Comparison of methods for computing the probability of failure in time-variant reliability using the outcrossing approach

Time-variant reliability aims at assessing the probability of failure of a structure over a given lifetime. The classical approach uses the outcrossing theory and analytical results (asymptotic integration) to solve the problem. Specific tools have to be used to implement the method. In this paper, a new approach called PHI2 method is presented as a way to address the issue by using classical time-invariant reliability tools, such as the FORM method. Both approaches are compared in simple cases where closed-form solutions to the reliability problem exist. The comparison shows that PHI2 provides almost exact results in all cases under consideration. Finally a more realistic problem is solved, namely that of the failure of a bending beam submitted to both corrosion and random loading.