Reliability of Service‐Proven Structures

The successful past performance of an existing structure is evidence of its reliability and safety. A proof load test, for example, provides direct information on strength: the resistance of a surviving structure is shown by the test to be greater than the proof load. Accordingly, the estimate of eliability increases after a successful test. Other kinds of information can be shown to have an effect on reliability similar to proof load testing, including correlation of test and design failure modes, successful resistance to past service loading, and survival age of a structure. In the analyses, statistical techniques are used to combine a first estimate of strength with new information on the past performance of the structure, thereby obtaining an improved estimate of structural resistance. The new estimate of strength is then used in the subsequent evaluation of the structure. Increasing reliability estimates and decreasing failure rates are observed for older structures, and the likelihood of gross errors in strength is found to reduce with survival age.