Risk-based Structural Response Against Explosion Blast Loads: Systematic One-to-one CFD (flacs) / Nlfea (impetus Afea Solver) Coupling to Derive Quantified Response Exceedance

Abstract

This paper proposes an advanced and innovative methodology for risk-based structural response assessment against accidental explosions. Focus is shifted from dimensioning load to barrier integrity. A full spatial mapping of blast overpressure transients obtained with Computational Fluid Dynamics (CFD) modelling is used in combination with a Non-Linear Finite Element model (NLFEA). The GexCon-Impetus methodology is so-called advanced due to the innovative extensive one-to-one CFD-NLFEA job solution scheme used over several explosion runs. Using a detailed explosion loads mapping for the response evaluations provides a comprehensive probabilistic description of the response characteristics, easy to combine with risk acceptance criteria and performance requirements. The 3D codes involved are FLACS (CFD) and IMPETUS Afea solver (NLFEA). The response of an offshore fire partition wall is specifically studied against dynamic explosion loads. Detailed modeling of the wall is made in IMPETUS Afea solver. Systematic direct coupling between 90 FLACS risk-based explosion simulations and 90 IMPETUS Afea dynamic response calculations is used. The safety barrier performance is quantified using adequate wall response parameters reported for every explosions. The innovative outcome is a probabilistic picture of the response parameters exceedance. The barrier ability to perform the related safety function(s) is efficiently documented. Of utmost importance, mechanisms that cause possible lack of integrity are highlighted. The results are compared with existing offshore approaches based on the Dimensioning Accidental Load (DAL) concept. A uniform triangular loading and a realistic dimensioning explosion are used. Promoting more consideration of adequate response assessment as part of the safety studies, the paper shows how the advanced method pinpoints limitations of conventional approaches. For the risk owner, it improves the comprehension and implications upon the relation between explosion loads and their consequences on structures carrying critical safety functions. Several benefits result from the GexCon-Impetus approach among which: a more accurate streamlined workflow, an improved understanding of the safety barrier behavior, perception of safety margins, justifications for design optimization, cost & weight savings.