Target Reliability for Fixed Offshore Structures, Calibrating API Probability Based Fatigue Design Criteria

Abstract

One of the most important considerations when developing a design code based on reliability concept lies in the choice of target reliabilities (or allowable failure probabilities) for the structure/elements. The choice is generally made by a process of probabilistic calibration to existing design codes. There are various feasible designs which satisfy the design code ; therefore, it is expected that lifetime reliabilities corresponding to those designs will be distributed with large spread. In this study, the reliabilities corresponding to the minimum weight design within the specified constraints of the design code are interpreted as the target reliabilities, and the algorithmic procedure is proposed for the evaluation. The proposed procedure is applied to the calibration of API (American Petroleum Institute) PR2A, a design code for fixed offshore structures, whose fatigue design criteria for tubular joints were revised on basis of structural reliability analysis of level 2.