Applicability of Nonlinear Static Procedures to RC Moment-Resisting Frames

The applicability of nonlinear static procedures for estimating seismic demands in a variety of building types was evaluated within the recently concluded ATC-76-6 project. Results are reported herein for several pushover methods applied to three RC moment frame buildings, relative to baseline data provided by nonlinear response history analysis. Response quantities include peak interstory drifts, floor accelerations, story shears, and floor overturning moments. The single-mode pushover methods that were evaluated include the N2 and ASCE 41 coefficient methods. Multi-modal pushover methods include the modal pushover with elastic higher modes, and the consecutive modal pushover. Target displacements were estimated using typical R-C1-T relationships. Results indicate that the good performance of the single-mode methods for low-rise buildings rapidly deteriorates as the number of stories increases. Multi-mode techniques generally can extend the range of applicability of static pushover methods, but at the cost of significant additional computation and with uncertainty about the reliability of the results.