Bridge fatigue damage evaluation and updating using non-destructive inspections

A method is proposed to mitigate fatigue damage using information from non-destructive inspections. In spite of improvements in the design of fatigue-sensitive structures, periodic non-destructive inspections are still required by the profession. A linear elastic fracture mechanics-based reliability model is proposed which incorporates uncertainties from many different sources, including uncertainty in the results obtained from the non-destructive inspections. Regardless of whether or not it detects any cracks, each inspection provides additional information and the underlying fatigue reliability needs to be updated after each inspection. The updated information on the reliability can be used as a decision making tool as what to do next, in terms of whether to do nothing, reschedule the next inspection at an earlier date, or repair or replace the structure immediately. The application potential of the method is demonstrated with the help of examples. It is shown that the proposed method is much superior to the current S-N curve-based AASHTO method and can be used as an alternative to it.