International Research Journal of Engineering and Technology (IRJET) Volume: 04 Issue: 02 | Feb -2017
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e-ISSN: 2395 -0056 p-ISSN: 2395-0072
A COMPARATIVE STUDY OF FORCE BASED DESIGN AND DIRECT DISPLACEMENT BASED DESIGN FOR RC DUAL-WALL FRAME STRUCTURE. Salehali M. Bhaisaheb1, Dr.Bimal A. Shah.2 1PG
Student, Applied Mechanics & Structural Engineering department, Faculty of Technology & Engineering The Maharaja Sayajirao university Of Baroda , Vadodara, Gujarat , India. 2Head & Associate Professor, Applied Mechanics and Structural Engineering Department, Faculty of Technology & Engineering, The M.S. University of Baroda, Vadodara, Gujarat, India ---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract – The Indian Code method for calculating seismic
damage and the shocks of heavy intensities without total collapse.
forces for Reinforced Concrete Building ie IS 1893:2002 is Force Based which has some drawbacks such as initial stiffness Characterization, variation in Response Reduction factor, calculation of time period is height dependent. The code cannot calculate force required for specified performance of building. These problems resulted in the need for an alternative design approach, which lead to the Performance Based Design (PBD). Direct Displacement Based Design (DDBD) method is based on PBD. the major aspects of the entire paper in the following prescribed sequence. . Design and analysis is done for reinforced frame buildings of 8, 12, 16 and 20 storey based on following codes IS 456:2000, IS 1893:2002 and the two design approaches are studied. Analysis and design is done using commercial software ETABS 2015. It has been found that the reinforced concrete frame buildings designed by DDBD method is economical than those designed with FBD method under similar conditions of modeling.
The inelastic effects are indirectly accounted for by using a Response reduction factor R, which is based on some form of the equal-displacement and equal-energy principles. In the code procedures, an explicit assessment of the anticipated performance of the structure is not done. In the force based codal method of design, the base shear is computed based on perceived seismic hazard level, importance of the building and the appropriate force reduction factor. Then this base shear is distributed over the height of building with some prescribed or estimated distribution pattern. Force Based Design (FBD) suffers from many problems such as the assumed stiffness of the different structural elements, inappropriate response reduction factor and calculation of time period. The emphasis is that; the structure should be able to resist design base shear. Force based design method cannot design structures for target design objectives under a specified hazard level There are some inherent flaws in Force Based Design ie the Strength and Stiffness are considered independent which is Incorrect, Time period Calculations according to code includes height and lateral dimensions, which gives very low time period, Force Reduction Factor shows wide discrepancy when compared to codes of other nations, To mitigate this flaws an alternative design philosophy named “Displacement-Based Design (DBD)” was first introduced by Qi and Moehle (1991), which included translational displacement, rotation, strain etc. in the basic design criteria and then Direct Displacement Based Design (DDBD) was proposed by M.J.N. Priestley (1993) [1]. The Direct Displacement Based Design (DDBD) is based on Performance Based Design (PBD). This philosophy is a very promising design tool that enables a designer to design a structure with predictable performance.
Key Words: Force Based Design, Direct Displacement Based design, Is 1893:2002, RC Dual Wall-Frame Structure , Shear-Wall. 1.INTRODUCTION The most detrimental effect of all on a building is arguably Earthquake force and still there is no accurate method to predict behaviour of the building during such event. Hence need arises for a design practice that can give assurance for specified performance of a building during earthquake. Code practices have been Force Based; the current code IS 1893:2002 also uses the same. The methodology used is that the individual components are so proportioned and designed that they can perform specific goal during earthquake ie the structure c a n sustain the shocks of low intensities without damage, the structure can sustain the shocks of moderate intensities without structural
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2 Direct Displacement Based Design. The design procedure known as Direct Displacement-Based Design (DDBD) has been developed over the past ten years
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