Estimating the Timing of Rehabilitation and Replacement of Bridge Elements

The core component of infrastructure management systems is life-cycle costing, typically used to justify the appropriate actions to the infrastructure at the best times during service life. This paper presents the results of a study on the timing of such actions, with emphasis on state-maintained highway bridges in Florida. Using historical cost data of maintenance, repair, rehabilitation, and replacement of bridge elements, the authors present and discuss basic statistical summaries of the age of bridges when the actions were applied. From the concept of age replacement models, an estimate was computed for the optimal ages at which to rehabilitate or replace some bridge elements. Weibull-type distributions were obtained as the best-fitting probability distributions of the time until a failure. “Failure time” is a term borrowed from operations research, where it implies the end of service life of items or systems, but here it means when it is necessary to repair or replace a bridge element. Optimization was then performed according to reliability models developed to minimize the average long-run costs per year on rehabilitation and replacement of the bridge elements. Advantages and limitations of the results are discussed. The proposed methodology has good potential to help the bridge manager estimate service life of bridge elements, with a consideration of the repair policy. Limitations to the direct implementation of the methodology exist, but some improvement can be achieved with future research.