STRUCTURAL SYSTEM RELIABILITY BY THE METHOD OF STABLE CONFIGURATION

A physically meaningful approach for the reliability analysis of structural systems having elasto-plastic and elastic-brittle components is presented. Practical approximations and simplifications to the theoretical stable configuration approach (SCA) are derived from the cut-set formulation based primarily on the dominant physical configurations of a given structure.; The first step in implementing the proposed method involves the component performance functions of the initial configuration and those of the dominant configurations (corresponding to one failed component). The geometric average of the second-order bounds for the probability of the union of failure events is used in the computation of the failure probability of each configuration. An upper bound estimate of the system failure probability is then computed using an analogue of Boole's inclusion-exclusion formula. This estimate is then used as a criterion for selecting other dominant configurations (corresponding to more failed components). The final system reliability is estimated through the intersection of events corresponding to all the selected dominant configurations using the second-order upper bound for the probability of an intersection.; A number of example problems were examined and the results were used also to validate the accuracy of the proposed SCA. The method was shown to be particularly effective for the class of structural systems composed of elastic-brittle components. For ductile systems, the SCA does not have much advantage over the traditional failure mode approach (FMA).; Using the numerical examples, the concept of structural redundancy is examined. Conventionally, the degree of indeterminancy of a structure is associated with the structural redundancy. However, other factors also influence redundancy, including the material behaviour of the components, the topology of the structure and the correlation between the capacities of the components. The percentage of redundancy of a structure, defined in terms of the ratio of the probability of collapse to the probability of initial damage, is introduced as an alternative measure of structural redundancy.