Determining the optimal structural target reliability of a structure with a minimal life-cycle cost perspective

This study presents a methodology for determining the optimal target reliability of a civil structure using the life-cycle cost (LCC) concept. The relationship between the reliability index and the estimated LCC is analyzed in order to find optimal target reliability. As a simple explanation of the method, the study uses steel bridges as an example. The analysis reveals that the LCC of steel bridges has great influence on target reliability, especially when the bridges have many lanes and long spans. It is also ascertained that higher target reliability is required to minimize the LCC when the number of lanes or average daily traffic (ADT) increases. Reliability analyses considering various traffic conditions were also conducted to observe changes in structural reliability with regard to such conditions. After the optimal target reliability is determined, target reliability adjustment can be performed. The analysis results show that the target reliability index can be adjusted consistently within the appropriate ranges by modifying the resistance factor in a limit state equation. In the last part of the study, an example bridge case study was performed to confirm the possibility of practical application of the presented method.