Prediction of inelastic response of base-isolated building frame by pushover analysis

Abstract

With the advancements in the analysis tools to estimate the inelastic performance of the buildings, the Pushover Analysis (POA) has been adopted as a reliable procedure for the assessment of the nonlinear performance of the buildings. The pushover analysis has a few advantages over the nonlinear dynamic analysis; (i) it is less time-consuming; (ii) it is easy to implement as it does not require to define specific earthquake time-history data. The one of the governing parameters in the seismic response prediction by the POA is the choice of the load pattern. The present study is performed to evaluate the predictions of a new lateral load pattern (LLP) which is developed to perform the pushover analysis of base-isolated buildings. A LLP is developed by modifying the original uniform load pattern; as an example, a 5-storey building frame, which resembles low rise buildings and a 10-storey building, which resembles midrise buildings are selected for the analysis. The buildings are provided with the base isolation layer at the bottom of the buildings with the lead rubber bearings’ isolators (LRB). The POA is conducted by selecting three target displacements depicting three behavioral states of the building. The three states are such chosen to depict the structural behavior from elastic to plastic range. For the comparison purpose, the conventional LLP which corresponds to the fundamental mode shape is also used. The predictions of the newly proposed LLP are then compared with the accurate results obtained by conducting the Nonlinear Time History Analysis (NTHA). A suite of real far-field earthquake records is used for performing the NTHA. The study concludes that the new LLP provides better results as compared to the conventional LLP when compared to the benchmark estimates obtained by the NTHA.