An Optimized Lifetime Reliability-based Inspection Program for Deteriorating Structures

No matter how well they are designed, all civil engineering structures will deteriorate over time and a program of lifetime inspection, maintenance and repair represents a substantial portion of the total lifetime cost of most structures. An optimized inspection program is the key to making appropriate repairs at the right time to minimize cost and maintain an appropriate level of safety in a structure. When a visual inspection will not provide the necessary level of information, some other non-destructive evaluation method is often needed. This study summarizes a methodology for optimizing the timing, the frequency, and the type of inspection over the expected useful life of deteriorating structures. A decision tree analysis is used to develop an optimum lifetime inspection plan which can be updated as inspections occur and more data is available. This methodology is illustrated using a half-cell potential test on a deteriorating concrete bridge deck. The study includes the expected life of the structure, the minimum prescribed safety level of the structure, costs of inspection and specific repairs, discount rates, the capability of the test equipment to detect a flaw, and the management approach of the owner towards making repairs. The optimum strategy can be updated after each inspection to incorporate new data.