Effect of Uncertainties on Seismic Response of Steel Moment-Resisting Frames Affected by Sequence of Mainshock-Aftershock Earthquakes

The inherent uncertainties in the structural capacity and earthquake demand can significantly influence the performance of the structures under mainshock-aftershock sequences. In this regard, fragility models are robust tools for calculating cumulative damages considering uncertain parameters in both demand and capacity. However, some uncertain parameters need to be examined together to determine how they might affect the fragility analysis of steel frames. This study presents a robust fragility assessment method for steel moment-resting frames under key modeling uncertainties and a suite of real mainshock-aftershock sequences. The case studies are 4- and 12-story steel moment-resisting frames with different uncertain parameters. The simulation results are used to estimate the probability of exceeding different damage states. The results confirm the importance of including uncertain parameters for proper seismic assessment.