Global seismic fragility analysis of structures based on reliability and performance

Seismic risk analysis includes three aspects,i.e.,seismic hazard analysis,seismic fragility analysis and seismic loss assessment. Among the three contents,the seismic fragility analysis is very important to seismic design,retrofit and upgrading decision-making of engineering structures in that it can predict the probability of unfulfilling the prescribed levels of performance requirements under all levels of seismic actions.Traditionally,the seismic fragility curves are depicted by using empirical methods or Monte Carlo simulation methods.In this paper,the basic principles of seismic risk analysis are firstly introduced,and then,the concept of global seismic fragility of structures is put forward.To overcome the problems in the traditional methods,a new method for global seismic fragility analysis of structures is proposed by combing the methodologies of structural reliability with the theory of performance-based seismic design,the seismic fragility of structures is computed by way of the finite element reliability methods.Taking the maximum storey-level relative deformation of structures as a global seismic performance index,the seismic fragility is analyzed for a five-storey,two-bay steel frame structure,and the seismic fragility curves corresponding to different performance levels under three levels of seismic actions are depicted by using the proposed method.