Rated Loads for Lattice- and Telescoping-Boom Cranes579
Working Ranges of Cranes583
TOWER CRANES 584
Classification584
Operation589
Tower Crane Selection597
Rated Loads for Tower Cranes599
RIGGING 602
Rigging Basics602
Slings605
SAFETY 606
Crane Accidents606
Safety Plans and Programs609
Zones of Responsibility610
Summary611
Problems612
Resources613
Website Resources614
CHAPTER 18
Piles and Pile-Driving Equipment
616
Introduction616
Glossary of Terms616
PILE TYPES 618
Classifications of Piles618
Timber Piles619
Concrete Piles621
Steel Piles627
Composite Piles628
Sheet Piles629
DRIVING PILES 634
The Resistance of Piles to Penetration634
Site Investigation and Test Pile Program635
Pile Hammers637
Supporting and Positioning Piles during Driving 647
Jetting Piles650
Spudding and Preaugering650
Hammer Selection651
Pile-Driving Safety653
Summary654
Problems655
Resources655
Website Resources656
CHAPTER 19
Air Compressors and Pumps657
Support Equipment657
COMPRESSED AIR 658
Introduction658
Glossary of Gas Law Terms658
Gas Laws660
Glossary of Air Compressor Terms661
Air Compressors662
Compressed-Air Distribution System665
Diversity Factor671
Safety672
EQUIPMENTFOR PUMPING WATER 674
Introduction674
Glossary of Pumping Terms674
Classification of Pumps675
Centrifugal Pumps676
Loss of Head Due to Friction in Pipe682
Rubber Hose683
Selecting a Pump684
Wellpoint Systems686
Deep Wells689
Summary689
Problems690
Resources692
Website Resources693
CHAPTER 20
Planning for Building
Construction694
Introduction694
Site Layout696
Delivery of Structural Components703
Steel Erection704
Tilt-Up Construction706
LIFTINGAND SUPPORT EQUIPMENT 710
Cranes710
Aerial Work Platforms714
Integrated Tool Carriers716
Telescopic Handlers/Forklifts718
Generators720
Welding Equipment722
CONTROLOF CONSTRUCTION NUISANCES 725
Construction Noise725
Noise Mitigation727
Lighting731
Dust731
Vibration732
Summary732
Problems733
Resources734
Website Resources735
CHAPTER 21
Forming Systems737
Classification737
Formwork and the Project Engineer739
Formwork Design741
Formwork Economics745
Vertical Systems752
Horizontal Systems760
Combined Vertical and Horizontal Systems 766
Shoring Towers771
Safety779
Summary780
Problems781
Resources782
Website Resources783
APPENDIX A
Alphabetical List of Units with Their SI Names and Conversion Factors 785
APPENDIX B
Selected English-to-SI Conversion Factors 787
APPENDIX C
Selected U.S. Customary (English) Unit Equivalents 788
APPENDIX D
Selected Metric Unit Equivalents 789 Index 790
PREFACE
The past decade has seen a shift in project delivery with owners seeking ways to accelerate project completion. Contractors have responded and are successfully delivering projects much more rapidly. A key element leading to successful execution of an acceleration effort is planning. Planning must include detailed analyses of equipment utilization. Additionally, there must be backup plans for all possible impediments. Speed is also achieved by working concurrent activities and opening multiple fronts, which means that a knowledge of equipment productivity is critically important to those wishing to compete in this new environment.
The use of design-build contracting is facilitating the introduction of innovation in design and construction. Further, the use of a new delivery approach, Construction Manager/General Contractor (CMGC), allows the owner to participate in the design phase while obtaining critical constructability input from the contractor. This CMGC approach provides for a cooperative relationship and also promotes innovation. Contractors striving to work in these new contracting environments are finding that equipment planning is now much more important.
Today, in the age of iPods, PDAs (personal digital assistant), laptop computers, the Internet, and the immediate download of data, there is an even greater need to plan equipment operations properly. A machine is economical only if used in the proper manner and in the environment in which it has the mechanical capabilities to function effectively. Technology improvements greatly enhance our ability to formulate equipment, planning, and construction decisions, but we must first have an understanding of machine capabilities and how to properly apply those capabilities to construction challenges.
To accelerate project work a contractor must develop its plans to a much greater level of detail due to schedule constraints and overall contracting risk. This eighth edition follows in the tradition of the first seven by providing the reader with fundamentals of machine selection and production estimating in a logical, simple, and concise format. With a grounding in
these fundamentals, the constructor is prepared to evaluate those reams of computer-generated data and to develop programs that speed the decision process or that enable easy analysis of multiple options.
Significant changes have been made to this edition. Cranes are used on both heavy civil and building projects for vertical movement of materials, yet there has been a shift in the culture of crane use. We have captured this change of perspective. The construction industry has seen a rash of crane accidents since publication of the seventh edition; therefore, greater emphasis has been placed on crane safety and lift planning.
Contracts for projects in urban environments are becoming more restrictive in terms of work schedule, vibration and noise, and any regulations that will limit work or logistic activities. Following a course plotted with the seventh edition, we have included more material about how to deal with such machine utilization issues and information concerning small machines used for building construction and urban projects in the “Planning for Building Construction” chapter.
Formwork systems are another component of accelerated construction. The “Forming Systems” chapter focuses on advanced modular and industrialized forming systems that can help realize faster project delivery.
The chapter on “Draglines and Clamshells” is now a part of the “Excavators” chapter so that all excavationtype activities are discussed in one chapter.
We have also found equipment manufacturers are continuing to place more machine specifications and operation materials on the Internet. Therefore, Web resource information is provided. In addition, Webbased exercises, which in some cases direct the student to specific machine information on the Web, have been added to some chapters. When you see the website icon in the text margin, visit our website at www.mhhe.com/peurifoy8e for additional resources and exercises available on the Web.
All chapters have undergone revision, ranging from simple clarification to major modifications, depending on the need to improve organization and presentation of concepts. Many photographs in the chapters have been updated to illustrate the latest equipment and methods, and more pictures of operating equipment have been used in this edition. Drawings have been added beside many of the figures so that the important features under consideration are clearly identified. Safety discussions are again presented in each of the chapters dealing with machine or formwork use.
The world of construction equipment is truly global, and we have tried to search globally for the latest ideas in machine application and technology. We have visited manufacturers and project sites in over two dozen countries around the world in gathering the information presented in this edition.
This book enjoys wide use as a practical reference by the profession and as a college textbook. The use of examples to reinforce the concepts through application has been continued. Based on professional practice, we have tried to present standard formats for analyzing production. Many companies use such formats to avoid errors when estimating production during the fastpaced efforts required for bid preparation.
To enhance the value of the book as a college textbook, we have changed problems at the close of each chapter. We have also included several problems that compel the student to learn using a step-by-step approach: these problems specifically request the solution for each step before moving on to reach a final solution. This approach focuses student learning by clearly defining the critical pieces of information necessary for problem solving. The solutions to some problems are included in the text at the end of the problem statements. Together with the examples, they facilitate learning and give students confidence that they can master the subjects presented.
We are deeply grateful to the many individuals and firms who have supplied information and illustrations. Four individuals are owed a particular debt of gratitude for their support and efforts. Prof. John Zaniewski, Director, Harley O. Staggers National Transportation Center, West Virginia University, has consistently provided assistance with the “Asphalt Mix Production and Placement” chapter, and for this edition we also depended on Mr. Jeff Williams, Vice President of Asphalt Plants for Payne and Dolan, Inc. in Waukesha,
Wisconsin. Mr. R. R. Walker of Tidewater Construction Corporation has consistently worked with us to improve the “Piles and Pile-Driving Equipment” chapter. Additionally, Prof. Amnon Katz from the Technion, Israel, has again helped with the “Concrete” chapter.
We would like to express our thanks for many useful comments and suggestions provided by the following reviewers:
Lauren Evans
Montana State University
Paul M. Goodrum
University of Kentucky
Jiong Hu
Texas State University–San Marcos
Victor Judnic
Lawrence Technological University–Michigan
Byung-Cheol Kim
Ohio University
Joel Lieberman
Phoenix College
Gene McGinnis
Christian Brothers University
Dustin Lee Olson
Brigham Young University
Aziz Saber
Louisiana Tech University
Steve Sanders
Clemson University
Scott Shuler
Colorado State University
Kenneth J. Tiss
SUNY College of Environmental Science and Forestry
However, we take full responsibility for the material. Finally, we wish to acknowledge the comments and suggestions for improvement received from persons using the book. We are all aware of how much our students help us to sharpen the subject presentation. Their questions and comments in the classroom have guided us in developing this revised book. For that and much more, we want to thank our students at the Air Force Academy, Arizona State University, Louisiana Tech, Purdue, Technion–Israel Institute of Technology, University of New Mexico, University of Wisconsin–Platteville, Virginia Tech, the Universidad de Piura, Universidad Technica Particuar de Loja, and the Universidad de Ricardo Palma, who have over the years
contributed so much helpful advice for clarifying the subject matter.
Most importantly we express our sincere appreciation and love for our wives, Judy, Reuma, and Lisa, who typed chapters, proofread too many manuscripts, kept us healthy, and who otherwise got pushed farther into the exciting world of construction than they probably really wanted. Without their support this text would not be a reality.
We solicit comments on the edition.
Cliff Schexnayder
Del E. Webb School of Construction Tempe, Arizona
Aviad Shapira Technion–Israel Institute of Technology Haifa, Israel
Robert Schmitt
University of Wisconsin–Platteville Platteville, Wisconsin
Cover photo: Construction of the Hoover Dam Bypass Composite Arch Bridge 880 feet over the Colorado River. It is the first hybrid arch bridge in the United States. The overall length is 1,900 feet, with an arch span of 1,060 feet. The concrete arch was cast of 10,000 psi concrete, the highest utilized in the United States. Completion of the bridge is scheduled for November 2010. Photo by C. J. Schexnayder
1 Machines Make It Possible
Construction is the final objective of a design, and the transformation of a design by construction into a useful structure is accomplished by men and machines. Men and machines transform a project plan into reality, and as machines evolve there is a continuing transformation of how projects are constructed. This book describes the fundamental concepts of machine utilization. It explains how to match machine capability to specific project requirements economically. The efforts of contractors and equipment manufacturers, daring to develop new ideas, constantly advance machine capabilities. As the array of useful equipment expands, the importance of careful planning for construction operations increases.
BEING COMPETITIVE
The past decade has seen a shift in project delivery, with owners seeking ways to accelerate project completion. Contractors have responded and are successfully delivering projects much more rapidly. A key element leading to successful execution of an acceleration effort is planning. Planning must include detailed analyses of equipment utilization. Additionally, backup plans must exist for all possible impediments. Speed is also achieved by working concurrent activities and opening multiple fronts, which means that a knowledge of equipment productivity is critically important to those wishing to compete in this new contracting environment.
The Yerba Buena Island (YBI) Viaduct carries Interstate 80 traffic across Yerba Buena Island and links the east spans of the San Francisco–Oakland Bay Bridge (SFOBB) with the YBI Tunnel. A 348-ft. portion of the YBI Viaduct was in need of replacement. It was decided to build a new structure next to the existing structure and then quickly demolish the old structure and move in the new structure. The SFOBB was closed to traffic at 8 P.M.on Friday night. Since there was no room to roll out the existing superstructure span,
the contractor chose to demolish the 6500-ton structure on-site within two days. The existing floor beams (75.5 ft. long each) were saw cut and hauled across the east span of the SFOBB to a dump site in Oakland. The substructure was demolished using demolition hammers. Lifting and moving the new span into place required slightly less than three hours. The clearance between the new and existing structure was 3 in. on each end. The superstructure was set on its new columns, and the column pins were installed. The column pins were dropped through prefabricated holes in the edge beam into prefabricated holes in the columns. The successful installation of the column pins was a testament to the tight tolerances the contractor was able to achieve during construction and moving. Traffic was placed back on the Bay Bridge at 6 P.M.Monday, 11 hours ahead of the scheduled 5 A.M.Tuesday opening. A video of the demolition and roll-in operation can be found on the McGraw-Hill website supporting this book. This project is a vivid example of what can be accomplished when a job is properly planned.
This book introduces the engineering fundamentals for machine planning, selection, and utilization. It helps you analyze operational problems and arrive at practical solutions for completing construction tasks. Its focus is the application of engineering fundamentals and analysis to construction activities and the economic comparison of machine choices.
The construction contractor’s ability to win contracts and to perform them at a profit is determined by two vital assets: people and equipment. To be economically competitive, a contractor’s equipment must be competitive, both mechanically and technologically. Old machines that require costly repairs cannot compete successfully with new equipment’s lower repair costs and higher production rates.
In most cases, a piece of equipment does not work as a stand-alone unit. Pieces of equipment work in groups. An excavator loads trucks that haul material to a location at the project where it is required. At that point, the material is dumped and a dozer spreads the material. After spreading, a roller compacts the material to the required density. Therefore, a group of machines—in this example an excavator, trucks, a dozer, and a roller—constitutes what is commonly referred to as an equipment spread.
Optimization in the management of an equipment spread is critical, both in achieving a competitive pricing position and in accumulating the corporate operating capital required to finance the expansion of project performance capability. This book describes the basic operational characteristics of the major heavy construction equipment types. More important, however, is that it explains the fundamental concepts of machine utilization, which economically match machine capability to specific project construction requirements.
There are no unique solutions to the problem of selecting a machine to work on a particular construction project. All machine selection problems are influenced by external environmental conditions. The noise and vibrations caused by construction operations and machines impact those adjacent to the project. Nearby residents complain about noise and glare from temporary light-
ing systems, and city codes restrict operations. Therefore, it must be understood that selecting a machine for a project involves an understanding of the environment in terms of soil type and moisture conditions—the physical environment of the work site—and also in terms of the surrounding environment impacted by the construction operations.
THE HISTORY OF CONSTRUCTION EQUIPMENT
Machines are mechanical/electrical systems that amplify human energy, improve our level of control, and process information. They are a vital resource necessary for the accomplishment of most construction projects (see Figure 1.1). One of the most obvious problems in constructing a project is how to transport heavy building materials. Machines provide the solution to that problem. The proof of how well the planner understands the work that must be accomplished and selects appropriate machines for that purpose is revealed by counting the money when the contract is completed. Did the company make a profit or sustain a loss?
From the time the first man decided to build a simple structure for protection from the elements through to the construction of the Egyptian pyramids, the Great Wall of China, the Inca monuments at Machu Picchu, and continuing until the mid-nineteenth century, work was accomplished by the muscle of
FIGURE 1.1 Modern hydraulic excavator on pneumatic tires
corvée
Labor required in lieu of taxes.
man and beast. When Ferdinand de Lesseps began excavating the Suez Canal in April 1859, corvée laborers, provided by the Egyptian viceroy, did the work of digging that trench in the desert.
Human labor assisted by only a very few machines continued the work on the canal for the next four years. But in 1864, Lesseps and his engineers began experimenting with machines, and eventually 300 steam-powered mechanical dredges were at work. Those machines, in the final three years of the project, excavated the majority of the main canal’s 74 million cubic meters. Mechanization—machines—transformed the project and continues to transform how projects are built today.
The Dreams
The development of construction equipment followed major changes in transportation modes. Where travel and commerce took place via water systems, builders dreamed of machines that would aid in dredging ports, rivers, and canals. As early as 1420, the Venetian Giovanni Fontana was dreaming of and diagramming dredging machines. Leonardo da Vinci designed such a machine in 1503, and at least one of his machines was actually built, but the power source was a lonely runner on a treadmill.
On July 4, 1817, at a site near Rome, New York, ground was broken for the 363-mile-long Erie Canal. It was excavated by the efforts of local laborers and Irish immigrants—human labor. However, by the 1830s, construction in the United States was changing from canal building to railroad construction. The Middlesex Canal, which connected Boston to the Merrimack River at Lowell, had been in service since 1803, but in 1835 the Boston & Lowell Railroad opened for service. Nevertheless, construction, be it building canals or railroads, was still achieved by the brawn of man and beast.
Steam Power Machines
William S. Otis, a civil engineer with the Philadelphia contracting firm of Carmichael & Fairbanks, built the first practical power shovel excavating machine in 1837 (Figure 1.2). The first “Yankee Geologist,” as his machines were called, was put to work in 1838 on a railroad project in Massachusetts. The May 10, 1838, issue of the Springfield Republican in Massachusetts reported, “Upon the road in the eastern part of this town, is a specimen of what the Irishmen call ‘digging by stame.’ For cutting through a sand hill, this steam digging machine must make a great saving of labor.”
Continued development of the steam shovel was driven by a demand for economical mass excavation machines. In the early 1880s, an era of major construction projects began. These projects demanded machines to excavate large quantities of earth and rock. In 1881, Ferdinand de Lessep’s French company began work on the Panama Canal. Less than a year earlier, on December 28, 1880, the Bucyrus Foundry and Manufacturing Company, of Bucyrus, Ohio, came into being. Bucyrus became a leading builder of steam shovels,
and 25 years later when the Americans took over the Panama Canal work, the Bucyrus Company was a major supplier of steam shovels for that effort.
Still, the most important driver in excavator development was the railroad. Between 1885 and 1897, approximately 70,000 miles of railway were constructed in the United States. William Otis developed his excavator machine because the construction company Carmichael & Fairbanks, for which he worked and in which his uncle Daniel Carmichael was a senior partner, was in the business of building railroads.
The Bucyrus Foundry and Manufacturing Company came into being because Dan P. Eells, a bank president in Cleveland, was associated with several railroads. In 1882, the Ohio Central Railroad gave the new company its first order for a steam shovel, and sales to other railroads soon followed.
Internal Combustion Engines
By 1890, courts of law in Europe had ruled that Nikolaus Otto’s patented fourcycle gasoline engine was too valuable an improvement to keep restricted. Following the removal of that legal restraint, many companies began experimenting with gasoline-engine–powered carriages. The Best Manufacturing Company (the predecessor to Caterpillar, Inc.) demonstrated a gasoline tractor in 1893.
The first application of the internal combustion engine for excavating equipment occurred in 1910 when the Monighan Machine Company of
1 “Steam Excavating Machine,” London Journal of Arts and Science, Vol. 22, 1843.
FIGURE 1.2 The Otis steam shovel; this machine was mounted on steel wheels that ran on rails.1
Chicago shipped a dragline powered by an Otto engine to the Mulgrew-Boyce Company of Dubuque, Iowa. Henry Harnischfeger brought out a gasolineengine–powered shovel in 1914. Following World War I, the diesel engine began to appear in excavators. A self-taught mechanic named C. L. “Clessie” Cummins, working out of an old cereal mill in Columbus, Indiana, developed the Cummins diesel engine in the early 1900s. The Cummins engine soon replaced the steam boiler in shovels. Warren A. Bechtel, who in 1898 entered the construction business in Oklahoma Territory and quickly built a reputation for successful railroad grading, pioneered the use of motorized trucks, tractors, and diesel-powered shovels in construction.
In the winter of 1922–1923, the first gas-powered shovel was brought into the state of Connecticut, and in the spring of 1923, it was employed on a federal-aid road project. The third phase of transportation construction had begun. Contractors needed equipment for road building. In 1919, Dwight D. Eisenhower, as a young army officer, took an Army convoy cross-country to experience the condition of the nation’s roads (see Figure 1.3). But as the country began to improve its road network, World War II intervened, and road building came to a near halt as the war unfolded.
FIGURE 1.3 Photograph with Eisenhower’s description of conditions
Courtesy Dwight D. Eisenhower Library
Incubators for Machine Innovation
Los Angeles Aqueduct Large construction projects provide a fertile testing ground for equipment innovation. William Mulholland, as Los Angeles city engineer, directed an army of 5000 men for five years constructing the Los Angeles Aqueduct, which stretches 238 miles from the Owens River to Los Angeles. In 1908, the Holt Manufacturing Company (the other predecessor to Caterpillar, Inc.) sold three gas-engine caterpillar tractors to the city of Los Angeles for use in constructing the aqueduct. In addition to crossing several mountain ranges, the aqueduct passed through the Mojave Desert, a severe test site for any machine. The desert and mountains served as the testing ground for the Holt machines, but Benjamin Holt viewed the entire project as an experiment and development exercise.
Holt found that cast-iron gears wore out quickly from sand abrasion, so he replaced them with gears made of steel. The brutal terrain broke suspension springs and burned up the two-speed transmissions in his tractors. The low gear was simply not low enough for climbing the mountains. Holt made modifications to the tractors both at his factory and in the desert. His shop manager, Russell Springer, set up repair facilities in the project work camps. After completion of the project, Mulholland in his final report labeled the Holt tractors as the only unsatisfactory purchase that had been made. But Holt had developed a much better machine because of the experience.
Boulder Dam In the years between the two world wars, one particular construction project stands out because of the equipment contributions that resulted from the undertaking. The Boulder Dam project (later named the Hoover Dam) was an enormous proving ground for construction equipment and techniques.
The use of bolted connections for joining machine pieces together came to an end in the Nevada desert as the project provided the testing ground for R. G. LeTourneau’s development of welded equipment and cable-operated attachments. LeTourneau, through his numerous innovations in tractor/scraper design, made possible the machines that later built airfields around the world during World War II. Other developments that came from the Boulder Dam project included sophisticated aggregate production plants, improvements in concrete preparation and placement, and the use of long-flight conveyor systems for material delivery.
Three Significant Developments
After World War II, road building surged, and in 1956 Eisenhower, now president, signed the legislation that established the Interstate Highway Program. To support the road-building effort, scrapers increased in capacity from 10 to 30 cubic yards (cy). With the development of the torque converter and the power shift transmission, the front-end loader began to displace the old “dipper” stick shovels. Concrete batch and mixing plants changed from slow,
torque converter
A fluid-type coupling that allows an engine to be somewhat independent of the transmission.
manually controlled contraptions to hydraulically operated and electronically controlled equipment. But the three most important developments were highstrength steels, nylon cord tires, and high-output diesel engines.
1. High-strength steels. Up to and through World War II, machine frames had been constructed with steels in the 30,000 to 35,000 psi yield range. After the war, steels in the 40,000 to 45,000 psi range with proportionally better fatigue properties were introduced. The new high-strength steel made possible the production of machines having a greatly reduced overall weight. The weight of a 40-ton off-highway truck body was reduced from 25,000 to 16,000 lbs, with no change in body reliability.
2. Nylon cord tires. The utilization of nylon cord material in tire structures made larger tires with increased load capacity and heat resistance a practical reality. Nylon permitted the actual number of plies to be reduced as much as 30% with the same effective carcass strength but with far less bulk or carcass thickness. This allowed tires to run cooler and achieve better traction, and it improved machine productivity.
3. High-output diesel engines. Manufacturers developed new ways to coax greater horsepower from a cubic inch of engine displacement. Compression ratios and engine speeds were raised, and the art of turbocharging was perfected, resulting in a 10 to 15% increase in flywheel horsepower.
Today, no radically new equipment appears on the horizon, but manufacturers are continually refining the inventions of the past, and the development of new attachments will mean improved utility for the contractor’s fleet. The future of equipment technology or innovation can be divided into three broad categories:
■ Level of control: equipment advancements that transfer operational control from the human to the machine.
■ Amplification of human energy: shift of energy requirements from the man to the machine.
■ Information processing: gathering and processing of information by the machine.
The Future
A time may come when the base machine is considered only a mobile counterweight with a hydraulic power plant. The base machine will perform a variety of tasks through multiple attachments. This trend has started with hydraulic excavators having many attachments, such as hammers, compactors, shears, and material-handling equipment. Wheel loaders, no longer standard bucket machines, have seen the introduction of the tool-carrier concept. Other attachments such as brooms, forks, and stingers are available so that a loader can perform a multitude of tasks. Other attachments will be developed, offering the contractor more versatility from a base investment.
Safety features and operator station improvements are evolving to compensate for today’s less experienced workforce. Related to workforce quality is the proliferation of supporting machine control technologies. Navigation of equipment is a broad topic, covering a large spectrum of different technologies and applications. It draws on some very ancient techniques as well as some of the most advanced in space science and engineering.
The new field of geospatial engineering is rapidly expanding, and a spectrum of technologies is being developed for the purposes of aeronautic navigation, mobile robot navigation, and geodesy. This technology is rapidly being transferred to construction applications (Figure 1.4).
The laser and global positioning system (GPS) guidance are becoming more common and reduce the need for surveyors to stake the work in the field. All the grader or dozer operator will need to do is load the digital terrain model into the onboard computer and then guide the machine where the display indicates. Machine position, along with cut or fill information, will appear on a screen in front of the operator at all times. This may turn the operator’s job into a video game of sorts.
Ultimately, operators sitting in a machine cab may be eliminated altogether. Caterpillar is developing and testing automated rock-hauling units for mining. These units are linked by radio to the office and tracked by GPS. The superintendent need only use a laptop to send the start signal and the trucks do the rest, leaving the lineup at set intervals and following the prescribed course. The superintendent can track the progress of each machine on the computer. If a truck develops a problem, the situation is signaled to the superintendent for corrective action.
GPS
A highly precise satellite-based navigation system.
FIGURE 1.4 Grader working with an automatic blade control
Further in the future, machine designers are thinking of an operator working from home. The field operations would be projected by large-scale display devices onto the walls of a room. The operator would operate the machine from these images enhanced by glasses that provide a 3D effect. Machine performance data would go directly to the machine maintenance contractor. Historical data and an electronic design file will guide the operator’s control activities. Machine work data will flow directly into the project schedule data file as work is accomplished.
THE CONSTRUCTION INDUSTRY
By the nature of the product, the construction contractor works under a unique set of production conditions that directly affect equipment management. Whereas most manufacturing companies have a permanent factory where raw materials flow in and finished products flow out in a repetitive, assembly-line process, a construction company carries its factory with it from job to job. At each new site, the company proceeds to set up and produce a one-of-a-kind project. If the construction work goes as planned, the job will be completed on time and with a profit.
Equipment-intensive projects present great financial risk. Many projects involving earthwork are bid on a unit-price basis, and large variations can exist between estimated and actual quantities. Some projects require an equipment commitment that is greater than the amount that a contractor will be paid for completing the work. Such a situation forces a contractor into a continuing sequence of jobs to support the long-term equipment payments.
Additional risk factors facing contractors in equipment-intensive work include financing structure, construction activity levels (the amount of work being put out for bid), labor legislation and agreements, and safety regulations. Project size and outdoor work that is weather-dependent contribute to long project durations. Projects requiring two or more years to complete are not uncommon in the industry.
Government-initiated actions that seriously affect the operating environment of the construction contractor are labor legislation and safety regulation. In each of these areas, many regulations impact a contractor’s operations. These actions can directly influence equipment decisions. Legislative acts that exert direct pressure on equipment questions include the Davis-Bacon Act, which is concerned with wage rates, and the Occupational Safety and Health Act (OSHA), which specifies workplace safety requirements. More than half of the dollar volume of work in the equipment-intensive fields of construction is subject to wage determinations under the Davis-Bacon Act, and this strongly influences the labor costs incurred by contractors. OSHA, by its rollover protective structures (ROPS) mandate, substantially increased the cost of those pieces of construction equipment that required that these structures be included as part of the basic machine. This particular regulation had a single-point-intime effect on equipment decisions, much like that resulting from the introduction of new equipment technology. Similarly, there remains the possibility of
additional safety requirements. Sound and emissions are issues that are receiving greater regulatory attention. Some owners, by clauses in the construction contract, are limiting machine noise levels.
Construction equipment to be certified includes any equipment of the types listed in Table XX brought on site.
This equipment must be retested every six months while in use on site. Any equipment used during construction may be subject to confirmatory noise level testing by the contractor at the request of the engineer.
SAFETY
The rate of personal injury and death resulting from construction work is too high. Of all major industry classifications, construction has one of the poorest safety records. The construction industry employs nearly 6.4 million people— about 6% of the American workforce. However, according to the National Safety Council, the industry has about 23% of the deaths and 10.3% of the injury accidents every year. That translates into 1150 to 2000 deaths and 400,000 disabling injuries annually. The Construction Industry Institute estimates the direct and indirect costs of construction accidents may be as high as $17 billion annually. The major causes of deaths and injuries are falls from elevations, electrocution, being struck by equipment, being caught in between equipment, and trench excavation cave-ins. As an industry, we are responsible and accountable for those statistics. It is the responsibility of construction managers to create the safety programs that will prevent accidents (Figures 1.5 and 1.6). We have both a moral and a business interest in doing so. The key is to provide the leadership, the programs, and the incentives to create a safe industry.
In the late 1960s, Congress began an investigation of construction safety, and in 1970, it enacted the Williams-Steiger Act, more commonly referred to as the Occupational Safety and Health Act. The act provided a comprehensive set of safety rules and regulations, inspection procedures, and safety recordkeeping requirements. It imposed nationwide safety standards on the construction industry. It also permitted the states to enact their own OSHA legislation as long as the state legislation is at least as stringent as the federal legislation. Employers are required to provide their employees a safe place to work and to maintain extensive safety records.
The act also established the Occupational Safety and Health Administration (OSHA), with regional offices in cities throughout the country. OSHA is responsible for the administration of the legislation and the development of rules and regulations to implement the act. The OSHA rules and regulations are published in the Federal Register.OSHA Safety and Health Standards, Code of Federal Regulations, Title 29, Part 1910, contains the safety features that must be included in construction projects by the architect or engineer.
FIGURE 1.5 Cranes will easily overturn when not operated properly.
FIGURE 1.6 Job site and shop area housecleaning and neatness is important for safety reasons.
Construction and Health Regulations, Code of Federal Regulations, Part 1926, pertains specifically to construction contractors and construction work. The act provides both civil and criminal penalties for violations of OSHA regulations. The civil penalty for failure to correct a violation is $7000 per day with a maximum penalty of $70,000. Criminal penalties can include both fines and imprisonment. It is OSHA’s intent to establish a uniform set of safety standards that apply to construction and to enforce those standards actively. Contractors must maintain a current, up-to-date file of OSHA regulations and work proactively to comply with OSHA requirements.
THE CONTRACTING ENVIRONMENT
Construction contractors work within a unique market situation. The job plans and specifications that are supplied by the client dictate the sales conditions and product, but not the price. Almost all work in the equipment-intensive fields of construction is awarded on a bid basis, through either open or selective tender procedures. Under the design-bid-build method of contracting, the contractor states a price after estimating the cost based on a completed design supplied by the owner. The offered price includes overhead, project risk contingency, and the desired profit.
There is movement toward more design-build contracts, where the contractor also has control of the project design. With a design-build project, the contractor must state a guaranteed price before the design is completed. This adds an additional element of risk, because estimating the quantities of materials required to complete the project becomes very subjective. But the advantage to the contractor is that the design can be matched in the most advantageous way to the contractor’s construction skills. In either case, it is tacitly assumed that the winning contractor has been able to underbid the competition because of a more efficient work plan, lower overhead costs, or a willingness to accept a lower profit.
Not infrequently, however, the range between the high and low bids is much greater than these factors would justify. A primary cause of variance in bids is a contractor’s inability to estimate costs accurately. The largest portion of estimating variance is probably not caused by the differences between past and future projects but by a lack of accurate cost records. Most contractors have cost-reporting systems, but in numerous cases the systems fail to allocate expenses to the proper sources and therefore cause false conclusions when used as the historical database for estimating future work.
A construction company owner will frequently use both contract volume and contract turnover to measure the strength of the firm. Contract volume refers to the total dollar value of awarded contracts that a firm has on its books (under contract) at any given time. Contract turnover measures the dollar value of work that a firm completes during a specific time interval. Contract volume is a guide to the magnitude of resources a firm has committed at any one time and to possible profit if the work is completed as estimated. But contract
volume fails to answer any timing questions. A contractor who, with the same contract volume as the competition, is able to achieve a more rapid project completion, and therefore a higher capital turnover rate while maintaining the revenue-to-expense ratio, will be able to increase the firm’s profits. Contractors who finish work ahead of schedule usually make money.
PLANNING EQUIPMENT UTILIZATION
Each piece of construction equipment is specifically designed by the manufacturer to perform certain mechanical operations. The task of the project planner/estimator or the engineer on the job is to match the right machine or combination of machines to the job at hand. Considering individual tasks, the quality of performance is measured by matching the equipment spread’s production against its cost. Production is work done; it can be the volume or weight of material moved, the number of pieces of material cut, the distance traveled, or any similar measurement of progress. To estimate the equipment component of project cost, the planner/estimator must first determine machine productivity, which is governed by engineering fundamentals and management ability. Chapter 5 covers the principal engineering fundamentals that control machine productivity. Each level of productivity has a corresponding cost associated with the effort expended. The expenses that a firm experiences through machine ownership and use and the method of analyzing such costs are presented in Chapter 2.
Although each major type of equipment has different operational characteristics, it is not always obvious which machine is best for a particular project task. After studying the plans and specifications, visiting the project site, and performing a quantity take-off, the planner must visualize how best to employ specific pieces of equipment to accomplish the work. Is it less expensive to make an excavation with scrapers or to top-load trucks with a dragline? Both methods will yield the required end result, but which is the most economical method of attack for the given project conditions?
To answer that question, the planner develops an initial plan for employment of the scrapers and then calculates their production rate and the subsequent cost. The same process is followed for the top-load operation. The type of equipment that has the lowest estimated total cost, including mobilization of the machines to the site, is selected for the job.
To perform these analyses, the planner must consider both machines’ capability and methods of employment. In developing suitable equipment employment techniques, the planner must have knowledge of the material quantities involved. This book does not cover quantity take-off per se, but that process is strongly influenced by the equipment and methods under consideration. If it is determined that different equipment and methods will be used as an excavation progresses, then it is necessary to divide the quantity take-off in a manner that is compatible with the proposed equipment utilization. The person performing the quantity take-off must calculate the quantities so that
groups of similar materials (dry earth, wet earth, rock) are easily accessed. It is not just a question of estimating the total quantity of rock or the total quantity of material to be excavated. All factors that affect equipment performance and choice of construction method must be considered in making the quantity takeoff, such as location of the water table, clay, or sand seams; site dimensions; depth of excavations; and compaction requirements.
The normal operating modes of the particular equipment types are discussed in Chapters 5, 7 to 19, and 21. That presentation should not blind the reader to other possible applications, however. The most successful construction companies are those that, for each individual project, carefully study all possible approaches to the construction process. These companies use project preplanning, risk identification, and risk quantification techniques in approaching their work. No two projects are exactly alike; therefore, it is important that the planner begins each new project with a completely open mind and reviews all possible options. Additionally, machines are constantly being improved and new equipment is being introduced.
Heavy equipment is usually classified or identified by one of two methods: functional identification or operational identification. A bulldozer, used to push a stockpile of material, could be identified as a support machine for an aggregate production plant, a grouping that could also include front-end loaders. The bulldozer could, however, be functionally classified as an excavator. In this book, combinations of functional and operational groupings are used. The basic purpose is to explain the critical performance characteristics of a particular piece of equipment and then to describe the most common applications for that machine.
The efforts of contractors and equipment manufacturers who dare to develop new ideas constantly push machine capabilities forward. As the array of useful equipment expands, the importance of careful planning and execution of construction operations increases. New machines enable greater economies. It is the job of the estimator and the field personnel to match equipment to project situations, and that is the central focus of this book.
SUMMARY
Civilizations are built by construction efforts. Every civilization had a construction industry that fostered its growth and quality of life. This chapter presented an abridged history of construction equipment, an overview of construction work, and the risks associated with bidding work. Machine production, the amount of earth moved or concrete placed, is only one element of the machine selection process. It is also necessary to know the cost associated with that production. The critical learning objective is
■ An understanding of how construction equipment and machines have been developed in response to the demands of the work to be undertaken.
This objective is the basis for the problems that follow.
