System reliability evaluation considering strength and serviceability requirements

A robust system reliability evaluation method is proposed for aging redundant structures. Pile-supported structures commonly used for darns are specifically addressed. The individual pile behavior is considered to be brittle-type and the group behavior is considered to be parallel-type. Both strength and serviceability performance modes are considered. Using the advanced first-order second-moment reliability method, the element-level reliability indices are calculated for individual piles for several strength limit states. The system-level reliability indices of the pile group are calculated considering the lateral and vertical deflection limit states. Using the performance mode approach, which is referred to as the failure mode approach in the literature, a procedure is proposed to identify significant performance modes of the system by combining the element-level and system-level reliabilities. The bounds of the system reliability are then estimated. The procedure is first verified using information from load tests. The method is then applied to estimate the bounds of system reliability for a pile-supported dam. Identification of the significant performance modes becomes easier using the proposed method. It is observed that the values used for the allowable lateral and vertical deflections are critical in the overall system reliability evaluation. The lower and upper bounds of the system reliability are observed to be narrow for the examples considered in the study. The proposed procedure significantly improves the state of the art in the evaluation of system reliability of pile-supported structures. Copyright (C) 1996 Elsevier Science Ltd.