A supply ship, the PSV Monarch, was involved in a collision with legs 1 and 4 of the Granite Point platform located in the Cook Inlet, Alaska. Due to damage to the ship incurred during the impact, the ship eventually took on water and sank. The incident occurred at flood tide levels and under heavy ice conditions. This was regarded as a collision incident involving significant forces. Consequently, the structural integrity of the platform was an immediate concern.
Analyses were performed to verify that the structural integrity of the Granite Point platform was not adversely affected. Hand calculations determining the impact forces were created based upon energy equations and the current speeds in the inlet. Then two analyses were performed using an ANSYS model of the jacket structure; a linear static analysis with the ice and impact forces applied, and a transient analysis with the ship mass impacting the platform at the speed of the current. The results of both analyses were reviewed, and it was determined that the likelihood of any adverse structural damage to the offshore platform jacket structure was minimal.