Reliability assessment of pile-supported structural systems

A performance-mode (PM)-based evaluation procedure is proposed to determine the probability of unsatisfactory performance (UP) for two-dimensional (2-D) and three-dimensional (3-D) systems involving pile-supported dams. This methodology includes ductile behavior of individual piles for the strength mode. It also examines the 3-D effects on the bounds for the series-parallel system. The procedure is an extension of the reliability method presented to compute the system probability of UP of pile-supported structures using brittle-element behavior. Lateral and vertical deflections are the limit states of the pile cap that provide the system-level probability of UP for the serviceability limit state. The element-level probability of UP for strength and system-level probability of UP serviceability are combined to evaluate the bounds for the load-case specific system probability of UP. Finally, the overall system probability of UP is evaluated considering the contributions of all load cases combined. The procedure is illustrated wilh examples, and the bounds for the system probability of UP are evaluated. The results indicate that the bounds of probability of UP for the example are narrower for ductile behavior than for brittle behavior. A 3-D problem correctly recognizes a number of significant PM that are absent in the 2-D approximation.