Identification of Reasons for High Inelastic Seismic Demands in High Rise RC Core Wall Buildings

Abstract

Recently, the issue of high inelastic seismic demands at severe ground shakings such as MCE level has been highlighted in the conventionally designed high rise reinforced concrete (RC) core wall buildings. Furthermore, it is also found that the MCE level demands obtained from more rigorous non-linear response history analysis (NLRHA) are much greater than the DBE level demands obtained from the response spectrum (RS) procedure. In this study, different factors responsible for the high inelastic seismic demands and large difference between the demands obtained from the RS method and NLRHA are identified. A case study building is analyzed by the RS and NLRHA procedures using DBE response spectrum and the seven MCE spectrum compatible ground motions respectively. The factors which could be apparently responsible for large difference between the demands by the RS and NLRHA method are identified as: overstrength factor, excitation intensities, and different damping ratios. The effect of these factors on seismic demands is quantitatively estimated by performing the NLRHAs at different combination of damping ratios and excitation levels. Apart from three obvious factors, some other factors, which cannot be explained by the NLRHA, are also found to be responsible for the high inelastic seismic demands and large difference between the DBE demands by the RS procedure and MCE demands by the NLRHA procedure. To identify those factors, modal decomposition of the inelastic responses of the case study building using uncoupled modal response history analysis (UMRHA) is in progress.