Prediction of seismic inelastic displacement profiles of R/C moment resisting frames

Abstract

A new method for predicting inelastic displacements of reinforced concrete moment resisting frames under seismic motions is presented. The method uses modal behavior (or strength reduction) factors for the first few significant modes, which are functions of period, interstorey drift ratio, plastic rotation, performance level and soil type. Explicit empirical expressions for these factors have been derived by the first author in the past for design purposes. These factors are used here for inelastic displacement prediction. Thus, these factors are multiplied by the corresponding elastic modal displacements to produce the inelastic modal displacements, which can provide the inelastic displacements via a combination rule like the SRSS rule. The proposed method is compared against the equal displacement rule and three other well-known methods on the basis of nonlinear time history analyses and its merits are demonstrated.