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.

提出了一种预测地震作用下钢筋混凝土抗弯框架非弹性位移的新方法。该方法对前几个重要模式使用模态行为（或强度降低）因子，这些因子是周期，层间漂移比，塑性旋转，性能水平和土壤类型的函数。出于设计目的，第一作者过去已经得出了这些因素的明确经验表达式。这些因素在这里用于非弹性位移预测。因此，这些因素乘以相应的弹性模态位移以产生非弹性模态位移，这可以通过像SRSS规则这样的组合规则提供非弹性模态位移。