Structural Reliability Analysis for the Assessment of Ultimate Limit State of Ship's Hull

概要

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The aim of this paper is to establish a procedure of Structural Reliability Analysis (SRA) for the assessment of the Ultimate Limit State (ULS) of a ship's hull. Refined probabilistic models of both load (Wave-induced bending moment) and capacity (hull girder ultimate strength) have been derived using direct calculation methods based on the latest analyzing techniques. An implemental procedure of SRA for estimating the ULS of a typical merchant ship has been proposed. As application examples, a series of SRA using the First Order Reliability Method (FORM) has been performed and the annual failure probability of a tanker, bulk carrier and container carrier for the hull girder ULS has been calculated. It is found from the SRA results that the most dominant condition of large tanker is the full loading and sagging condition while the other conditions seem to he negligible. In the case of a bulk carrier, the hogging condition is also important because of the local load effect caused by sea and cargo pressures together with the sagging condition. Contrary to the previous two cases, the full loading and hogging condition is more influential in a container carrier. Based on the obtained failure probabilities of the applied ships, a reference value of the target failure probability for a ULS assessment using SRA has been mentioned.