Structural Safety Analyses for Offshore Platforms Under Explosion Loadings

Abstract

A gas explosion in an offshore platform may result in loss of life, pollution, and critical damage to facilities. Safety critical structural elements of these facilities have to be designed to withstand high explosion loads. The present study discusses methodologies for explosion risk assessment (ERA) of safety critical structural elements and introduces a coupled Eulerian–Lagrangian (CEL) method to improve the accuracy of the dynamic structural response under explosion loading. The design accidental load is defined by explosion risk analyses in terms of drag pressure, differential pressure, and overpressure. In current practice, an explosion pressure-time history is simplified into a triangular shape and uniformly applied to the surface of the impacted structures. This approach cannot account for the interaction between elastic waves (normally solved by the Lagrangian method) in the structure and compression waves (normally solved by the Eulerian method) in air. The CEL method which accounts for fluid–structure interaction has been experimentally validated and leads to more realistic predictions of the dynamic response of structures when compared to other analysis methods. The plastic strains derived from the CEL analysis can be approximately 50% lower than those predicted by Lagrangian analysis. Therefore, significant potential weight reduction can be achieved using the CEL method for gas explosion analysis.