A Fit-for-Purpose Framework for Post-Fire Structural Integrity Assessment of Steel Offshore Platforms

Fixed offshore steel platforms are vulnerable to hydrocarbon fires because of the continuous presence of combustible hydrocarbons during normal operations. Exposure to elevated temperatures can degrade the mechanical and metallurgical properties of structural steel, induce permanent deformation, damage protective coatings, and interact with pre-existing corrosion and section loss, thereby affecting both immediate structural capacity and continued-service durability. Existing fitness-for-service guidance and published methods address important components of post-fire assessment, including fire-damage screening, heat-exposure estimation, residual material behaviour, and thermo-mechanical structural response. However, these approaches do not individually provide an end-to-end offshore workflow linking post-incident field evidence with member-specific residual-condition assessment, structure-level reassessment, and reinstatement decisions. This paper presents a fit-for-purpose, code-complementary framework that integrates established assessment activities for the post-fire structural integrity evaluation of fixed offshore steel platforms. The framework comprises five sequential stages: post-fire in situ investigation; heat mapping and damage classification; assessment of residual material, corrosion, and section condition; structural integrity reassessment using updated material and section properties; and prioritization of repair, strengthening, and corrosion-protection reinstatement. The framework is demonstrated using a sample offshore fire case study in which post-fire material properties are incorporated into structural integrity analyses to identify members requiring intervention and assess the continued serviceability of unaffected components. The proposed framework provides a systematic interface between post-fire field evidence, material-condition assessment, structural analysis, and engineering-based decision-making. It is intended to support evidence-based, member-specific fitness-for-service decisions, fit-for-purpose structural repair and/or replacement, and support the safe reinstatement and continued in-service of fire-damaged offshore steel structures.