A Study on the Effect of Aleatory and Epistemic Uncertainties on Fragility Curves of Steel Moment Frames

The aim of this study is to investigate the effect of aleatory and epistemic uncertainties on seismic performance of an intermediate steel moment frame. For this reason, generalized incremental dynamic analysis is employed. To model record-to-record aleatory uncertainties, 40 far-field ground motion records are utilized. Also, to model important epistemic uncertainties, 5 parameters of plastic hinge behavior are uncertainly modeled and statistical parameters are considered for these models. Then, by using effective simplified models of random variable production, 50 combination of these 5 parameters are produced and for each one of these models a bin of IDA curves are extracted. Results show that parameters with epistemic uncertainty affect fragilities of IO limit state more than other limit states. In other words, for CP and GI limit states fragilities of mean of models yield acceptable results even when incremental dynamic analysis cannot be conducted for all the 50 models. However, For IO level, the effect of epistemic uncertainties cannot be neglected.