Abstract

RUIZ-GOMEZ, Sonia E.; TOLENTINO-LOPEZ, Dante  and  TORRES PEREZ-NEGRON, Marco A.. Time-Dependent Confidence Factor for Structures With Degradation Caused by Fatigue. Ing. invest. y tecnol. [online]. 2014, vol.15, n.3, pp.377-390. ISSN 2594-0732.

An approach to evaluate the confidence factor for structures at the end of an interval of time is proposed. The confidence factor indicates the adequacy of the performance level of a structure subjected to external loads. The factor considers the uncertainties implicit in the structural capacity and in the structural demand. The formulation is made in accordance with the Demand and Capacity Factor Design Format. Four scenarios are compared: a) structural capacity deteriorates over a time interval, while structural demand remains constant, b) only structural demand (for a given intensity) varies in time, c) both structural capacity and structural demand vary simultaneously in time, and d) the effect of structural deterioration is neglected. The approach is applied to an offshore jacket platform. Deterioration is taken into account by analyzing the growth of fatigue cracks in both ends of several critical structural elements. It is concluded that for the evaluation of the confidence factor over an interval of interest, for the case analyzed, it is more significant to consider the variation in time of the structural capacity rather than that of the structural demand; however, it is recommended to consider both (structural capacity and structural demand) in the analysis.

Keywords : confidence factor; structural deterioration; fatigue; reliability; jacket offshore platform.