Cost–Reliability Interaction in Life-Cycle Cost Optimization of Deteriorating Structures

Abstract

Life-cycle cost analysis of deteriorating structures has to consider not only time-varying resistance and loading affecting the reliability of these structures but also maintenance interventions applied during their lifetime. Finding the optimum maintenance scenario for a deteriorating structure is a complex process involving the selection of maintenance interventions and their application times associated with minimum life-cycle cost. There is a close relationship between maintenance intervention cost and the effect of the intervention on system reliability. However, this relationship is not included in modern structural management systems since costs of interventions are prescribed as fixed values independent on their effects on system reliability. Neglecting the interactions among maintenance interventions, their effects on structural performance, and corresponding costs leads to significant limitations of modern management systems for civil infrastructures. In this paper, maintenance intervention cost is not considered to be fixed but evaluated dynamically by using cost functions according to time-dependent variables related to the quality of intervention. The main advantages of using cost functions are the flexibility and expandability required for general purpose reliability-based structure management systems. In fact, cost functions can be used in any structure management system based on life-cycle cost. A practical example is provided to show how to establish cost functions of maintenance interventions and how these functions can be used to obtain the optimal life-cycle maintenance scenario.