| dc.description.abstract | In 2017 the NORSOK N-003 code action and action effects was revised regarding energy requirements
for ship collision with offshore installations. Previous energy requirements for ship collision with an
offshore installation were set to be 11 MJ and 14 MJ for head-on/stern and broadside. Now the revised
version allows for 50 MJ impact for all events. This stems from advancements in ship design over the
past decades, which have introduced larger supply vessels and bows such as bulbous bows and X-bow.
This study inquires into ship collision with a semi-submersible offshore platform with the revised energy.
Simulated collision events include bow, stern and broadside for bulbous bow and X-bow. The platform
column and vessel are modelled to simulate the collision interaction for the various events. The vessel
represents a 10 000 tonnes offshore service vessel including added mass during impact and impact velocity
is set to achieve an impact energy of 50 MJ. A Non-Linear Finite Element Analysis (NLFEA) is conducted
and numerical results are discussed herein. The results primarily focus on the penetration and deformation
of the semi-submersible platform that causes flooding of compartments. Where a strain-based failure
criterion is applied to represent the failure of the elements. The analysis focuses on a shared energy
design using mean material properties for both ship and platform with no added safety factors. Findings
from the analysis suggest that the impact location greatly affects the number of penetrated compartments.
As well as increased energy does not satisfy the original acceptance criteria which allow for 2 penetrated
compartments. Results also suggest that low-energy collision does not distinguish bulbous bow or X-bow
as more critical in terms of damage to the platform. However, large energy impacts indicate that X-bow
collisions have a greater damage potential than the bulbous bow. Penetration of compartments has a
close relation to the fracture of the platform shell. This study has applied the simplest representation
as strain-based criteria. More advanced criteria such as strain-dependent failure criteria would more
accurately represent the fracture of elements. | |