A detailed comparison of different corrosion addition models on ultimate strength of product tankers

Abstract

Abstract

The ultimate bending moment capacities of a product tanker's hull girder under sagging and hogging conditions are evaluated by Nonlinear Finite Element Method considering different scantlings for the tanker. Different scantlings are resulted from different corrosion additions added to the net scantlings of the ship. Fourteen cases of structural scantlings are accounted for, which cover the corrosion additions defined by Common Structural Rules (CSR) of International Association of Classification Societies (IACS), the corrosion additions of a classification society before the introduction of CSR and corrosion additions calculated from two academic models called as the exponential and the linear models herein. According to the analyses of this study, the exponential, average linear and Pre-CSR models result in close ultimate strength values, while the results for the cases of corrosion additions defined by IACS, are much higher and resemble to the results of severe linear models. IACS corrosion additions increase the ultimate bending moment of net-scantlings design by 47% in sagging condition and by 36% in hogging condition. In case of academic models, that increase is 18% and 14%-to-18% for sagging and hogging conditions, respectively. Results obtained from the cross-sectional properties' calculations and ultimate strength analyses in this study; reveal that the corrosion model presented by IACS corresponds to a severe level of corrosion. The corrosion additions defined by IACS is found to be approximately twice the average values of corrosion depth for structural members at the end of a 25-year design life and even more than that.