Reliability Calibration of Fatigue Evaluation and Design Procedures

Abstract

Fatigue evaluation and design methods were developed in a recent project for steel highway bridges. The evaluation method enables an engineer to estimate the safe remaining life of an existing bridge. The estimate of safe remaining life is needed to make cost‐effective decisions regarding inspection, repair, rehabilitation, and replacement. The design method is consistent with the evaluation method. The reliability‐based concepts and data base behind the development of these methods are discussed and illustrated through some examples. The evaluation and design methods were calibrated for both redundant and single‐load‐path bridge components using safety (reliability) indices computed with existing fatigue specifications. The proposed procedures lead, however, to more uniform and consistent safety indices. The evaluation and design methods also follow to a large degree present procedures familiar to highway agencies. These methods, however, contain options to use site‐specific traffic and inspection data and improved structural analysis. Both the evaluation and fatigue design methods have been incorporated in two recent guide specifications published by AASHTO.