Evaluation of RSA based formula for critical responses and incidence angles of a concrete MRF subjected to ground motions scaled to different hazard levels

Seismic analysis of structures often requires applying a pair of ground motions simultaneously in the directions of the structures since an earthquake can excite with any incidence angle. Critical response and incident angle analysis therefore play a significant role in seismic structural design by predicting maximum structural responses. Existing procedures are often based on response spectrum analysis methods (RSA) to obtain critical angles and responses. The main objective of this study is to compare the critical incidence angles and responses obtained with response history analysis (RHA) and RSA for a concrete moment resisting frame (MRF). Unlike previous studies, this study considers the effect of different hazard levels by using different scaling methods for a total of fourteen selected pairs of recorded ground motions. Response history analyses of a nine-story concrete MRF are conducted under different seismic hazard levels. The studies demonstrate the significance of critical angle analysis as well as some discrepancy between RHA and RSA.