PRACTICAL RELIABILITY ANALYSIS OF LINEAR LIFELINES UNDER NATURAL HAZARDS

A study to develop a methodology for a practical reliability assessment of linear lifelines under natural hazards such as earthquakes is reported. The assessment consisted of estimating probabilities of attaining various levels of functional goals for the lifeline and evaluating a damage probability matrix. A salient feature of the investigation was the consideration of dependency between adjacent sections or spans of a lifeline. Two types of probabilistic models were used--binomial and bivariate normal. In both cases a pairwise dependence was assumed. The methodology was applied to two sample problems: a three-span concrete bridge whose geometry and problems were based on an existing ten-span bridge in Oakland, California, and an underground pipeline based on the Trans-Alaska pipeline located in a seismically active area. For the bridge example, lifeline failure was assumed to occur when a complete failure mechanism developed; pipeline failure was assumed to occur when applied axial strains exceeded yield strains. Results demonstrated that this methodology can be applied successfully to a variety of lifelines, can predict and analyze damage, and can aid decisionmaking with respect to replacing a damaged lifeline or making major repairs.