document: In this work, a numerical strategy for designing an optimal maintenance scheduling for a structure, accounting explicitly for the effects of uncertainty is suggested. This contribution, which can be regarded as an extension of the methods developed in [23], presents several novel aspects over similar approaches proposed in the literature. Firstly, the initiation and propagation of fatigue crack is modeled efficiently by means of cohesive zone elements [24–26]. The application of this class of elements allows modeling the crack initiation and propagation within a unified framework. It should be noted that cohesive zone elements have already been used for uncertainty quantification of the crack propagation phenomenon [27,28]. However its application within the context of maintenance scheduling constitutes a novelty. The second innovative aspect of this contribution refers to the assessment of the reliability sensitivity with respect to the variables that define the maintenance scheduling. The estimation of this sensitivity, which is required in order to determine the optimal maintenance schedule within the proposed framework, can be quite demanding as the model characterizing repair of a cracked structure leads to a discontinuous performance function associated with the failure probability. A new approach for modeling this function is proposed herein. The continuous and discontinuous parts respectively of the function are considered separately to estimate accurately the gradients of the failure events.
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