With growing traffic and higher vessel speed in the sea, the risk of ship collision accidents is continuously increasing. Ship collisions are structural impact accidents between e.g. ship and ship or ship and offshore installation. The consequences of ship collisions include:
- Loss of human life.
- The environmental impact of oil spills, especially where large tanker ships or offshore platforms are involved.
- Financial consequences to local communities close to the accident.
- Financial consequences to ship owners, due to ship loss or penalties.
- Damage to coastal or offshore infrastructure, for example during a collision with a bridge or an offshore platform.
Boat impact with offshore installation is characterised by low impact velocities and high impact energy because of the large mass of the vessel. Local damage in the impact area is usually substantial, and the global response of the structure may be significant. In the interest of safety and economy it is essential that the analysis
is accurate and takes full account of the energy absorption capacity of the actual structure. The boat impact hazard has been controlled in several offshore development projects by weight optimum design modifications reducing boat impact hazard to acceptable minimum.
Typical scope of work for boat impact consequence assessment includes:
- Based on probabilistic or deterministic methods define impact energy of the impacting ship. Establish geometry and strength characteristics of impacting ship. Establish acceptance criteria for damage.
- Develop nonlinear computer model of the ship and structures subjected to impact.
- Perform nonlinear strength analysis to assess impact force and energy absorption in the structure and the ship as a function of displacement. Normally USFOS is applied for JACKET (beam) structures and LS-DYNA for GBS and FLOATING (shell) structures.
- Based on the force- and energy results from analysis, identify the critical impact energy (velocity and mass) for a selected level of energy absorption in the vessel.
- If necessary, perform non-linear dynamic strength analysis using LS-DYNA to establish the true response in the time domain to the actual impact.
Deliverables – Technical Report documenting:
- Impact force and absorbed energy in the structure (and in the vessel if modelled) as a function of deflection of the impact area.
- Maximum and permanent deformations and stresses in the structure around the impact area.
- Plastic strains or crack propagation in the damaged structures.