use of conditional mean spectra for seismic evaluation of rc building considering soil effects

Recently, the conditional mean spectrum (cms) has become an important tool in ground-motion selection for seismic evaluation of structures. in the present numerical study, a 10-storey rc frame building is assumed to be situated on type-ii soil and located in seismic zone v of india. the building is designed using the response spectrum analysis method of the indian seismic code. further, it is analysed using the nonlinear time history analysis method for three different cms ground motions. the numerical study is performed for three cases: (1) fixed base with actual earthquake record; (2) fixed base with site-specific earthquake record considering soil amplification; and (3) flexible base considering soil–foundation flexibility and soil amplification. the results of the analysis are compared for the above-mentioned cases in terms of lateral displacement and storey drifts. it is observed that the displacement profile of the structure subjected to all the three considered ground motions is not the same, although they are matching to cms. it is concluded that out of the two important soil effects, i.e. soil amplification and soil–foundation flexibility, soil amplification has a significant effect on the seismic response; however, the nature of response depends mainly on the ground-motion characteristics.