Estimating seismic demands of singly symmetric buildings by spectrum-based pushover analysis

Abstract

Buildings with the singly symmetric plan are more vulnerable to earthquake actions than the buildings with a symmetric-plan arrangement since the torsional effect caused by the asymmetricity will induce higher seismic demand and may cause unexpected damage to the buildings. Thus, it is a crucial challenge for researchers and engineers to predict seismic demands of asymmetric-plan buildings for the possible strengthening and retrofitting. Although some pushover-based analysis methods have been proposed for the fast prediction of asymmetric-plan buildings, most of them do not reasonably consider the dynamic coupling of vibration modes. This paper expands the spectrum-based pushover analysis (SPA) procedure, which is proved to be effective in predicting seismic demands of buildings with symmetric building plans, to three-dimensional structure systems, to estimate the seismic demands of singly symmetric structures. A comprehensive case study, which includes six frame buildings with different structural heights and mass eccentricity ratios under various levels of the input motions, was conducted to investigate the feasibility of the SPA method in estimating the seismic demands of one-way asymmetric-plan buildings. It is found from the comparison of seismic demands computed from the SPA method, the nonlinear response time history analysis, the consecutive modal pushover analysis and the modal pushover analysis that the SPA method is capable of predicting the seismic demands very well, in particular, the demands on the heavy side of the structure, where the seismic demand and damage are more significant.