A structural demand model for seismic fragility analysis based on three-parameter lognormal distribution

Abstract

Seismic fragility analysis, which quantitatively describes the dynamic relationship between earthquake intensity and structural failure probability, plays an important role in the overall seismic risk assessment. An appropriate structural demand model can significantly improve the efficiency of seismic fragility analysis, and currently the most commonly used model is the lognormal model. However, recent studies have shown that this model's rationality is still in doubt. In this study, a novel structural demand model for generating analytical fragility curves in the form of a three-parameter lognormal distribution is proposed and investigated based on a large amount of nonlinear dynamic analytical data using observed Japanese ground motions with a wide range of magnitudes and epicenter distances. It shows a better fitting effect than the existing lognormal model on structural demand distribution and is expected to be more applicable to seismic fragility analysis. Through numerical fragility analysis examples on two common structural types, i.e., a steel frame structure and a reinforced concrete frame structure, the accuracy and feasibility of the proposed model are proven.