Use of Conditional Mean Spectra for Seismic Evaluation of RC Building Considering Soil Effects
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RESEARCH PAPER
Use of Conditional Mean Spectra for Seismic Evaluation of RC Building Considering Soil Effects Vishal R. Deoda1 • Shrabony Adhikary1 Received: 6 January 2020 / Revised: 12 May 2020 / Accepted: 8 June 2020 Ó Iran University of Science and Technology 2020
Abstract 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. Keywords CMS Soil–structure interaction Soil effects NLTHA
1 Introduction During an earthquake, the damage to any structure depends not only on the behaviour of super-structure but also on the sub-structure and local soil condition. The effects of soil (viz. soil–structure interaction (SSI) and soil amplification) play an important role in the seismic design of structures. A lot of research is done on the response of structure by considering SSI only [1–5], and limited work is available on the incorporation of both SSI and soil amplification simultaneously [6–9]. The SSI has two components, viz. inertial interaction and kinematic interaction. Out of them, the kinematic interaction has insignificant effect on longperiod structures and is mainly prominent for short-period & Shrabony Adhikary [email protected]; [email protected] Vishal R. Deoda [email protected]; [email protected] 1
Department of Civil Engineering, Visvesvaraya National Institute of Technology, Nagpur, India
structures [10–12]. One of the important effects of inertial interaction is soil–foundation flexibility, which reduces the total stiffness of the structure, thereby increasing the fundamental structural period and total displacement [3–5]. Therefore, the common practice of neglecting SSI effect is not always beneficial, particularly in the case when the displacement is governing design criteria
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