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This study compares the Residual ultimate longitudinal strength – grounding Damage index (R-D) diagrams produced by two analysis methods: the ALPS/HULL Intelligent Supersize Finite Element Method (ISFEM) and the design formula (modified Paik and Mansour) method – used to assess the safety of damaged ships. The comparison includes four types of double-hull oil tankers: Panamax, Aframax, Suezmax and VLCC. The R-D diagrams were calculated for a series of 50 grounding scenarios. The diagrams were efficiently sampled using the Latin Hypercube Sampling (LHS) technique and comprehensively analysed based on ship size. Finally, the two methods were compared by statistically analysing the differences between their grounding damage indices and ultimate longitudinal strength predictions. The findings provide a useful example of how to apply the ultimate longitudinal strength analysis method to grounded ships.

Considerable efforts have been devoted to developing rapid methodologies for predicting the residual strength of ship hull girders for a given damage scenario (e.g., R–D diagram). This task is usually challenged by the difficulty of a proper definition of damaged scenarios, which is a function of the damage location and extent. The concept of damage index (DI) was proposed to resolve this issue, and its application has been demonstrated previously through the incorporation of the Intelligent Supersize Finite Element Method (ISFEM) and Modified Paik–Mansour (P–M) approach. Alternatively, a Smith-type progressive collapse can be adopted. In fact, this may enable a more comprehensive application of the DI concept, as the Smith-type approach is codified in the Common Structural Rule (CSR) for assessing the longitudinal strength of the hull girder. In light of this, the damage index based assessment tools (i.e., R–D diagram) incorporated with a Smith-type progressive collapse method is presented in this paper. This also facilitates a comparison with the R–D diagram previously developed by ISFEM and Modified P–M approach. Discussion is given regarding the discrepancy between different methods, and recommendations for future research are outlined. • Damage index (DI) based condition assessment of grounded hull girders. • Residual strength versus damage index diagram is developed for the first time by a Smith-type method. • Comparison is presented for R-D diagram based on ISFEM, Modified P-M method and Smith method. [ABSTRACT FROM AUTHOR]