Maintenance planning for deteriorating concrete bridges

In an effort to prioritize the repair, rehabilitation, and replacement of e xisting bridges, bridge management programs have been developed. In recent years, reliability-based optimum-maintenance planning strategies applicable to bridges have been proposed. Optimum inspection and repair times can be identified using these strategies. In this study, the effect of repair on t ime-variant failure probability is illustrated for several repair/replaceme nt strategies. Time-variant reliability computations are performed using a combined technique of adaptive importance sampling and numerical integratio n. Several repair strategies are investigated for a typical bridge in Color ado. For this bridge, it is shown that for a single repair performed about halfway through the design life, the postrepair strength must be at least 8 0% of the original strength for the repair to have a significant influence on the system failure proability of the bridge during its remaining service life. Also, for maintenance using shotcrete, multiple repairs appear to ha ve little influence on the lifetime system failure probability. Also presen ted are optimal maintenance strategies in which optimal inspection/repair t imes are identified based on minimum expected cost within prescribed reliab ility constraints. It is shown that the optimum repair time is dependent on the failure cost of the bridge and that the discount rate influences the o ptimum repair time and life-cycle cost. As the discount rate increases, the optimum repair time increases until it reaches an upper bound that is depe ndent on the system failure probability constraint. The results can be appl ied to the prediction of optimal lifetime maintenance planning Strategies f or concrete bridges under corrosion.