Ultimate limit state analysis of a double-hull tanker subjected to biaxial bending in intact and collision-damaged conditions

Abstract

This study presents a comparison between nonlinear finite element analysis (FEA) and the Smith method of Fujikubo et al. (2012). The objective was to compare the accuracy and computation effort of the two methods for a double-hull tanker under biaxial bending and various ship conditions: intact hull structure, collision-damaged hull structure, newly built condition, and ship hull aged due to corrosion. The results for the non-corroded and intact ship hull structures showed good agreement between FEA, the Smith method and IACS CSR-H for vertical bending loading conditions. For all other bending load combinations, FEA always gave lower ultimate bending moments than the Smith method. The differences between the two methods were larger for the corroded and damaged ship hull structure than for other conditions. Results from ultimate strength analyses of the collision-damaged hull structures showed that both methods captured the expected asymmetric ultimate strength response due to asymmetric damage. A residual strength index calculation showed that the reduction was larger for the FEA than for the Smith method. A procedure is proposed that combines results of a few FEAs with the advantages of the Smith method to generate accurate biaxial bending load interaction curves for different ship conditions.