Life-cycle cost-benefit (LCCB) analysis of bridges from a user and social point of view

During the last two decades, important progress has been made in the life-cycle cost-benefit (LCCB) analysis of structures, especially offshore platforms, bridges and nuclear installations. Due to the large uncertainties related to the deterioration, maintenance, and benefits of such structures, analysis based on stochastic modelling of all significant parameters seems to be the only relevant analysis. However, a great number of difficulties are involved, not only in the modelling, but also in the practical implementation of the models developed at present. The main purpose of this paper is to present and discuss some of these problems from a user and social point of view. A brief presentation of a preliminary study of the importance of including benefits in life-cycle cost-benefit analysis in management systems for bridges is shown. Benefits may be positive as well as negative from the user point of view. In the paper, negative benefits (user costs) are discussed in relation to the maintenance of concrete bridges. A limited number of excerpts from published reports that are related to the importance of estimating user costs when repairs of bridges are planned, and when optimized strategies are formulated, are shown. These excerpts clearly show that user costs in several cases completely dominate the total costs. In some cases, the user costs are more than ten times higher than the repair costs. A simple example of how to relate and estimate user costs to the repair of a single bridge is shown. Finally, how the total maintenance costs (including user costs) may be estimated for a large bridge stock is discussed. This paper is based primarily on two previous International Association for Bridge Maintenance and Safety (IABMAS) conference papers by Thoft-Christensen (2004b, 2006).