A practical method to assess time-dependent structural system reliability

Abstract

Time-dependent structural system reliability problems are those in which the applied loads are modelled as stochastic processes, and the structural resistances are changing (usually deteriorating) with time and/or loading or both. Although the state-of-the-art approaches in time-dependent structural system reliability analysis are quite successful, it has been noted that the development of these approaches has not yet reached the stage that practising engineers are able to employ time-dependent reliability theory in their design work. The problem is that time-dependent reliability theories have not been simplified significantly for practical design purposes, and that the formulation of the problem is too mathematical. The aim of this paper is to introduce a practical, relatively simple method to estimate time-dependent structural system reliability for realistic engineering structures, with the reliability analysis based on the reliability of the structural components which form a collapse mechanism. The proposed method is practical and simple since it avoids the necessity of using limit state functions for the structure as a whole, as is required in other approaches. In addition, the mathematical concepts and the formulation have been simplified by using only second moment representation for both time-invariant and time-variant parts. An example is given to illustrate the method.