Cloud-IDA-MSA Conversion of Fragility Curves for Efficient and High-Fidelity Resilience Assessment

In performance-based earthquake engineering framework, seismic fragility functions play a fundamental role for quantifying the seismic resilience. There are three main approaches for performing the seismic fragility analysis: cloud analysis, incremental dynamic analysis (IDA), and multiple strip analysis (MSA). These approaches require different levels of computational efforts and yield different levels of accuracy on fragility curve estimates, leading to different predictions of seismic resilience. This paper presents an efficient method for converting fragility curves from the cloud to IDA and MSA and from IDA to MSA toward an efficient and high-fidelity resilience assessment. The proposed method requires two fragility points to obtain the fragility median and dispersion parameters that yield converted fragility curves agreeing with the target fragility curves. This method and associated resilience assessment are demonstrated through two case studies, one a typical two-span highway bridge in firm ground under longitudinal seismic excitations and the other an extended pile-shaft-supported bridge in liquefaction-induced laterally spreading ground under transverse seismic excitations. The results show that the converted fragility curves coincide very well with the target fragility curves. An efficient and high-fidelity resilience assessment can be achieved leveraging the proposed method. For easy implementation, codes of the proposed method are available online. (C) 2021 American Society of Civil Engineers.