Evaluation of the MPA Procedure for Estimating Seismic Demands: RC-SMRF Buildings

Abstract

The modal pushover analysis (MPA) procedure is extended for analysis of reinforced concrete special moment resisting frame (RC-SMRF) buildings, after demonstrating that the theory, assumptions, and approximations underlying this procedure are valid for such systems. The principal extension of the procedure is in the hysteretic model for modal SDF systems, chosen as the peak-oriented model to represent the global monotonic and cyclic behavior of such buildings, characterized by deterioration of stiffness and strength under cyclic deformation. The median seismic demands for 4-, 8-, 12-, and 20-story RC-SMRF buildings—designed to comply with current codes—due to an ensemble of 78 ground motions scaled to four intensity levels were computed by MPA and nonlinear RHA, and compared. It is demonstrated that, even for the most intense ground motions that deform the buildings far into the inelastic range, the MPA procedure demonstrates an adequate degree of accuracy that should make it useful for practical application in estimating seismic demands for RC-SMRF buildings. In contrast the FEMA-356 force distributions are inadequate in estimating seismic demands for the 8-, 12-, and 20-story buildings at all excitation intensities, from the weakest that causes response essentially within the linearly elastic range, to the strongest that drives the buildings far into the inelastic range.