ABSTRACT

Marine structures are subjected to slamming loads characterised by high hydrodynamic pressure within short time durations. Such loads can cause local and global damages to structures. This paper, which is Part I in a series, reports a numerical investigation of slamming loads acting on flat stiffened plates and their dynamic response. The nonlinear explicit finite element code LS-Dyna with the Multi-Material Arbitrary Lagrangian-Eulerian (MMALE) solver was adopted to simulate the slamming impact on marine structures. The numerical method was validated by the relevant experimental data from the open literature in a comparison of slamming pressure and deflection data, as well as existing formulations. The Eulerian formulation was applied to describe the fluid flow, and a Lagrange formulation was employed to model flat stiffened plates. A penalty coupling algorithm was utilised to realise the fluid-structure interaction (FSI) between the plate and the fluid. Bilinear strain hardening with no strain-rate hardening and effect of the heat-affected zone (HAZ) were considered for the numerical simulation of the aluminum model, while nonlinear strain hardening and strain-rate hardening were adopted to verify the steel models. Effects of key influenced parameters such as water impact velocity, material behaviour, and air cushion on the slamming response were addressed accordingly. Additionally, a simulation of water hitting structure was proposed to investigate the slamming load characteristics acting on the bottom decks of offshore structures. As the next paper in this continuing series, Part II will present empirically derived formulations for prediction of slamming loads based on extensive parametric studies of actual scantlings of offshore structures, using the simulation methodology of water hitting proposed herein in Part I.

摘要

海洋结构在短时间内承受以高流体动力压力为特征的撞击载荷。这种载荷会对结构造成局部和整体损坏。本文是系列文章的第 I 部分，报告了对作用在平板加筋板上的砰击载荷及其动态响应的数值研究。采用带有多材料任意拉格朗日-欧拉（MMALE）求解器的非线性显式有限元程序LS-Dyna来模拟对海洋结构的撞击。数值方法通过来自公开文献的相关实验数据在砰击压力和挠度数据以及现有公式的比较中得到验证。欧拉公式用于描述流体流动，拉格朗日公式用于模拟平板加筋板。采用惩罚耦合算法实现板与流体之间的流固耦合（FSI）。铝模型的数值模拟考虑了无应变率硬化的双线性应变硬化和热影响区（HAZ）的影响，而采用非线性应变硬化和应变率硬化来验证钢模型。相应地解决了水冲击速度、材料行为和气垫等关键影响参数对砰击响应的影响。此外，提出了一种水撞击结构的模拟，以研究作用在海上结构底板上的砰击载荷特性。作为这个连续系列的下一篇论文，