Maintenance strategy for bridges using reliability concept and analytical hierarchy process

Abstract

Civil infrastructure in most of countries is getting old and therefore, there is a tremendous need to assess their safety levels. Among civil infrastructure, bridges are one of the main components and there is a need to study more on their safety and durability to minimize the maintenance cost and to avoid sudden failures. This paper presents bridge maintenance strategy which consists of two parts: (1) reliability based condition assessment procedure and; (2) analytical hierarchy process (AHP) based resources prioritization. In reliability based assessment, safety margins are initially proposed depending on the types of bridges. It is assumed that load and strength are random variables. Elementary reliability indices and thereby elementary failure probabilities are estimated for each safety margins. Then, system failure probability of the bridge is calculated for the time of consideration. Finally, this system failure probability is used to get system reliability index of the bridge and it is used as an index to express the condition of the bridge for the considered time. Secondly, AHP is implemented to identify the order of resources prioritization among set of bridges. The selected criteria are safety, cost of maintenance actions and relative importance of the bridge. Relative importance varies depending on historical importance, age and route of bridge location. The proposed methodology is applied to a collection of five bridges in Sri Lanka to estimate their safety levels and resources prioritization in bridge maintenance.