Author : Sourabh Kriplani 1
Date of Publication :9th March 2017
Abstract: Contemporary seismic design procedure proposed in various national codes follow the force-based design approach. Force based method holds good for building behavior in elastic domain, whereas the precise inelastic behavior of same building during severe seismic event is unpredictable. Some performance assessment guidelines like FEMA 445 provide cumbersome iterative procedure to ascertain the seismic performance of buildings. The iterative procedure of FEMA 445 is difficult to be performed in design offices for regular buildings. Therefore, a design methodology based on anticipated nonlinear performance is desired. Moreover, the design method should be robust and shall involve few or no design revisions. Relative displacement or drift of different levels of building under seismic event is one of the primary reasons of structural damage. Structural damage can be evaluated on the basis of cracking or deformations or in terms of dimensional changes i.e. strains. Indirectly by controlling displacement/drift of structure, damage can be controlled. Therefore, a relatively new technique of performance based seismic design i.e. Direct Displacement Based Design (DDBD) has evolved in last two decades. The approach of Direct Displacement Based Design method (DDBD) proposed by many researchers differ from each other in terms of effective viscous damping equation, displacement profiles and consideration of mode shapes. The study presents the variation in magnitude of seismic base shear and storey shear amongst various DDBD approaches and compares with the currently prescribed force based approach in Indian seismic code. The study also evaluates the advantages as well as disadvantages of these methods.
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