The economics of maintenance repair and strengthening of arch bridges

Most of the masonry arch bridges in the UK were built before 1922, and the weight and volume of traffic using them has greatly increased since then, and caused concern. There has recently been renewed interest in them, because the lack of methodology to assess and value them have been major issues. This paper presents some principles of quantification involved in evaluating them. The stock of road bridges should be managed with the following objectives. There should be minimal disruption to transport, acceptable standards of structural safety should be maintained, and national assets and resources should be used wisely. Thus structures should have long-life materials and components, requiring minimal attention. The main considerations in formulating a rational policy for evaluating bridges are how to: use insurance to aid decisions, assess risk, and calculate economic consequences. Cost-benefit analysis and statistical decision theory need to be applied. The economic consequence of failure of bridges are derived from: (1) loss of life from failure; (2) loss of utility while repairs proceed; (3) cost of replacing or repairing a bridge; and (4) cost of public and political over-reaction, ie the cost of the uneconomic over-provision of repair and strengthening following spectacular failures.