Sensitivity analysis of hull girder reliability in intact condition based on different load combination methods

Abstract

The paper focuses on hull girder reliability and sensitivity analysis of an oil tanker and a bulk carrier in intact condition. After a brief review of the theoretical background concerning the reliability analysis, Turkstra rule, Ferry-Borges and Castanheta, Moan and Jiao load models are applied and compared to investigate the incidence on hull girder reliability of different load combination methods for ships in full load (sagging) and ballast load (hogging) conditions. Subsequently, sensitivity analysis is carried out to investigate the incidence on the hull girder failure probability of the main parameters affecting the still-water and vertical wave bending moment stochastic processes, namely the maximum still-water bending moment reported in the loading manual, the ship voyage duration, the shape parameter of the long-term Weibull distribution of vertical wave bending moment and the mean wave period. Two reference ships, namely the ISSC oil tanker and bulk carrier, are assumed as test case for reliability and sensitivity analysis, that are performed by Monte Carlo simulation based on a dedicated programme developed in Matlab MathWorks. Obtained results are discussed and some suggestions are provided to improve the effectiveness of reliability analysis.