Pushover analysis for estimating seismic demand of elliptic braced moment resisting frames

Abstract

In this paper, an innovative steel bracing system, known as the seismic response of elliptic braced moment resisting frame (ELBRF), is evaluated. ELBRF has a better structural behavior comparing to the other bracing systems and it has an architectural advantage allowing to place openings in walls with less interference. The demand for seismic performance of ELBRF is estimated through different loading patterns by adopting the conventional pushover methods. The pushover results are verified through nonlinear time history analysis (NTHAs) of 3, 5, 7, and 10-story ELBRF frames, which are on type II soil and are affected by 10 scaled earthquake records. These results are also with special moment resisting frames (SMRF) and X-Braced CBF and Inverted V-Braced CBF concentrically braced frames. Story drifts, displacements, and story shears are evaluated. A proportionally accurate estimation is observed through the pushover methods in comparison with NTHAs. Modal Pushover Analysis (MPA) can estimate the seismic demands by overcoming the shortcomings of FEMA load distributions when the higher mode effects are of concern. The seismic performance of the ELBRF system against earthquakes has improved, failure is transmitted to the upper stories, and the response modification factor is increased in ELBRF.