Displacement Based Design Of Wall-Frame and Shear Wall Buildings

Abstract

The traditional Force Based Design (FBD) given in Seismic code uses empirical ap- proach without giving due consideration to the displacements which are actually responsible for the damage. After the yield point, the strength has least role to play, whereas the failure will take place at an ultimate displacement depending upon the level of ductility present in the structure. Therefore, it seems rational to carry out a seismic design wherein displacements are considered at the start of the design process. In order to prevent collapse in a major earthquake, the ductility demand on the struc- tural elements and the overall deformation of the structure needs to be controlled. It is suggested in various research articles that this can be achieved more rationally with Displacement Based Design (DBD) rather than FBD. In the present study, traditional FBD approach given in IS 1893 (Part 1) : 2002 is reviewed and its limitations are discussed. DBD is firstly implemented to single storey building modeled as Single Degree of Freedom (SDOF) system. Comparison among FBD and DBD of single storey building shows that later provides double the base shear, higher time period, lower stiffness and ductility. Later on, DBD is imple- mented to two buildings with different structural systems, namely, Wall-Frame and Shear Wall. Shear wall building is analyzed using DBD. Like in the case of SDOF system, DBD provides higher baser shear as compared to FBD, however, ductility reduces substantially. A parametric study is carried for shear wall building with re- spect to the height of the building. Similarly, Wall-Frame building is analyzed and base shear contribution of Wall and Frame is derived. It is designed using DBD and found that Time period, Damping and Base Shear of the building is higher as compared to FBD, however ductility is lower. A parametric study with respect to base shear contribution of wall and frame is carried out. Apart, Inelastic Design spectrum is developed from design spectrum given in IS 1893 (Part 1) : 2002. A four Storey Reinforced Concrete Frame building is considered to implement DBD using Inelastic Design Spectrum. It is found that the Response reduction factor for Inelastic spectrum comes out to be low as compared to Elastic spectrum for FBD.