Comparison of two reliability assessment methods for the seismic performance of timber-steel hybrid structures Lam, Frank; Li, Zheng; He, Minjuan; Li, Minghao
The seismic performance of a multistory timber-steel hybrid building system with steel moment resisting frame, timber-steel hybrid diaphragms, and in-fill light frame wood shear walls has been studied. This paper focuses on the seismic reliability of the lateral load resisting system in such hybrid structures. The seismic performance of such hybrid systems has been evaluated using two reliability assessment methods with the consideration of the uncertainties from ground motion, intensity measure and structural resistance. One method was the fragility analysis which calculates the exceeding probability of drift demand from conditional distributions under given seismic intensity levels. Combined with a seismic hazard analysis, the failure probabilities for the timber-steel hybrid systems were obtained. The other method was response surface method (RSM), and polynomial functions were used to represent the seismic response surfaces. Non-performance probabilities were then evaluated by FORM with respect to different performance targets. Results from the two methods were compared showing similar results. However, the reliability indices obtained from RSM were lower than those obtained from fragility analysis. This was mainly due to the additional uncertainties considered in RSM. The associated reliability indices and failure probabilities for the timber-steel hybrid structures were also presented. Both methods may serve as tools for the reliability assessment of timer-steel hybrid structural systems, which supports more of its practical applications.
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