Ultimate strength of aged ships under hull structure’s imperfections

Abstract

Ship hull structures, particularly those with extended service life, contain various imperfections, including initial deformities, residual stresses, and corrosion-induced degradation. Such variables critically influence the structural integrity of the hull girder. Consequently, comprehending the residual strength capacity of the hull girder is paramount for guaranteeing the vessel’s operational safety and dependability, especially under severe loading scenarios. The existing methods to determine the hull girder’s ultimate bending moment either ignore imperfections or consider imperfections such as initial deformations or residual stresses but with the assumption of a fixed level. In the current study, the stress distribution method and incremental-iterative method are used; and solutions are proposed to cover factors such as initial deformations, residual stresses, and corrosion. A single skin bulk carrier, 56,000 DWT of deadweight, is employed as the demonstrative example. Eleven cases of imperfections are suggested, and the variations of ultimate bending moment for hogging and sagging conditions under the effect of uncertainties are analyzed and evaluated. The results of the current study are offered and discussed. Several concluding remarks are also presented.