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Abstract Closed-form expressions to estimate the energy absorption and damage extent for severe ship collision damages were initially developed in 1999 [1, 2], and further validated with experimental data in 2016 [3]. To gain further confidence for applications within design using the proposed analytical procedure, it is evident that more detailed and comprehensive comparisons and validations with experiments and numerical simulations are necessary. The purpose of the present paper is to use the analytical approach and finite element analyses to study in depth model-scale and full-scale collision tests so that to further quantify key calculation parameters and to verify the capability and accuracy of the proposed analytical method. In total 18 experimental tests and one full-scale collision accident are evaluated. The 18 experimental energy absorption-penetration and collision force-penetration curves, and the associated finite element simulations, are compared with results obtained from the analytical calculations. It can be concluded that the analytical method gives consistently good agreement with all experiments analysed here. Finally, an application of the analytical method is demonstrated by an example where speed restrictions are determined in a port to avoid LNG cargo leakage in an event of an LNG carrier being struck by another ship. Highlights • An analytical method for ship collision damage assessments is validated with 18 experiments and one full-scale collision accident data. • It is demonstrated that a consistent good agreement with the experiments is achieved when using a common criterion for the assessment. • Comparisons of energy-penetration and collision force-penetration curves between the experimental results, the analytical calculations and the finite element simulations are also provided. • An application example for managing collision risks at busy ports to avoid potential cargo leakage in an event of an LNG carrier struck by other ships is demonstrated. [ABSTRACT FROM AUTHOR]

The paper compares two methods based on finite element simulations to assess the external dynamics and the internal mechanics in ship collisions. One method treats independently the external dynamics and the internal mechanics (decoupled method), while the other one couples their interaction (coupled method). In the decoupled method, the external dynamics are evaluated by the analytical approach of Pedersen and Zhang (1998), and the internal mechanics are assessed by simulations performed with the LS-DYNA finite element solver. In the coupled method, both the external dynamics and the internal mechanics are evaluated directly by numerical simulations that follow the model of Pill and Tabri (2011). The two methods are compared to determine the differences in predicting the deformation and rupture of the collided ship structures and to assess the relationship between the structural deformation energy of the struck ship and the energy loss of the striking ship. The objective of the paper is to verify whether the decoupled method satisfies the predictions required for design appraisal assessments. The paper also illustrates the influence of the collision angle on the mechanics of ship collisions. [ABSTRACT FROM AUTHOR]

The paper is dedicated to enhance the industry practice in collision simulations of ship structures when only limited time and material data are available. The idea is to establish a simple, but effective procedure to determine the ‘critical failure strain’ as a function of coarse mesh sizes, so as to predict the critical energy to be absorbed during the impact. For this reason, more complicated effects, such as strain-state dependence, strain concentration on the lateral stiffening, welding, as well as accurate deformation mechanisms, are omitted. A new expression is introduced to estimate the failure strain of coarse meshed ship structures struck by an indenter with hemispherical shape where the ship side or bottom sustains local penetration during a bulbous bow collision or stranding. The expression is valid for mild and high strength steels, accounts for the size of the elements, and is derived from finite element simulations of coarse meshed plates punched until the onset of necking, which critical point is first determined by using fine meshed plates. This ‘simple’ criterion is validated against reported experiments of 3 stiffened plates and 6 double-hull structures quasi-statically punched by an indenter. For the 6 double-hull specimens evaluated here, the absorbed energy at the end of the impact event is predicted with sufficient accuracy when a coarse mesh of size 10 times the plate thickness is used (the difference is about 10%). [ABSTRACT FROM AUTHOR]

Closed-form analytical solutions for the energy released for deforming and crushing of structures and the impact impulse during ship collisions were developed and published in Marine Structures in 1998 [1]. The proposed mathematical models have been used by many engineers and researchers although the methods were only validated with time domain numerical simulation results at that time. Since then, model and full-scale measurements have been carried out and experimental results are available in the public domain. The purpose of the present paper is to use such experimental results to further analyze the validity and robustness of the closed-form analytical methods as well as to further improve some parameter's accuracy. In total, 60 experimental results have been analyzed and compared with the analytical results and this paper presents the outcome. It can be concluded that the analytical methods give a reasonable agreement with the experimental results. The paper also introduces a simple concept to account for the effective mass of liquids with free surface carried on board of a ship and it is shown how the analytical analysis procedure can be expanded to take into account the effect of ship roll on the energy released for crushing. [ABSTRACT FROM AUTHOR]

The paper presents a simplified analytical method to examine the energy absorbing mechanisms of small-scale stiffened plate specimens, quasi-statically punched at the mid-span by a rigid indenter with a knife or a flat edge shape. To validate this method, experiments and numerical simulations are conducted on specimens scaled from a tanker side panel limited by one span between the web frames and the stringers. Therefore, the paper provides practical information to estimate the extent of structural damage within ship side panels during collision accidents. The experimentally obtained force–displacement responses and shapes of the deformation show good agreement with the simulations performed by the explicit LS-DYNA finite element solver. The numerical results manage to describe the process of initiation and propagation of the material fracture in the side panel specimens and provide detailed information of the energy dissipated by each structural component and its contribution to total energy during the entire deformation process. The analytical method derives expressions to estimate the relation between the plastic deformation and the energy dissipation of the stiffened plates. Both the plate and the stiffener elements dissipate the energy through rotation of the plastic hinges at the applied load and the support and the membrane tension over the plastically deformed region between the loading and the supports. The proposed simplified expressions give a good agreement with the experimental and numerical results. [ABSTRACT FROM AUTHOR]