Determining seismic fragility of structures and components in nuclear power plants using multiple ground motion parameters - Part I: Methodology

This study proposes an innovative fragility method that overcomes the problems in the existing method by using multiple ground motion parameters, providing more realistic seismic capacity and fragility estimates of structures and components. By incorporating the correlations among spectral accelerations at structural dominant modes and the commonly used ground motion parameter such as peak ground acceleration, the conservatism in seismic responses is effectively reduced, in turn resulting in higher seismic capacity estimates of structures and components. Given the advantages of the proposed method, the computational cost is deemed acceptable for applications. The proposed fragility method should be implemented in Seismic Margin Assessment and Seismic Probabilistic Risk Assessment, improving the seismic capacity estimates of the critical structures and components that limit the overall plant seismic capacity. The companion paper (Part II) presents an application of the proposed method to a horizontal heat exchanger in Darlington nuclear generating station in Ontario, Canada to illustrate its procedure and to demonstrate its benefits.