Reliability assessment of structures subjected to fatigue failure

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Reliability assessment of structures subjected to fatigue failure

Gayton, N. / Lemaire, M.

Structural calculation, and more especially design, is widely based on mechanical computations from characteristic values of design variables and from the so-called partial (safety) factors listed in the design rules. These design rules are the results of both designer know-how and epistemic knowledge. Their deterministic use hides the existence of the structural probability of failure due to several structural imperfections and uncertainties. Lots of structural failures are due to fatigue problems. This work aims at describing a probabilistic methodology for the calibration of partial factors for the design of structures subjected to potential fatigue failure. The general calibration procedure is based on the resolution of an optimisation problem. This solution can easily be found using optimisation algorithms when the mechanical model is explicit but it is very computer time expensive when the mechanical model is based on finite elements. This paper presents an original economical method to solve this optimisation problem. The application to fatigue problems needs the essential computation of an equivalent load factor (Thomas JJ. 2002. Fatigue modeling for automotive applications. SAE paper 2002-01-065.) briefly covered in this paper.