Evaluation of Seismic Shear Demands of RC Core Walls in Thailand Determined by RSA Procedure

Abstract

ASCE 7 allows structural engineers to use Response Spectrum Analysis (RSA) procedure to compute the seismic design forces of the structures. However, seismic shear demands of reinforced concrete (RC) walls determined by RSA have been found to be inadequate by many researchers. This paper aims to investigate the seismic shear demands of RC core walls from low-rise to high-rise buildings. RC split core walls in five buildings varying from 5 to 25 stories subjected to earthquake ground motions in Bangkok and Chiang Mai of Thailand were first designed by RSA procedure in ASCE 7-10. Then nonlinear response history analysis (NLRHA) was conducted to compute more accurate seismic demands of the structures. The results demonstrated that shear demands of core walls from NLRHA were significantly larger than those from RSA procedure. The shear amplifications of core walls in cantilever-wall direction were larger than those in coupled-wall direction. The two building locations having different spectrum shapes led to different shear amplifications. Hence, an empirical formula cannot be applied to every location. In Bangkok, it is found that Rejec et al. (2012)’s equation could well estimate shear forces in cantilever direction of core walls but it significantly overestimated shear forces in coupled direction of core walls. In Chiang Mai, Luu et al. (2014)’s equation provided good estimation of shear forces in both directions of core walls. Beside these two equations, the shear magnification factor equation in EC8 is found acceptable to be adopted to multiply with shear force from RSA procedure before using it as design shear force of RC core wall in both Bangkok and Chiang Mai.