Service life prediction of structural systems using lifetime functions with emphasis on bridges

In order to adequately handle the huge increase in traffic over the past three decades, most North American and European countries invested enormous funds in building highway networks. Nowadays, most of these networks are complete or close to completion. The biggest challenge highway agencies and departments of transportation face is the maintenance of these networks, keeping them safe and serviceable, with limited funds. The use of consistent measures of safety is fundamental for the development of optimum strategies for bridge maintenance. The analysis of safety on a component basis is a gross approximation of the real system performance of a bridge. In this paper, a model using lifetime functions to evaluate the overall system probability of survival of existing bridges, under maintenance or no maintenance, is proposed. In this model, bridges are modeled as systems of independent and/or correlated components. The proposed model is applied to an existing bridge located in Denver, Colorado, and the optimal maintenance strategy of this bridge is obtained in terms of service life extension and cumulative maintenance cost.