Optimum Target Reliability Determination for Efficient Service Life Management of Bridge Networks

Abstract

In order to ensure structural safety, deteriorating bridges should be maintained above their target reliability level. This level affects the optimum maintenance interventions during the service life of a bridge. Therefore, it is necessary to determine the target reliability level of an individual bridge in a rational way. This paper introduces a novel probabilistic approach for determining the target reliability of an individual bridge for service life management at the bridge network level. The target reliability index of a bridge can be determined using a structural importance indicator and can be computed through an optimization process. In the structural importance indicator method, the target reliability index of a bridge is assigned according to the structural importance indicator of the bridge in a network. Multiobjective optimization is formulated based on four objectives: maximizing the reliability, minimizing the expected maintenance cost, minimizing the expected user costs, and maximizing the redundancy of the bridge network. The design variables of this optimization problem are the target reliability indices of the individual bridges in the network. The reliability, expected maintenance cost, expected user cost, and redundancy of the bridge network are compared considering single and multiple target reliability indices applied for the individual bridges. An existing bridge network is used to illustrate the application of the proposed approach.