In order to ensure the structural integrity of an offshore platfonn when Subjected to explosion loading, the strength of the blast walls has been investigated. Since previous studies using implicit finite element codes have indicated that the walls will fail when subjected to a static load equivalent to the maximum overpressure due to the explosion, the dynamic response of the structure has been investigated using an explicit finite element code, PAM-CRASH. Dynamic effects such as the inertia of the structural members, strain rate hardening of the steel and energy absorbed by plastic deformation, which are not accounted for in an implicit analysis, are included and are demonstrated to be of significant importance. The effect of the proposed structural modifications to the protective walls, including the application of high modulus carbon fibre bonded to the support beams has been investigated numerically. A method has been formulated to compute the structural dynamics by coupling a detailed model for the part of the structure expected to undergo the strongest structural deformation, to an existing ASAS-H analysis model for the remaining part of the structure. The computational results and an assessment of the protective walls including the composite reinforcement will be subjected to blast loading during a large scale test. The results from the tests will be used to validate the application of the PAM-CRASH program to the analysis of the structure. Using this approach it was not necessary to prolong the annual shutdown on the platform whilst major modification work was performed to the blast walls.
The evaluation of safety issues on offshore platforms has been of increasing importance since the publication of the report on the Piper Alpha Disaster which prompted legislation requiring operators to produce a formal safety case for each of their installations in the UK North Sea.
