ABSTRACT
The concept of system reliability will be described in this chapter. A moment-based method for assessing the system reliability of series and non-series structures is investigated, with emphasis on series systems. The reliability index is directly calculated based on the first few moments of the system performance function of a structure. It requires neither the reliability analysis of the individual failure modes nor the iterative computation of derivatives, the computation of the mutual correlations among the failure modes, and any design points. As a practical topic, the evaluation of system reliability for ductile frame structures using methods of moment is introduced in the final part of this chapter. The difficulty in both failure mode identification and failure probability computation is still hard to overcome when using the traditional method for the system reliability assessment of ductile frame structures. To avoid the difficulties, a failure mode independent performance function with weak non-normality is introduced. The method of moments is then utilized to estimate the failure probability of ductile frame structures corresponding to the general performance function. From the numerical examples, it can be concluded that the introduced methodology successfully overcomes the two difficulties including the identification of significant failure modes and the computation of overall failure probabilities contributed from these significant modes in system reliability evaluation of ductile frame structures.
