Reliability Analysis of Elasto-Plastic Structures under Variable Loads

Structural reliability analysis is based on the concept of a limit state function separating failure from safe states of a structure. The paper discusses some difficulties of different reliability methods for FEM-discretized nonlinear structures. It is proposed that theorems of limit and shakedown analysis are used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. Shakedown describes an asymptotic and therefore time invariant structural behaviour under time variant loading. The limit state function and its gradient is obtained from a mathematical optimization problem. For application to large FEM models a basis reduction method is used. The method is implemented into a general purpose FEM code. Combined with FORM highly effective, robust and precise analyses could be performed for high-reliabilty problems.