This paper presents a formulation for developing seismic demand models and estimating fragilities for reinforced concrete (RC) structures under mainshocks (MSs) only and mainshock-aftershock (MS-AS) sequences. The demand model for the MS only is a function of the MS intensity, while the model for the MS-AS sequence is a function of two variables, one describing the MS and one describing the AS. A Bayesian method is used to calibrate the demand models. The demand models are then used to estimate the fragility of RC structures. Predictive fragility curves are developed to include the uncertainties in the model parameters estimated by Bayesian approach, and confidence bounds of the fragility curves are developed to separate the effects of the uncertainty in the model parameters from the other sources of uncertainties. The proposed formulation is illustrated using a typical five-story RC frame building. The results show that the fragility curves for MS only tend to significantly underestimate the fragility curves for MS-AS sequences. Also, the uncertainty in the fragilities for the MS-AS sequence is, as expected, larger than that considering only the MS.

本文提出了开发地震需求模型和估计钢筋混凝土 (RC) 结构在仅主震 (MS) 和主震-余震 (MS-AS) 序列下的脆性的公式。仅MS 的需求模型是MS 强度的函数，而MS-AS 序列的模型是两个变量的函数，一个描述MS，一个描述AS。贝叶斯方法用于校准需求模型。然后使用需求模型来估计钢筋混凝土结构的脆弱性。开发预测脆弱性曲线以包括通过贝叶斯方法估计的模型参数中的不确定性，并且开发脆弱性曲线的置信界限以将模型参数中的不确定性的影响与其他不确定性来源分开。使用典型的五层钢筋混凝土框架建筑说明了所提出的公式。结果表明，MS 的脆性曲线只会显着低估 MS-AS 序列的脆性曲线。此外，正如预期的那样，MS-AS 序列的脆弱性的不确定性大于仅考虑 MS 的不确定性。