The objective of this study is to develop a new formulation for predicting the permanent local denting damage of steel ring and/or stringer-stiffened cylinders under dynamic lateral mass impact. The considered scenarios could represent the collisions of offshore cylindrical structures with bow or stern of service vessels or floating objects. Before deriving the formulations, the numerical methods were developed using ABAQUS/Explicit to determine the deformation of these stiffened cylinder structures subjected to dynamic lateral mass impact. Next, rigorous parametric studies were performed on the actual design full-scaled stiffened cylinder examples using the developed numerical method. Based on the rigorous numerical results, new simple design formulations to predict the maximum permanent local dent depth of a stiffened cylinder are derived through a regression study as the function of a non-dimensional energy parameter. The accuracy and reliability of the derived formulations are confirmed by comparison with the available test results, nonlinear FEA and existing analytical, and empirical equations in the literature. A good agreement with existing test data for ship-offshore structure collisions was achieved.

Offshore structures and ships can be progressively damaged due to repeated mass impacts induced by contacts with ships, ice floes, and dropped and/or floating other objects while in service. This paper aims to predict the residual deflection evolution of the marine structures under such impact repetitions. The side hull structures of the general ice-class vessels were selected for this study. The numerical simulations were performed to predict the deflection response of repeatedly impacted stiffened plates by using the software package Abaqus 6.13. For the simulations, the strain hardening of the relevant ice-class steel grade was adopted using the proposed constitutive equations, and the strain-rate hardening effects were taken into account by employing the existing formulations. The developed numerical model was substantiated against tests available in the open literature. Based on the validated model, a parametric study on various stiffened plates was performed. The evolution of the residual deflection of the repeatedly impacted plates with actual scantlings and various impact scenarios was investigated. A practical formula for the prediction of the residual deflection evolution of the plates under repeated mass impacts was proposed based on the regression analysis of the parametric study results. The reliability and accuracy of the proposed formula were confirmed through comparisons with numerical simulations and existing analytical formulations. It is expected that the proposed formula can be efficiently employed as a quick-hand tool for the reliable prediction of the residual deflection evolution incurred by repeated mass impacts.

This paper presents an investigation of the scale effect on the flow around a propeller using the CFD method. The differences in the numerical setup and the results obtained for the characteristics of an open water propeller are described and analysed in this paper. Moreover, the paper also highlight and analyse the scale effect on differences in flow around the propeller, such as the pressure fields in the cross section, the distributions of the skin friction coefficient and limiting streamlines on the propeller blade, the vortices in the wake of the propeller, and the velocity fields. The differences in the flow around the propeller are more clearly seen when it works under heavy loading conditions, an important finding that can support designers in improving propeller performance, investigating cavitations, etc. at the full scale. The reference propeller used in this study is the benchmark propeller PPTC VP 1304.

This study aims to develop new formulations for predicting the permanent local denting damage of steel stiffened cylinders under dynamic lateral mass impact and their residual strength under combined loads. The considered scenarios could represent the collisions of offshore cylindrical structures with bow or stern of service vessels or floating objects. For this, two types of the stiffened cylinders, namely, stringer- and/or ring-stiffened cylinders, are generally main components of offshore marine structures used in semi-submersibles, submarines, tension legs of platforms (TLPs), and other various types of floating offshore structure are investigated. Before deriving the formulations, the numerical methods are developed using ABAQUS/Explicit to determine the deformation of these stiffened cylinder structures subjected to dynamic lateral mass impact. Next, rigorous parametric studies were performed on the actual design of full-scaled stiffened cylinder examples using the developed numerical method. Based on the rigorous numerical results, new simple design formulations to predict the maximum permanent local dent depth of a stiffened cylinder are derived through a regression study as the function of a non-dimensional energy parameter. Additionally, new simple design equations, which are used to predict the ultimate residual strength of the dented stiffened cylinders under combined loads are also proposed. The accuracy and reliability of the derived formulations are confirmed by comparing with the available test results, nonlinear FEA, and existing analytical and empirical equations in the literature. A good agreement with existing test data for ship-offshore structure collisions was achieved.