Practical Formula for Predicting the Residual Deflection Evolution of Steel Plates Subjected to Repeated Impacts

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.