Structural safety assessment was performed for the collision and grounding scenarios of specialized ship and its cargo. To ensure reasonable and reliable safety assessment, realistic full-scale ship collision and grounding simulations were carried out, using FSI analysis technique of LS-DYNA code and propulsion force instead of velocity in simulations.
There was no fracture damage in the side inner side hull of DWT 2,600 ton specialized ship as struck ship, except DWT 35,000 ton striking ship in ballast condition to struck one in service at 90 and 80 degree attack angles, and also no damage in the inner bottom hull of specialized ship as grounding one, even rock height 0.75m above inner bottom hull under full load condition.
Contrary to the void condition simulations, more realistic collision and grounding response behaviors could be found in the surrounding sea water, in that striking ship moved laterally before collision, and a lot of kinetic energy of large size of striking ship might be transferred to the fluid energy, which would give a reasonable collision speed response after collision in addition to the loss of internal energy to the struck ship. Realistic grounding response behaviors of the grounding ship was also observed, such as jumping and sway around the rock under its self weight, depending on its load condition, rock height and position.
Through the full-scale collision simulation of cargo container boxes and drums loaded inside the cargo hold of struck ship using FSI analysis technique, it was found that their crashworthiness capacities and damage patterns could be relatively well figured out with their energy dissipations, and their structural safeties would be assessed with high reliability. Container boxes and drums in shell guide also contributed greatly to the crashworthiness of side structure of struck ship, and no damage occurred in the drums, except damage only in the bottom and side of square concrete drum with no damage in its inside even in the very serious collision scenario.
It could be confirmed that this specialized ship might be superior to the severe collision scenarios due to the wide double side hull space. In the future study, some verification works on the collision and grounding simulations should be performed for the enhancement of their reliability, using FSI analysis technique.