Life-time reliability based optimization of bridge maintenance strategy considering LCA and LCC

Abstract

Maintenances are necessary to ensure the safety and serviceability of existing bridges. With the increasing number of existing bridges, maintenances cost a large proportion of financial fund and have significant impact on environment. Implementation of preventive maintenance (PM) could reduce the frequency of essential maintenance (EM) and corresponding cost, leading to considerably lower environmental impact of maintenances. Different from planning of EM, which depends on the structural condition of an existing bridge, PM is periodical. Selection of initial time and time interval of PM will influence the life cycle cost and environmental impact of existing bridges. In this study, a framework for the maintenance scheme optimization of existing bridges based on the genetic algorithm was proposed. Maximum safety, minimum life cycle cost and life cycle environmental impact were taken as optimization objects to find a more rational initial time and time interval of PM of the bridges. To verify the effectiveness of the proposed optimization procedure, a case bridge was selected and the cumulative failure probability, life cycle cost, and life cycle environmental impact of the case bridge with different maintenance schemes were calculated. An optimal maintenance schemes set of the case bridge was obtained. Comparison among the optimal schemes and the scheme without PM was conducted. It can be concluded that PM is of great importance on bridge management. Selection of the initial time and time interval of PM rationally would decrease the bridge's life cycle environmental impact effectively. The reduction of the life cycle cost of the bridge caused by maintenance scheme optimization is not significant. This is because that time value of cost was considered by introducing discount rate into the framework.