Hervé Le Sourne

Numerical crashworthiness analysis of an offshore wind turbine monopile impacted by a ship

The objective of the present work is to understand the crushing behavior of a predefined wind turbine jacket when it is impacted by a ship. To investigate the resulting deformation modes and the repartition of dissipated energy, nonlinear finite element analyses are performed to simulate both rigid and deformable ships colliding the jacket at different velocities. In a first part, a sensitivity analysis to the jacket impacted area is carried out to find the most damaging situation. Then, the influences of gravity loads, wind force, and soil stiffness are studied, considering that the striking ship is rigid. In a second part, the jacket is supposed to be collided by two different deformable vessels and the internal energy distribution between the jacket and the striking ships is analyzed for different jacket leg thicknesses. Some numerical analyses focus also on the transfer of the crushing force between the impacted leg to the others through the braces. All these numerical results will further serve to fix the hypotheses for the development of a simplified tool based on analytical formulations.

Simplified Analytical Method for Estimating the Resistance of Lock Gates to Ship Impacts

The present paper is concerned with the design of lock gates submitted to ship impacts. In this paper, a simplified analytical method is presented to evaluate the resistance of such structures under collision. The basic idea is to assume that the resistance is first provided through a local deforming mode, corresponding to a localized crushing of some impacted structural elements. For consecutive larger deformations, the resistance is then mostly provided through a global deforming mode, corresponding to an overall movement of the entire gate. For assessing the resistance in the case of the local deforming mode, the structure is divided into a given number of large structural entities called “superelements.” For each of them, a relation between the resistance of the gate and the penetration of the striking ship is established. However, as some results are already available in the literature, this subject is not treated extensively in this paper. On the contrary, the calculation of the resistance of the gate provided through the global mode is detailed and the strategy to switch from local to global deformation is highlighted. Finally, we propose to validate our developments by making a comparison between results obtained numerically and those predicted by the present analytical approach.

A Ship Collision Analysis Program Based on Upper Bound Solutions and Coupled with a Large Rotational Ship Movement Analysis Tool

This paper presents a user-friendly rapid prediction tool of damage to struck and striking vessels in a ship collision event. To do this, the so-called upper bound theorem is applied to calculate internal forces and energies of any substructure involved in the ships crushing process. At each increment of indentation, the total crushing force is transmitted to the external dynamics MCOL program, which calculates the global ship motion correction by solving the hydrodynamic force equilibrium equations. As a first step, the paper gives a brief description of the upper bound method originally developed for perpendicular collisions and recently enhanced for oblique ones. Then, the theory developed in MCOL program for large rotational ship movements is detailed. By comparing results obtained with and without MCOL, the importance of hydrodynamic effects is highlighted. Some simulation results are compared with results provided by classical nonlinear finite element calculations. Finally, by using the developed analytical tool, which mixes internal and external dynamics, different crushing scenarios including oblique collisions are investigated and the influence of some collision parameters like longitudinal and vertical impact location, impact angle, and struck ship velocity is studied.

Fast strength assessment of mitre gates to ship impact

The present paper is concerned with the design of lock mitre gates submitted to ship impacts. A simplified analytical method is presented to evaluate the resistance of such structures under collision. The basic idea is to assume that the resistance is first provided through a local deforming mode, corresponding to a localised crushing of some impacted structural elements. For consecutive larger deformations, the resistance is then mostly provided through a global deforming mode corresponding to an overall movement of the entire gate. The developments are validated by comparing results obtained numerically to those predicted by the developed analytical approach for mitre gates.

A Simplified Procedure to Assess the Strength of a Ship Impacting a Lock Mitered Gate

This paper presents a simplified procedure allowing for a rapid prediction of the strength of a lock mitered gate s ubmitted to a ship impact. In this article, the force opposed to the penetration of the vessel is derived by supposing that the bow is perfectly rigid, so the total initial kinetic energy has to b e entirely transformed through an internal dissipation. For a given penetration of the striking vessel, an analytical p rocedure is followed in order to estimate the amount of energy dissipated by local and global deformations of the impacted st ructure. An equivalent quasi-static force is then derived. A co mparison is made with a finite elements simulation in order to test the analytical procedure.