Primary and deformation-induced high and low cycle fatigue reliability of infrastructure with updating through non-destructive inspection.

An efficient and economical method is proposed to mitigate fatigue and fracture damage of steel infrastructure using information from nondestructive inspections and maintenance. In spite of improvements in the design of fatigue-sensitive structures, periodic nondestructive inspections are still required by the profession to ensure an acceptable level of structural integrity. 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 nondestructive inspections. The model updating technique has been used in this study to obtain the updated information about random variables and underlying reliability index. Furthermore, the updated information on the target reliability has been 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. Also, a strategy is proposed for estimating the optimal time interval to the next inspection. Since more than one fatigue sensitive structural detail is expected to be present in a real structure, the method has been extended to consider system reliability problems. The use of system reliability to mitigate fatigue risk management is also explored. The entire procedure has been extended to consider the reliability and maintainability due to the deformation-induced fatigue as well as low cycle fatigue. The potential application of the method is demonstrated with the help of examples of steel highway bridges. 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