Our 41st year.
Phone: 855-572-4624 Email: info-na@schoeck.com Web: www.schoeck.com Product: Isokorb® Structural Thermal Breaks for concrete applications Description: Schöck Isokorb® structural thermal break solutions both insulate and support structural penetrations through the building envelope including: balconies, canopies, steel beams, slab edges, parapets, solar equipment and HVAC connections. Specialized thermal break modules for concrete-to-concrete, concrete-to-steel and steel-to-steel construction. Assembled in USA.
Dlubal Software, Inc.
RISA Technologies
Phone: 267-702-2815 Email: info-us@dlubal.com Web: www.dlubal.com Product: RFEM 6 Description: Discover RFEM 6, your all-in-one solution for reinforced concrete projects! Enjoy member, wall, and slab design compliant with ACI 318 and international standards. View detailed, traceable design results including 3D column interaction diagrams and design formulas. Get your free 90-day trial at www.dlubal.com now!
Phone: 949-951-5815 Email: info@risa.com Web: risa.com Product: ADAPT-Builder Description: ADAPT-Builder is powerful and easy-to-use 3D finite element software for multistory reinforced concrete and post-tensioned buildings and structures. Builder delivers comprehensive workflows for complete analysis and design. Combine gravity, lateral and post-tensioning actions for efficient, complete, and accurate design. Integrate with various BIM software for seamless project deliverables.
Williams Form Engineering Corp.
STRUCTURAL ENGINEERING
Resource Guide
Phone: 616-866-0815 Email: williams@williamsform.com Web: www.williamsform.com Product: Anchor Systems Description: Williams Form Engineering Corporation has been providing threaded steel bars and accessories for rock anchors, soil anchors, high capacity concrete anchors, micropiles, tie rods, tiebacks, strand anchors, hollow bar anchors, post tensioning systems, and concrete forming hardware systems in the construction industry for over 100 years.
Profile
CTS CEMENT MANUFACTURING CORP. Fast, Hard, Durable, and Easier on the Environment
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ADVERTORIAL
CTS Cement manufactures two lower-carbon alternatives to portRapid Set Cement is the core land cement for the construction and restoration of building and ingredient in dozens of cements, infrastructure structural components: Rapid Set® Cement and mortars, and grouts engineered specifically for the strength requirements Komponent® shrinkage-compensating additive. Both brands are a of floors, walls, columns, beams, piles, and other structural components. type of calcium sulfoaluminate (CSA) cement, which emits 33% Komponent is a shrinkage-compensating additive blended with local less CO2 during manufacture than portland cement. In 2022, a portland cement and aggregates to make ASTM C845-compliant Type III environmental product declaration (EPD) was developed Type K shrinkage-compensating concrete and grouts for transportafor each brand to support project owners’ efforts to use sustainable tion, tunnel, water and wastewater containment, industrial floor, and building materials. commercial building. In addition to thwarting curling and cracking Rapid Set Cement qualifies as very rapid hardening (VRH) per caused by drying shrinkage, the additive enables design engineers to ASTM 1600 (Standard Specification for Rapid Hardening Hydraulic reduce or eliminate control joints significantly. Cement) and can achieve 4500 psi compressive strength at 1.5 hours. Rapid Set Cement- and Komponent-based products have been used Unlike other CSA cements, it doesn’t require blending with portland to build such landmarks as the Hoover Dam Bypass, the Pentagon, cement or accelerators. Mixed, placed, and finished similarly to the Lincoln Tunnel, and the San Francisco-Oakland Bay Bridge, as portland cement concrete, the material saves time and money during well as major roadways, airports, commercial, and industrial projects construction by lowering installation times and labor requirements. worldwide. Research by departments of transportation (DOTs) As a CSA cement, Rapid Set is inherently more resistant than nationwide confirms the durability of decades-old placements. portland cement to deterioration caused by chlorides, alkali-silica Our team of material scientists, engineers, technical experts, and reaction (ASR), sulfate attack, and shrinkage cracking. As a result, field representatives work with you every step of the way, from design major structural components require less maintenance and repair, through construction, to ensure your success. Contact us for assistance lowering overall lifecycle costs. with product selection, specifications, samples, and mix designs. 800-929-3030 | info@ctscement.com | www.ctscement.com
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RISA TECHNOLOGIES
ISA delivers a suite of integrated software design solutions and technical support services that allow structural engineers to innovate with confidence, secure in the safety and efficiency of their designs. The following case studies illustrate these core values.
Academy Museum of Motion Pictures
Carson Group Omaha Headquarters Building Client: Carson Groupl Structural Engineer: LEO A DALY, Omaha, NE Carson Group’s Omaha HQ prioritizes open, cultural office space across two buildings connected by an amenity hub and sky-bridge. Transparent glass envelopes underscore both financial trust and a 35-year Omaha connection, while amenities like a rooftop bar attract other companies to the 200,000 SF workspace. Prominent in the building’s profiles are the distinctive upward-sweeping roofs, resembling financial growth curves and enclosing mechanical systems. The steel canopy, devoid of metal deck for lateral forces, relies on a bracing system designed by LEO A DALY engineers. The monumental
Orange County Museum of Art Building Client: Orange County Museum of Art Structural Engineer: John A. Martin & Associates, Inc., Costa Mesa, CA The new Orange County Museum of Art spans 53,000 sq ft, housing exhibition galleries, educational programs, and public gathering spaces. As part of the Segerstrom Center for the Arts campus, the museum adds to its integrated complex. With a focus on a multi-story glass atrium, the museum features a sculptural exterior design that facilitates adaptable gallery space. Combining concrete and steel, the intentional exposure of these materials by the architect adds character to the building’s structure. The Orange County Museum of Art’s intricate form posed an exhilarating engineering challenge. Structural firm JAMA and architect Morphosis collaborated closely to situate steel framing for the distinctive angles, demanding design iterations and quick adaptability. JAMA meticulously reassessed each iteration to ensure stability given complex load paths. The building comprises three parts: a flexible steel-framed classroom, a rigid concrete main gallery, and a glass atrium with spanning bridges. Despite differing lateral systems, connectivity was achieved across the atrium without seismic joints, utilizing steel beams within the glass bridges and as seismic struts for the atrium. JAMA relies on RISA-3D for structural design. The software’s rapid modeling facilitated diverse design versions for classrooms, the “Plantilever,” and steel trusses. DXF import converted Rhino model iterations swiftly. RISA-3D’s unique tools like spreadsheets and node manipulation, uncommon elsewhere, empowered edits. The significant “Plantilever,” supporting a rooftop garden, crowns the museum’s northeast entrance above the window gallery. Sloping columns merge into 5ft deep plate girders at the entrance’s north, constituting the cantilever. RISASection created the built-up plate girder section, imported into RISA-3D for 32-ft cantilever analysis.
ADVERTORIAL
Building Client: Academy of Motion Picture Arts and Sciences Structural Engineer: Buro Happold, Los Angeles, CA The Academy Museum blends a cinema museum, theater, and historic restoration. It rejuvenates the Saban Building and links to the unique Geffen Theater through three bridges, uniting tradition and innovation. The project also fosters public spaces connecting neighboring Miracle Mile institutions. Linking the historic Saban Building to the new Geffen Theater posed a formidable challenge for structural engineers Buro Happold. The Geffen addition adopted a distinct lateral force system—base-isolators. Retrofitting the original Saban Building with this system was infeasible, requiring lateral enhancements for seismic compliance. These upgrades involved reinforcing existing steel framing, introducing concrete shear walls, and collectors. Despite disparate lateral systems, the buildings needed cohesion through three bridges and exterior stairs. Flexible connections, including custom universal hinges developed with CastConnex, addressed these interface needs effectively. Buro Happold relied on RISA-3D’s crucial analysis output for designing three pedestrian bridges that connect old and new buildings. RISA-3D’s transparency in member analysis was vital, enabling the creation of custom hinge connections for stairs connecting the base-isolated Geffen Theater to the stable ground, accommodating the 30-inch structure movement. This demanded incorporation of substantial P-delta effects in RISA-3D’s finite-element analysis. The software’s versatile reporting, member releases, and P-delta considerations ensured an accurate and efficient representation of the unique structural demands.
stair presented a structural challenge, balancing vibrations and architectural finesse. This stair links the lobby and amenity hub, visible from outside, demanding a sleek profile. RISA-3D aided in meeting performance and architectural constraints for this demanding design. LEO A DALY employed RISA-3D for intricate zones like the “sit-stair,” rooftop canopies, and sky-bridge. This software facilitated quick, accurate static and dynamic analysis, aiding understanding of interactions with the main structure. Acting as architect and engineer, LEO A DALY valued RISA-3D’s flexibility for seamless collaboration, especially during the 2020 pandemic, helping with steel member procurement challenges.
949-951-5815 | info@risa.com | risa.com STRUCTURAL ENGINEERING Resource Guide 2023
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FOUNDATIONS Altair
ClearCalcs
RISA Technologies
Phone: 604-273-7737 Email: manishaw@altair.com Web: www.altair.com/s-concrete Product: Altair S-CONCRETE Description: S-CONCRETE quickly and accurately designs reinforced concrete column, beam, wall sections, and continuous beams to regional code requirements. Versatile and easy-to-use for any project workflow, users save time by automatically checking thousands of concrete designs at once to produce comprehensive design reports.
Phone: 303-309-9444 Email: help@clearcalcs.com Web: www2.clearcalcs.com/retainingwallcantileverUSA Product: Cantilever Retaining Wall Calculator to IBC 2018, ASCE 7-16 Description: ClearCalcs offers fast, customizable cantilever retaining wall design and analysis calculations for IBC. The easy-to-use interface makes it effortless to input your soil report information or use presumptive values if you do not have access to a soil report. Try it for free for 14-days at https://bit.ly/3SJxt05.
Phone: 949-951-5815 Email: info@risa.com Web: risa.com Product: RISAFoundation Description: RISAFoundation is the ultimate tool for analysis and design of a variety of different foundation types. Featuring an open modeling environment, finite element analysis, and full integration with superstructure analysis programs; you won’t find a better choice for retaining wall, spread footing, combined footing, mat slab, or pile cap design.
ASDIP Structural Software
ENERCALC, LLC
Williams Form Engineering Corp.
Phone: 407-284-9202 Email: support@asdipsoft.com Web: www.asdipsoft.com Product: ASDIP FOUNDATION Description: Intuitive software for quick and efficient design of concrete footings, such as isolated spread footings, two-column combined footings, strap footings, wall footings, and pile caps. See immediate graphical results, calculations, and detailed or condensed reports with exposed formulas and code references. ASDIP FOUNDATION easily integrates with ETABS and other software.
Phone: 800-424-2252 Email: info@enercalc.com Web: https://enercalc.com Product: ENERCALC SEL / ENERCALC 3D Description: ENERCALC has you covered when it comes to design of individual pad footings, continuous wall footings, or combined footings. The foundation design modules feature flexible geometry definition, thorough load combinations, and clear concise output. Instant recalculation allows you to test‚“what-if‚” solutions. Check out ENERCALC’s FEM footing design capabilities today!
STRUCTURAL ENGINEERING
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Phone: 616-866-0815 Email: williams@williamsform.com Web: www.williamsform.com Product: Anchor Systems Description: Williams Form Engineering Corporation has been providing threaded steel bars and accessories for rock anchors, soil anchors, high capacity concrete anchors, micropiles, tie rods, tiebacks, strand anchors, hollow bar anchors, post tensioning systems, and concrete forming hardware systems in the construction industry for over 100 years.
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Reduce Costs Pouring back pour strips is the most expensive concrete poured on a job. Formwork, shoring, and backshoring must stay in place for weeks, and crews must reassemble for small pours. The PS=Ø® system eliminates this costly and timeconsuming step.
Accelerate Construction Pour strips delay construction schedules. They not only require pouring back the leave-out, but also restrict worker access. By eliminating pour strips, the PS=Ø® system cuts months off construction schedules.
Improve Safety An open leave-out in a floor is a major safety hazard. Pour strips are particularly hazardous because they run the entire width of the slab and are impossible to avoid. The PS=Ø® system replaces dangerous leave-outs with a narrow, grouted joint.
Quality Concrete Without needing an open pour strip leave-out, engineers can now achieve higher quality concrete by specifying longer leave-out times, releasing stiff elements without causing delays or increasing cost.
800-355-8414 | sales@pourstrip0.com | www.pourstrip0.com 88 STRUCTURE magazine
ADVERTORIAL
liminate pour strips, wall restraint, and expansion joints – and the extra costs, construction delays, and safety issues they bring – with the PS=Ø® Mechanical Reinforcement Splice System. The PS=Ø® Mechanical Reinforcement Splice System eliminates pour strips, wall restraint, and expansion joints while allowing for volume change in the slab and providing structural integrity. Using proven coupler technologies recognized worldwide, the PS=Ø® system features a thread on one end and a grout-filled sleeve on the other. The system is an ACI-permitted Type 1 and Type 2 mechanical splice, ICC-approved, and made in the USA.
STRUCTURAL ENGINEERING
Resource Guide
Profile
LYNCH MYKINS
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Humanity Isn’t Optional: Successful SE Companies are People-First
ou can have state-of-theart software, the latest tools and gadgets, top-notch resources and suppliers, and the excitement of big and complex projects. But, if you don’t have happy engineers who are excited about relating to them, creating with them, communicating with them, and capable of presenting the value of their ideas to clients with confidence, does state-of-the-art even matter? It’s a means to an end. You already know the structural engineering industry is Anna Lynch, P. E., CEO challenged with bringing fresh Lynch Mykins Structural Engineers talent into it and keeping them. Over the past 7 years, under the leadership of CEO, Anna Lynch, Lynch Mykins Structural Engineers has been focused on creating and nurturing a people-first culture that attracts fresh talent and has reduced attrition rates lower than the industry average. Today, engineers in the U.S. have incredible opportunities to leave their mark with heart, fun memories, joy, and pride in the places they’re building. We’re not talking about the future of structural engineering. We’re talking about today. Now. We’re talking about proven facts like humans are wired for connection, laughing reduces stress, and social interaction is a basic human need like food and water. Knowing this and believing that a traditionally stressful industry can be flipped on its side, Anna deconstructed the journey of a structural engineer’s role, growth, and development. Then, she redesigned it and reinvented her 49-year-old firm, with a keen eye on the goal of thriving people and thriving business for decades to come. It didn’t happen overnight, but it did happen quickly and intentionally. With care, research, communication, and heart-led leadership, the company has created one of the most unique external brands, with an internal people-first culture that fully supports it!
How Lynch Mykins employees experience a people-first culture:
Email us at culturecoaching@lynchmykins.com to get our FREE CULTURE IDEAS for SE firms to get you started!
Lynch Mykins’ “people-before-profit” commitment is demonstrated by their investment in the individual employees to help them become the best person, and engineer they can be. When people feel supported, happy, and connected, profits always result - now, and ten years from now. In our hard skills world, the left brain is no longer enough. Successful engineers are learning strategies to practice using the whole mind to be their best with clients and each other. At Lynch Mykins, human connection and creativity upstage perfection every day of the week!
“In a people-first company, diverse thinking leads naturally to accepting diversity in every way - people, ideas, dress, projects, conversation. I’m no longer held back by who I am. I’m respected, appreciated and I’m growing without limits now. When people are allowed to be real, clients get real ideas, real conversation, real connection, and creativity. Not some distant, overly processed, uncomfortable attempt at trying to be something they’re not.” “This industry can be stressful, so Lynch Mykins has figured out a ton of ways to reduce the stress and make it fun. We have Happy Hours, a nap room, ping-pong and pool tables. No one dreads Mondays because in our Monday morning meetings, we lift each other up, shout-out each others’ victories, share upcoming events and lessons learned. It really does feel like a family that truly wants the best for everyone!”
Chris Cobb, Senior Project Manager, Raleigh, NC
Nicole Zechman, Design
ADVERTORIAL
If you’re not interested in building a culture from scratch, hello! Consider joining ours! Scan this QR code and see if we have the perfect job for you.
“Just because we’re engineers doesn’t mean we need to perpetuate the stereotype of engineers. It’s refreshing to work with a CEO who’s in it for the right reasons, encourages us to be ourselves, and provides us with the support and personal development to do it with confidence. I moved across the country for this and I love laughing, playing music, dancing, high-fiving coworkers in a place where work is fun.”
Director, Charlotte, NC
Victor Torres, Project Engineer, Richmond, VA
lynchmykins.com
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STEEL Bull Moose Tube
ClearCalcs Pty Ltd
Phone: 720-554-0900 Email: aga@galvanizeit.org Web: https://galvanizeit.org Product: Hot-Dip Galvanized Steel Description: The American Galvanizers Association (AGA) is a non-profit trade association dedicated to serving the needs of after-fabrication galvanizers, fabricators, specifiers, architects, engineers, and contractors. The AGA provides technical support on today’s innovative applications and state-of-the-art technological developments in hot-dip galvanizing for corrosion control.
Phone: 800-325-4467 Email: john.phillipp@bullmooseindustries.com Web: www.bullmoosetube.com Product: Hollow Structural Sections, Pipe Pile, Sprinkler Pipe, and Mechanical Tubing Description: Specializing in HSS, sprinkler pipe, mechanical steel tube, and pipe pile, BULL MOOSE TUBE provides steel pipe & tube for nearly any application. Our capabilities allow us to manufacture one of the industry’s largest size ranges - up to 14ʺ square, 18ʺ round, and 0.750ʺ wall.
Phone: 303-309-9444 Email: help@clearcalcs.com Web: https://clearcalcs.com/ Product: Steel and Cold-Formed Steel Beam & Column Calculators to AISC 360-16 and AISI S100-2016 Description: ClearCalcs offers fast, customizable steel and cold-formed steel beam and column calculators to ASD or LRFD provisions to AISC 360-16 and AISI S100-2016. Model any type of beams or columns with a handy range of presets that save you time. Try it for free for 14 days at https://bit.ly/3GvEMoR.
ASDIP Structural Software
Cast Connex
Dlubal Software, Inc.
Phone: 888-681-8786 Email: info@castconnex.com Web: www.castconnex.com Product: Standardized Cast Steel Connectors and Custom Cast Steel Connectors Description: The industry leader in the architectural and structural use of cast steel components in the design and construction of building and bridge structures. Our products include pre-engineered connectors that simplify the design and enhance the performance of structures. We also offer design-build services for custom cast steel nodes and components.
Phone: 267-702-2815 Email: info-us@dlubal.com Web: www.dlubal.com Product: RFEM 6 Description: Experience RFEM 6, the advanced structural design software. Design steel and cold-formed steel members following AISC and AISI standards or integrate with other materials for hybrid structures. Utilize the all-new FEAbased steel connection design for standard to complex connections. Get your free 90-day trial at www.dlubal.com!
American Galvanizers Association
Phone: 407-284-9202 Email: support@asdipsoft.com Web: www.asdipsoft.com Product: ASDIP STEEL Description: Intuitive software for the design of steel members and connections, such as composite/ non-composite beams, steel columns, base plates, anchoring to concrete, shear connections, and moment connections, per the latest design codes. ASDIP STEEL includes 5 modules that substantially simplify the timeconsuming calculations of steel structural designs.
STRUCTURAL ENGINEERING
Resource Guide
Profile
ASC STEEL DECK
Innovators of engineered steel roof & floor deck solutions
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90 STRUCTURE magazine
ADVERTORIAL
erving the Western United States since the 1970s, ASC Steel Deck allowing for composite is a leading manufacturer of high-quality structural steel deck solu- design. Smooth Series is tions for the building and construction industry. Based in Kalama, WA, ideal for exposed applicaASC Steel Deck continues to advance the steel deck industry through tions where the underside innovation and an unmatched commitment to customer success. of the deck will be visible. ASC Steel Deck can supply products with a range of metal thicknesses, In addition to manufacturing steel roof and floor deck products, ASC galvanized coating weights, paint finishes, and perforation options to meet Steel Deck seeks to improve the installation process to help keep costs low all project requirements, including pre-primed to save installation labor through innovations. Key innovations include the DeltaGrip® DG4™ Tool, costs. ASC Steel Deck’s product line covers the scope of shallow to deep a mechanical side-seam attachment system that reduces the installation rib configurations and standard to high-strength offerings. These products costs of high-shear diaphragms by eliminating costly top seam welds. are featured in high-profile projects, including stadiums, warehouses, This revolutionary structural sidelap connection system for steel roof deck office buildings, and airports. applications builds upon the original DeltaGrip System by introducing One of ASC Steel Deck’s most unique offerings is its propriety cellular the added benefits of higher connection strength, faster cycle times, and deck option, such as the Smooth Series™ product line. Smooth Series increased punch durability. features a clean beam-to-pan With a focus on making project design easier for customers, ASC rivet-attached flat pan under- Steel Deck provides BIM tools, design software libraries, and product side, eliminating unsightly burn samples to support project teams. By continuously advancing steel deck marks created by traditional technology, ASC Steel Deck enables architects, engineers, and contracwelded attachments. This cre- tors to maximize value and performance. Their full range of steel roof ates an aesthetically pleasing, and floor deck products offers economical, high-performance options blemish-free appearance while for any building project. 800-726-2727 | info@ascsd.com | www.ascsd.com
STRUCTURAL ENGINEERING
Resource Guide
Profile
ALTAS TUBE Scale and Speed Without Sacrifice
T
ADVERTORIAL
oday’s construction and development industry is one that built-up boxes can save valuable shop hours when labor is tight. saddles a building’s designers and fabricators with a barrage Jumbo HSS also have 50% less surface area than wide-flange secof challenges that threaten to compromise their vision. A volatile tions, further reducing prep and finishing time and costs. economic climate, unpredictable supply Big in size. Small on environmental chain issues and rising material costs have impact. In addition to their unique size a chokehold on budgets and resources. and strength, one of the biggest appeals The wave of retirees coupled with a of Jumbo HSS is their low environmental shortage of incoming skilled tradespeofootprint. Steel is an endlessly recyclable ple frequently leads to understaffed job material, which, when combined with the sites and scheduling delays. Increasingly low-profile design of HSS and Atlas Tube’s stringent environmental building and sustainable manufacturing practices, can manufacturing regulations can drive up help lower a project’s embodied carbon. already strained budgets. In the face of Roughly 70% of HSS in North America these challenges, architects, engineers, are produced using electric arc furnace (EAF) contractors and fabricators are thinking steel coils and Atlas Tube exclusively purcreatively and looking for out-of-the-box The largest domestically manufactured Jumbo HSS are chases steel from North America, which has solutions to deliver on the project’s vision. available in a variety of sizes with wall thickness up to 1”. among the lowest carbon emissions of the Supporting the design possibilities. leading steel manufacturing regions. In fact, Atlas Tube is a domestic manufacturer helping builders meet steel production in the U.S. produces 60% fewer greenhouse gas emissions the challenges of today by innovating new solutions, expanding than in China, a top steel exporter to the U.S. Atlas Tube’s manufacturing existing product offerings and delivering on-time for the most facilities are also continually optimizing energy usage and minimizing demanding project schedules and budgets. wastewater, while ensuring that all steel scrap is recycled. Nothing exemplifies this more than two Atlas Tube products, Connections made easy. Now the on-site fabrication of HSS can be Jumbo HSS and Shuriken. Each of these products was specifically more streamlined thanks to Shuriken, the Better Bolted Connection — designed to help engineers, builders and fabricators overcome the an innovative connection solution for situations where field welding is challenges they face without having to make sacrifices in their not possible. Shuriken has a built-in wrench that allows steel fabricators designs. North America’s largest HSS and Shuriken Better Bolted and erectors to quickly and easily field bolt HSS columns, beams and Connections allow builders to design on a larger scale while at the trusses; wide-flange sections; SpeedCore; connections in tight spaces; same time addressing labor and material cost challenges. pedestrian bridges; and retrofits. Fewer field welds, easier installation, Build bigger, wider, taller. As the largest domestically manufac- faster visual inspections and lower costs help make HSS a more costtured HSS in North America, Jumbo HSS offer up the highest effective and efficient option than ever before. strength-to-weight ratio of any structural Dream big, design big with Jumbo HSS steel available. That means wider spans and Shuriken. Stronger, more innovative, with less steel for today’s largest applicamore sustainable building materials like tions, like factories, warehouses, airport Jumbo HSS and Shuriken make it poshangars, data centers, bridges, skyscrapsible to continue designing and building ers and more. Their smaller, stronger for the future while facing the challenges footprint and aesthetically appealing of today. To learn more about either proddesign compared to wide-flange sections uct, including Shuriken’s new 1” size, visit allow engineers to support the demand atlastube.com for more open, better-utilized spaces. A shared vision. Atlas Tube is part of Efficiency is key. The high strength-toZekelman Industries — a family of domesweight ratio and size of Jumbo HSS (up tic manufacturers striving to help builders to 28” square with 1” wall thickness) Field bolt Jumbo HSS with Shuriken. meet the challenges of today by delivering creates the potential to use less steel in a new, better ways to build. Their shared project, resulting in time, labor and cost efficiency gains — critically vision of operational excellence and best-in-class customer service important given the labor shortage and fluctuating material costs. make them the partners of choice for those with big aspirations. To And for fabricators, the opportunity to use Jumbo HSS instead of learn more about Zekelman Industries, visit zekelman.com atlastube.com
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STEEL con’t ENERCALC, LLCA
New Millennium
Schöck North America
Phone: 800-424-2252 Email: info@enercalc.com Web: https://enercalc.com Product: ENERCALC SEL / ENERCALC 3D Description: Save hours on every steel design with ENERCALC – now with FEM capabilities. Beams, columns, two dimensional frames, force distribution in bolt groups and more. The clear, simple user interface makes it fast & easy to setup, confirm & “what-if ” your designs. Member optimization improves your efficiency and saves time!
Phone: 260-969-3500 Email: sales@newmill.com Web: www.newmill.com Product: Steel Joists and Deck Description: Achieve architectural visions. Solve engineering challenges. Realize project goals. Your success begins with the selection of the right steel building system. We have the expertise to help you determine the optimal structural steel building system for your application. From steel joists and deck to long-span composite floor systems, we engineer and manufacture solutions that control costs, enhance performance and ensure project success. Together, let’s build it better.
Phone: 855-572-4625 Email: info-na@schoeck.com Web: www.schoeck.com Product: Isokorb® Structural Thermal Breaks for steel applications Description: Schöck Isokorb® structural thermal break solutions both insulate and support structural penetrations through the building envelope including: balconies, canopies, steel beams, slab edges, parapets, solar equipment and HVAC connections. Specialized thermal break modules for concrete-to-concrete, concrete-to-steel and steel-to-steel construction. Assembled in USA.
LeJeune Bolt Company
RISA Technologies
Phone: 952-843-5445 Email: jcaven@lejeunebolt.com Web: www.lejeunebolt.com Product: Torque and Angle ASTM F3148 fastening system Description: Bolt size from 5/8 to 1 1/8. Please get in touch with me for additional details!
Phone: 949-951-5815 Email: info@risa.com Web: risa.com Product: RISA-3D Description: RISA-3D is the best choice for the design of all things steel. Whether designing custom hot rolled steel shapes or cold-formed steel wall panels, RISA-3D has you covered. With steel databases and design codes from all over the world, you’ll never have to look anywhere else.
Williams Form Engineering Corp.
STRUCTURAL ENGINEERING
Resource Guide
Phone: 616-866-0815 Email: williams@williamsform.com Web: www.williamsform.com Product: 150 KSI All-Thread-Bar Description: Williams Form Engineering Corporation has been providing threaded steel bars and accessories to the bridge construction industry for over 100 years. Williams’ pre-stressing / post tensioning 150 KSI All-Thread-Bars are high tensile steel bars available in seven diameters from 1" to 3" with guaranteed tensile strengths to 1027 kips.
Profile
ICC EVALUATION SERVICE
I
92 STRUCTURE magazine
ADVERTORIAL
CC Evaluation Service (ICCmanufacturers, ICC-ES provides inspection, testing, and certiES) is the industry leader in fication for manufacturers worldwide. Testing is available for a performing technical evaluations wide range of building and plumbing products. ICC-ES offers of building products, materials, manufacturers a streamlined process from testing to inspection and systems for code compliance. to certification, saving time, money, and resources to increase Due to its diligence and unparalleled engineering experience, speed to market. ICC-ES is the nation’s most widely accepted evaluation agency. ICC-ES Evaluation Reports (ESRs), Building Product Listings Known for its expertise in code compliance and the development (ESLs), and PMG Listings provide evidence that products and of Acceptance Criteria for new innovative products, code officials systems meet requirements of codes and technical standards worldwidely accept and trust ICC-ES reports and listings. wide, including the US, Canada, Mexico, Australia, New Zealand, ICC-ES is accredited by ANSI National Accreditation Board and the MENA region. (ANAB) to the requirement of ISO/IEC 17065, Standards Council Look for the ICC-ES Mark of Conformity on various building, of Canada (SCC), and Entidad Mexicana de Acreditación, A.C plumbing, mechanical, swimming pool and (ema) for Mexico. With over 90 years of experience and thousands spa, and fuel gas products. Once an ICC-ES of reports, ICC-ES is trusted by manufacturers, building officials, evaluation report is issued, a manufacturer can engineers, specifiers, and architects. Manufacturers use the reports apply the ICC-ES mark to their product as as evidence that their products meet code requirements and war- evidence of compliance to the latest applicable rant regulatory approval. codes and standards which can help streamline ICC-ES also has certification programs for plumbing, mechanical, the approval process for installation. Contact us today to learn and fuel gas (PMG) products, solar heating and cooling products, more about our product certification services. food safety and quality, and green building products. As a total conformity assessment solution service provider for 800-423-6587 | es@icc-es.org | www.icc-es.org
STRUCTURAL ENGINEERING
Resource Guide
Profile
NEW MILLENNIUM
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Building Success with Steel Joists and Deck
ew Millennium is your collaborative partner for the design, engineering, and supply of structural steel joist and roof and floor deck solutions for commercial steel construction. A wholly owned subsidiary of Steel Dynamics Inc. with seven manufacturing facilities across North America and local sales teams near you, we stand ready to meet your project needs. We assist you right from the start in specifying and engineering the steel joists and steel deck best suited for your design and application. We engineer and manufacture solutions that control costs, enhance performance and ensure project success.
Custom-fabricated steel joists and joist girders
Steel roof and floor deck New Millennium manufactures a range of steel roof and floor deck profiles to address your structural and architectural needs. Our new IMPRESSIONS™ steel deck combines wood’s natural beauty with the strength of steel. A structural roof deck using our Versa-Dek® profile, IMPRESSIONS features digitally printed wood-grain finishes so realistic you won’t believe it’s steel. Steel roof can be installed with exposed structural frames to create striking, spacious interiors and dramatic, high-performing exteriors. Optional acoustical treatments absorb sound energy. Applications readily integrate lighting, electrical, plumbing and fire suppression systems. For multi-story construction, long-span composite floor deck addresses multiple factors, including total floor depth; loads; and fire, vibration and acoustic ratings. Composite floor systems optimize the cost and performance of your mid-rise or high-rise project and can weigh up to 40% less than comparably utilized
Bridge deck stay-in-place forms For new construction and rehabilitation of concrete or steel bridge structures, we offer two steel stay-in-place bridge deck forming systems. • Bridge-Dek®: High-strength galvanized steel with factoryclosed ends that speed installation, creates a safe working platform, reduces costs 20% to 25% compared to wood forms, and integrates with steel or concrete girders. • Rhino-Dek®: Polymer laminated for corrosive environments—available on one or both sides of the deck pan—protects exposed steel from salt corrosion. Provides a service life of 124 years.
ADVERTORIAL
Steel joists and joist girders are key components of the most costeffective, performance-optimized structural steel solutions. All our steel joists and joist girders are engineered and manufactured in accordance with the specifications of the Steel Joist Institute. • Standard steel joists and joist girders: Primary and secondary framing members, steel joists and joist girders support concentrated loads for roof or floor systems. • Special profile joists: Profiles include gable, bowstring, arched, scissor and double-pitched joists. Over 40,000 special profile steel joist design possibilities. • Composite joists: Enable the longest open floor spans possible. Flush-frame connections are a versatile and efficient method for connecting open-web steel joists to wide flange girders. • WN-Series™ wood nailer joists: For stronger, moreefficient and better-performing wood-on-steel roof systems, our unique glued finger joint splices provide structural continuity the full length of the joist.
cast-in-place concrete floors. Long-span deck can be specified to minimize floor depth, optimize floorto-floor height, reduce project costs and accelerate construction timelines. Composite deck used in combination with composite joists can achieve clear spans up to 60 feet uninterrupted by support columns. Together with you, our team will help you find the ideal steel deck and deck finish for your project.
Resources for structural engineers To streamline the specification of steel joists and deck, we offer a range of informational and educational resources. • Load tables: Our downloadable load tables catalogs for steel joists and steel deck enable you to work quicker, not harder. • Online design tools: Interactive steel joist and steel deck design tools transform your design process, helping increase project performance and reduce project costs. • Credit-hour courses: Our continuing education courses are offered in three calendar-friendly formats: live remote, on-site and on-demand. Many courses award AIA and PDH credit. Courses can be customized or tailored to your interests and needs. You’ll learn from experienced steel specialists and advance your knowledge of structural steel.
Start building success together Solve engineering challenges. Realize project goals. Control costs. Your success begins with the selection of the right steel joists and deck—and the right supplier—for your application. At New Millennium, we will help you determine the optimal structural steel solution for your application. Together, let’s build it better.
newmill.com
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SEISMIC Dlubal Software, Inc.
ENERCALC, LLC
RISA Technologies
Phone: 267-702-2815 Email: info-us@dlubal.com Web: www.dlubal.com Product: RFEM 6 | RWIND 2 Description: Discover RFEM 6, the structural design software with a seismic response spectrum analysis per ASCE 7 and other international standards. Integrate with the CFD wind analysis program RWIND 2 to determine wind loads on even the most complex structures. Download a free 90-day trial at www.dlubal.com today!
Phone: 800-424-2252 Email: info@enercalc.com Web: https://enercalc.com Product: ENERCALC SEL / ENERCALC 3D Description: ENERCALC automatically incorporates seismic loads in load combinations, including the vertical component, redundancy & system overstrength factors, as applicable. ENERCALC supports ASCE 7’s Base Shear, Demands on Non-Structural Components & Wall Anchorage. ENERCALC also includes earth retention wall modules - including substantial segmental wall improvements, & ENERCALC 3D FEM.
Phone: 949-951-5815 Email: info@risa.com Web: risa.com Product: RISA-3D Description: Feeling overwhelmed with seismic design procedures? RISA-3D has you covered with seismic detailing features including full AISC-341/358 code checks. Whether you’re using RISA-3D’s automated seismic load generator, or using the builtin dynamic response spectra & time history analysis/ design capabilities, you’ll get designs and reports that meet all your needs.
DuraFuse Frames Phone: 801-727-4064 Email: contact@durafuseframes.com Web: www.durafuseframes.com Product: DuraFuse Frames Description: DuraFuse Frames® are the most economical and the most resilient prequalified steel moment connection. Seismic energy is dissipated by an easily replaceable fuse plate protecting the beam and column from damage in an earthquake, making the building easily repairable. Add resilience and reduce costs on your projects with DuraFuse Frames.
Not listed?
Monthly 2024 Resource Guide forms are now available on our website. STRUCTUREmag.org
STRUCTURAL ENGINEERING
Resource Guide
Profile
DURAFUSE FRAMES
A
DuraFuse connections are prequalified in AISC 358-22 and enjoy full compliance with performance requirements in AISC 341 with code approvals from IAPMO UES ER 610 including 2021 IBC, 2022 CBC, and 2023 LABC Supplements. Numerous Technical Bulletins provide additional resources related to performance, modeling, and design. Modeling, design, and detailing of DuraFuse Frames are available in RAM Structural Systems, Revit, SDS2, and Tekla. DuraFuse engineers are constantly improving the modeling, analysis, and design process to ensure efficient, high performance, and resilient design solutions with quick response times. We are happy to provide a resilient design alternative using DuraFuse Frames based on your specifications. If you want to distinguish your next steel moment frame design, we can help you improve economy and repairability which will add value for your clients.
801-727-4060 | contact@durafuseframes.com | durafuseframes.com 94 STRUCTURE magazine
ADVERTORIAL
dd resilience and reduce costs on your steel moment frame projects with DuraFuse Frames®. Seismic energy is dissipated through an innovative fuse plate which prevents beam and column damage. The bottom flange fuse plate and all-bolted erection minimizes post-earthquake repair duration and cost. Full-scale laboratory and shake table testing have confirmed the performance and repairability. DuraFuse solutions apply to both new construction and retrofit of existing buildings with benefits including: • Downtime and repair costs are reduced by up to 65% following a severe earthquake (i.e., improved functional recovery) • Lower frame weight than any other prequalified moment connection • Elimination of seismic lateral bracing (eliminates approximately 70% of beam braces) • Completely field-bolted connection eliminates field welding and associated inspection • Fewer parts, less fit-up and less connection weight compared to other proprietary moment connections • Complimentary design support from the DuraFuse engineering team
STRUCTURAL ENGINEERING
Resource Guide
Profile
SIMPSON STRONG-TIE
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Simpson Strong-Tie expands product innovations for structural steel.
years of leadership in structural engineering, a steadfast dedication to service, technical expertise, and long-standing customer relationships enable Simpson Strong-Tie to understand the operational dynamics of the construction industry. We use this knowledge to develop advanced solutions for structural steel. Our innovative products and technology help everyone – from fabricators and erectors to building owners, engineers, and contractors – maximize efficiency and resiliency at every stage of the building process.
New Yield-Link® Brace Connection Adds Resiliency to Structural Steel
Bolted Connections Eliminate Field Welding As a longtime partner to the construction industry, Simpson understands that building owners have a vested interest in completing projects quickly and optimizing building occupancy. At the same time, the demand for new construction continues to outpace the availability of skilled-trade workers, such as welders.
Simpson Strong-Tie has added yet another design innovation to a growing suite of products and solutions for structural steel construction. Introducing the Yield-Link® brace connection (YLBC).
With these factors in mind, the engineers at Simpson StrongTie designed the YLBC to be installed with bolts instead of field welding. In addition to simplifying design and detailing, bolted connections save time and effort during installation while reducing testing, inspection costs and overall project schedules.
Engineered For High Seismic And Wind Areas
ADVERTORIAL
The YLBC connects brace frames in structural steel buildings. With pre-designed, bolted connections, it simplifies design work and is easy to incorporate into new builds or retrofits. In fact, the YLBC is ready to detail as soon as the building frame is sized. Along with the Yield-Link® moment connection and Edge-Tie™ system for cladding connections, the Yield-Link brace connection gives fabricators, erectors, engineers, building owners and contractors a proven, efficient and more economical solution for structural steel.
Every structure needs sufficient strength to allow occupants to shelter in place during a natural disaster or similar event. However, buildings located in high seismic or wind areas also need to accommodate fast repair methods, so that they can be returned to service quickly. The YLBC helps to fulfill both of these design objectives. During a powerful earthquake or extreme high-wind event, such as a hurricane or tornado, the YLBC functions as a replaceable, yielding element that isolates damage while keeping the structural steel brace intact. In addition to protecting braces, which are costly and time-consuming to repair, the YLBC is simple and cost-effective to replace, if needed.
Expert Service, Software And Support The YLBC is readily available through our nationwide distribution network and backed by industry-leading technical and field support. We also provide a wide selection of Building Technology software solutions that help streamline design and detailing. With Simpson Strong-Tie as a partner in structural steel, builders have the innovative products, technology and service to maximize efficiency and resiliency at every stage of the engineering and construction process. To learn more about the Yield-Link® brace connection, visit strongtie.com/ylbc. Yield Link brace to beam connection.
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MASONRY ASDIP Structural Software Phone: 407-284-9202 Email: support@asdipsoft.com Web: www.asdipsoft.com Product: ASDIP CONCRETE Description: An advanced software for the design of multi-span continues beams, biaxial slender columns, concrete and CMU bearing walls, shear walls, one-way slabs and wall opening design, per the latest design codes. This software includes 5 intuitive modules that can substantially simplify time-consuming calculations for your concrete and masonry structural designs.
The Masonry Society Phone: 303-939-9700 Email: info@masonrysociety.org Web: masonrysociety.org Product: TMS 402/602 - 2022 Description: Building Code Requirements and Specification for Masonry Structures. Contains TMS 40222 (Building Code Requirements for Masonry Structures and TMS 602-22 Specification for Masonry Structures. Available in print, downloadable formats. Coming soon subscription based convenience with additional enhanced features. Watch the TMS website for announcements.
RISA Technologies Phone: 949-951-5815 Email: info@risa.com Web: risa.com Product: RISA-3D Description: Harness the power of finite element analysis for your masonry design. RISA-3D allows you to draw and load masonry walls, openings, and lintels. Code checks for both in and out of plane are provided, as well as rebar optimization. Design includes the TMS 402-16 masonry code, both ASD and Strength.
ENERCALC, LLC Phone: 800-424-2252 Email: info@enercalc.com Web: https://enercalc.com Product: ENERCALC SEL / ENERCALC 3D Description: Whether it’s masonry slender walls, masonry beams and lintels, or masonry cantilevered retaining wall stems, ENERCALC has the solution. The masonry design modules feature flexible geometry definition, thorough load combinations, and clear concise output. Instant recalculation allows you to easily “what-if” your designs. Check out ENERCALC’s masonry design capabilities today!
Hohmann & Barnard, Inc. Phone: 800-645-0616 Email: jenniferm@h-b.com Web: www.h-b.com Product: 2-SEALTM Thermal Wing Nut AnchorDescription: Hohmann & Barnard’s 2-SEALTM Thermal Wing Nut Anchor is an innovative, single screw veneer tie for metal stud construction. It features a dualdiameter barrel with factory-installed EPDM washers to seal both the face of the insulation and the air/vapor barrier, and unique Thermal Wings designed to decrease thermal transfer through rigid insulation. Product: ENVIRO-BARRIERTM SILICONE SYSTEM Description: Hohmann & Barnard offers a premium silicone air- and water-resistive barrier (AWB)? ENVIROBARRIERTM SILICONE is a 100% silicone coating that is solvent-free and fluid-applied. Primerless adhesion means no bonding agent! The elastomeric membrane bonds to most construction materials, including exterior gypsum board, CMU, concrete, stone, wood and metal.
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STRUCTURAL ENGINEERS 30,000 via PRINT
25,000 via EMAIL 80,000 via WEBSITE
PROSOCO Phone: 800-255-4255 Email: customercare@prosoco.com Web: PROSOCO.com Product: Grip-Ties Description: PROSOCO’s high-strength mechanical anchors fortify and stabilize existing brick facades against external forces. Grip-Ties are an excellent solution to reanchor a masonry or stone facade to metal or wood studs, structural steel, tile, block, concrete or brick. Product: Grout-Ties Description: The Grout-Tie improves the stability of masonry walls by filling in voids while minimizing disruption. This cost-effective method can pin rubble-filled masonry or stone walls, re-connect veneer walls to the backup structure, and pin masonry arches. This easy process installs the grout and tie simultaneously.
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STRUCTURAL ENGINEERING
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HOHMANN & BARNARD
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Innovating Masonry for Over 90 Years
Our 2-SEAL™ Thermal Wing Nut Anchor has a single-screw veneer tie for metal stud construction, with thermal wings made from steel encapsulated in flame-resistant plastic to create a thermal break. EPDM washers seal at both the face of the insulation and the air/vapor barrier. The anchor spins to easily orient pintles/hooks parallel to masonry joints. The HB RS FLEXbracket Rainscreen Support Bracket is a stainless steel universal bracket that is ordered to fit the depth of insulation needed on a project. The bracket accepts various aluminum rail systems and can be installed for both vertical and horizontal rails. Other features include: • Thermal shims can be added for increased energy efficiency • Reduces thermal transfer • Dual friction fingers for ease of installation • Adjustable engineered system With our Concealed Lintels, you can build beauty into your next project! Create a distinguished look using any of our three arch options: Surfaced Mounted Arch, Flat Spine or Arch Spine. A full set of drawings and calculations, all necessary components, and support from H&B’s Engineering Team make the installation of our Concealed Lintels easy and stress-free. If you can dream it, we can customize the look of your building. The result is an instant upgrade that adds unique character and unmatched opulence to your project. Our Repair and Restoration Anchors play a role in the preservation of many beautiful, historical buildings and landmarks. Our Torq-Lok® Mechanical Anchoring System is an easy-to-use and cost-effective method to re-connect existing veneers to various substrates. The Panel-Lok® Panel Re-anchoring System is a mechanically activated, economical way to re-anchor existing stone panel veneers to concrete, solid and/or hollow masonry, and steel substrates. These processes eliminate the need to tear down an existing veneer or remove existing stone through the provision of a corrosion-resistant tie assembly. H&B’s ENVIRO-BARRIER™ SILICONE System helps your wall resist air leakage and water penetration. This air and water-resistive barrier (AWB) has a 100% silicone coating that is solvent-free, fluidapplied, and used to coat and seal above-grade wall assemblies. Primerless adhesion means no bonding agent! The elastomeric membrane bonds to most construction materials, including exterior gypsum board, CMU, concrete, stone, wood and metal. Our ENVIRO-BARRIER™ VP is a single-component, fluid-applied, elastomeric membrane that provides an air and water barrier when applied to above-grade wall assemblies. Through the combined benefits and features of ENVIRO-BARRIER™ SILICONE AWB, ENVIROBARRIER™ LIQUID-FLASH™ SILICONE flashing, EB SILICONE TS transition strip, and EB REINFORCING FABRIC, H&B can to provide resistance to air leakage and water penetration. ENVIROBARRIER SILICONE has added benefits of UV resistance with a simple, single-coat application. Let Hohmann & Barnard help you engineer a complete wall system to ensure the full integrity of your next masonry project!
ADVERTORIAL
or more than 90 years, Hohmann & Barnard, Inc., has delivered innovative solutions for the masonry industry. We are a global leader in manufacturing construction materials for the building envelope. We offer anchors and reinforcement, moisture protection, restoration anchors, thermally efficient systems, air/vapor barrier systems, rainscreen support systems, and custom-engineered solutions for the mason contractor. Among the products we provide to both commercial and residential markets are our unmatched thermal performance products. Our groundbreaking Thermal Brick Support (TBS) System reduces thermal bridging in shelf angles to improve the energy efficiency of your building. The innovative bracket system features job-specific engineering to move the shelf angle away from the wall. This allows for continuous insulation behind the shelf angle, further increasing energy efficiency and reducing labor costs. Our new thermal Rainscreen Support Systems can increase thermal efficiency on your next cladding project. Our HB RS EZclad Rainscreen Support System is fully engineered to project conditions by H&B’s team of engineers. The system uses stainless steel structural connecting components, reducing conductivity and increasing thermal efficiency. Additional benefits include: • Allows for inward and outward adjustability • Does not interrupt continuous insulation • Thermal shims can be added for more thermal efficiency • Can be powder coated or anodized for aesthetics • Includes structural connection, rail, engineering calculations, and shop drawings
800-645-0616 | h-b.com
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WOOD ASDIP Structural Software Phone: 407-284-9202 Email: support@asdipsoft.com Web: www.asdipsoft.com Product: ASDIP WOOD Description: Our newest software for the design of wood members such as biaxial columns, continuous beams, and out-of-plane bearing walls based on the latest NDS provisions for ASD and LRFD design methods. Easily select Sawn lumber, Glued Laminated, or Composite Lumber sections. Graphic display of 2D and 3D interaction diagrams.
Cast Connex Phone: 888-681-8786 Email: info@castconnex.com Web: http://www.castconnex.com/ Product: Timber End Connectors Description: Clevis-type fittings designed to connect to the ends of heavy timber or glue-laminated structural elements loaded in predominately tension or compression for use in architecturally exposed applications. Visit our website to view the TEC and our custom cast steel connectors for timber projects.
Dlubal Software, Inc.
RISA Technologies
Phone: 267-702-2815 Email: info-us@dlubal.com Web: www.dlubal.com Product: RFEM 6 Description: Explore RFEM 6, the ultimate software for mass timber projects! Utilize the North American CLT database, design CLT and timber members per NDS and other international standards, and seamlessly integrate with steel or concrete for hybrid structures. Get your free 90-day trial at www.dlubal.com today.
Phone: 949-951-5815 Email: benf@risa.com Web: risa.com Product: RISA-3D & RISAFloor Description: RISAFloor and RISA-3D form the premiere software package for wood design. Create 3D models of your entire structure and get complete design of wood walls, flexible diaphragms, dimensional lumber, glulams, parallams, LVL’s and joists. Custom databases for species, design of strap and hold-downs as well as panel nailing offer flexibility.
ENERCALC, LLC
Trimble
Phone: 800-424-2252 Email: info@enercalc.com Web: https://enercalc.com Product: ENERCALC SEL / ENERCALC 3D Description: Deadlines getting to you? Whether working with wood beams, trusses, columns, ledgers or shear walls, ENERCALC SEL saves hours of design time weekly. Built-in databases for sawn lumber and engineered wood products (VersaLam, Glu-Lam etc) put section properties and allowable stresses at your fingertips. Budget-friendly all-inclusive subscriptions make it easy.
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Phone: 678-737-7379 Email: jodi.hendrixson@trimble.com Web: http://www.tekla.com/us Product: Tekla Structures Description: Can be used for wood framing: True BIM model of wood framing, parametric components allow for easy creation and design change, easily add or move doors and windows, clash checking functionality to eliminate change orders, easily customizable to suit any job requirements.
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STRONGWELL CORP.
Benefits of FRP vs. Traditional Structural Materials
in thermal break applications. FRP is transparent to radio waves, microwaves, and other electromagnetic frequencies. Strongwell composite products are regularly used in cellular applications due to this feature, such as rooftop screening, enclosures, and support structures. FRP products offer excellent fire properties, based on the resin system used. Most Strongwell FRP is slow to ignite and selfextinguishing once the flame source is removed. FRP products will not leach any undesirable contaminants into water, soil, or air, making it suitable for water, ground, and animal contact without any special treatments or coatings.
FRP has a higher strength-to-weight ratio than most other materials, making it an ideal material when weight is a concern, weighing approximately 75% less than steel and 30% less than aluminum. This translates to lower transportation costs and easier and quicker installation with less Markets Served specialized labor and no hot works permits. Unlike metals, FRP will not The benefits of FRP make it ideal for applications in numerous markets permanently deform under load. including architectural, industrial, water/wastewater, cellular, coastal/ FRP is corrosion resistant, which means it won’t rust, rot, or corrode, marine, data centers, electric utility, infrastructure, mining, oil & gas, virtually eliminating any need for routine repair. This significantly reduces parks & recreation, waterparks, and transportation. life cycle costs. The polymer resin infused in the parts can also be optimized to accommodate environments with various corrosive chemicals. Learning More About Strongwell FRP FRP is low in electrical conductivity, making it a safer choice for Strongwell’s website is an invaluable resource for designers and engineers, as applications near power transmission or distribution. FRP is also low it offers design guides, specifications, CAD blocks, case studies, corrosion in thermal conductivity, making it a good insulator, which is valuable resistance information, brochures, fabrication worksheets, and much more. 276-645-8000 | info@strongwell.com | www.strongwell.com 98 STRUCTURE magazine
ADVERTORIAL
trongwell is the recognized world leader in the manufacture of fiber reinforced polymer (FRP) composites utilizing the pultrusion process. Pultrusion is a continuous production process which creates structural composite parts with a constant cross-section. Since its first pultrusion in 1956, Strongwell has developed hundreds of FRP structural shapes, plate, gratings, planking, railing, fencing, structural building panels, and much more, made in the USA in one of Strongwell’s three U.S. ISO 9001 certified facilities.
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WOODWORKS® SOFTWARE Design wood structures effectively, economically and with ease!
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automatically selecting the most economical sheathing and nailing patterns. The program also checks the inter-storey drift limits and implements provisions for structural irregularities from ASCE 7.
WoodWorks® Sizer
WoodWorks® Connections
The WoodWorks® Sizer is our most used software program. It enables designers to design beams, joists, columns, wall studs and panels used in light-frame construction as well as heavy and mass-timber construction. Sawn lumber, sawn timber, glulam, structural composite lumber, I-joists and CLT panels are available. The program analyzes all load combinations from ASD or LRFD as per IBC and ASCE 7 and designs for structural and fire resistances.
The WoodWorks® Connections program enables the designer to design connections consisting of bolts, lag screws, nails, wood screws, shear plates, rivets, and heavy steel hangers. The program includes different types of connections such as wood-to-wood, steel-to-wood, and wood-to-concrete. The results are displayed as fully dimensioned CAD quality drawings. Visit our website at woodworks-software.com to download a free trial, watch our training videos, or to access our step-by-step tutorials.
WoodWorks® Shearwalls The WoodWorks® Shearwalls is our most time saving program as it allows engineers to model the lateral force-resisting system of a light-frame wood building up to 6 stories either using an AutoCAD exported file as a template or by drawing from scratch. The software will automatically generate wind and seismic forces, distribute the forces to each level, within each level to each shearline based on flexible and rigid diaphragm analyses, and within each shearline to each shear wall segment based on wall stiffness or capacity. It designs full-height, force-transfer and perforated shear walls, and optimizes for sheathing and nailing by iterating and
800-844-1275 | sales@woodworks-software.com | www.woodworks-software.com
ADVERTORIAL
stablished decades ago, WoodWorks® Sizer, Shearwalls, and Connections programs are positioned as high-value, low-cost software with several thousand loyal customers in the U.S. and Canada. WoodWorks® is widely recognized as highly reputable since development of both the Canadian and U.S. versions are led by the Canadian Wood Council (CWC) and endorsed by American Wood Council (AWC) (U.S. version). For the U.S. version, we work closely with AWC to ensure consistency in technical interpretations of design provisions in the IBC, NDS, SDPWS, and ASCE 7. Both AWC and CWC participate in codes and standards development, and therefore have the necessary background to ensure the software operates as the codes and standards intend. WoodWorks® software programs provide designers with a quick and accurate way to design and optimize wood structural members, connections and light-frame shear walls.
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