This paper presents a procedure for evaluating the collision response of fixed offshore structures exposed to high energy collisions with Offshore Service Vessels (OSV) or other floating units. A combination of traditional non-linear frame analyses for screening purposes and more detailed non-linear FE analyses using an explicit code is proposed. In the detailed integrated FE analyses, both the fixed offshore structure and the impacting vessel are explicitly modeled as deformable bodies. The progressive changes in contact and the resistance of both deforming objects are fully accounted for, enabling for more accurate results compared to methods where the resistances of the two objects are assessed separately. Results from case studies are shown. The calculated resistances for the striking objects are compared to the load-indentation curves presented in DNV-RP-C204 [1] and NORSOK N-004 [2].