Reliability estimation with time-variant loads and resistances

This paper presents an efficient simulation-based technique to estimate the system reliability of structures that experience variation in loads and re sistance over time. To arrive at a realistic reliability estimate of such s tructures, random process description of load variation and consideration o f resistance degradation and periodic repair must be included. An adaptive importance sampling methodology for estimating the time-dependent system re liability of brittle structures is presented in this paper. In the proposed method, a simple enumeration scheme is used to identify one complete failu re sequence of the structural system. This defines the initial failure doma in to start the simulation. As the simulation progresses, the initial failu re domain is refined adaptively to include other significant failure sequen ces and to accurately estimate the failure probability of the system. The p roposed method removes the idealized simplifying assumptions of earlier ana lytical methods, facilitates easy addition of the reliability analysis modu le to structural analysis, and provides a fast and accurate estimate of thr failure probability. Numerical examples presented to illustrate the applic ation of the proposed method demonstrate its efficiency and promise.