The structural integrity assessment of offshore topside structures focuses on protecting pressurized hydrocarbon piping and vessels from damage and fracture, and providing safe escaping routes for the personnel for a specific amount of time. In order to achieve these goals, it is critical to apply a sufficient quantity of Passive Fire Protection (PFP) on the topside structure steel members. On the other hand, excessive use of PFP on the structure results in considerable additional cost and extra added dead load to the structure. The main objective of this paper is to demonstrate that by employing finite element analysis (FEA) which accounts for material and geometric nonlinearities as well as load re-distribution, PFP application can be optimized.
Simplified and conservative approaches are available to estimate the extent and amount of the PFP on the offshore structures. However, the main concern with simplified approaches is that they can lead to over-application of the PFP resulting in substantial increase in the topsides weight. With the use of advanced engineering analysis and knowledge of critical load paths, an optimized PFP scheme can be developed that would maintain the structural integrity of the structure and also provide sufficient escape time for personnel during fire. Ductility level analysis will be used to demonstrate that by using proper heat transfer simulation and FEA, amount of PFP application can be optimized. Detailed analysis will be carried out using general-purpose finite element software package. Temperature dependent thermal and mechanical material properties will be taken into account in the analysis. Methodology and analysis of the results of PFP optimization will be discussed in this paper.