Analysis of the failure costs of a bridge

The preferable maintenance strategy for aged bridges is the one which involves the lowest possible total cost for the community, where for each bridge the total cost is expressed by the sum of the costs of the interventions plus total damages caused by exceeding the limit states multiplied by the probability of exceeding the limit states.

The most delicate and most complex part of the calculation is the determination of damages since the uncertainties involved are many and the values of these parameters may significantly impact on the results of the calculation. Each damage can be estimated as the sum of direct costs (reconstruction of the collapsed part, social consequences like injuries and fatalities, environmental effects) and indirect damages (infrastructure disruption, psychological effects).

Direct costs are quite easy to calculate, but they are also the least significant items. We could evaluate the huge amount of indirect costs using the studies available in literature and also learning from past accidents. Today we know the economic and social consequences of many historical collapses, so it is possible to find out which factors influence the results the most and to determine the real magnitude of each type of damage. In this article many indications are provided to make a reliable estimate of the failure costs for a generic bridge.