Evaluating the impact of intensity measure selection on conditional seismic risk

Rudman, A. and Douglas, J. and Tubaldi, E. and Scozzese, F. and Turchetti, F. (2023) Evaluating the impact of intensity measure selection on conditional seismic risk. In: 18th World Conference on Earthquake Engineering, 2024-06-30 - 2024-07-05. (In Press)

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Abstract

Conditional methods for seismic risk assessment, such as those at the basis of FEMA P-58, are reliant on the selection of an intensity measure (IM). The importance of selecting the right IM (e.g., sufficiency and efficiency) to accurately assess structural performance is well known. A wide range of IMs exist in the literature, with different IMs considered suitable for investigating damage to different structural types or components. Nevertheless, there has been little study on the impact that IM selection has on risk and damage assessments. Therefore, this study aims at evaluating the impact that IM selection has on damage estimates using FEMA P-58 component-level procedures. We first establish a hypothetical scenario that consists of a site located at the centre of a circular seismic source zone and two line sources, where earthquakes follow a Gutenberg-Richter relationship between magnitude 5 and 7.5. Ground motions at the investigated site are simulated through the application of a non-stationary stochastic ground motion model. This allows the rapid creation of many realistic ground motion records, helping to fully capture the uncertainty in risk estimates using different IMs. A variety of IMs are calculated from each simulated ground motion, with hazard estimated from these. Structural analyses are then performed on a mid-rise steel moment-resisting frame, using the same set of ground motions, to estimate fragility for a range of component-level engineering demand parameters (EDPs). Conditional risk estimates are produced through convolution of the hazard and fragility from IM-EDP combinations, with damage predicted from these. Damage estimates are compared against each other and against a benchmark solution obtained via the unconditional approach (directly estimating damage state exceedance frequencies from data), allowing the suitability of each IM to predict damage to be judged.

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