Energy absorbing passive impact barrier for profiled blastwalls

After the Piper Alpha accident, the Health and Safety Executive (UK) now require safety cases to be submitted for all new and existing installations on offshore topsides. The findings from a recent Joint Industry Project have revealed that peak overpressures developed from typical hydrocarbon explosions can be much higher than previously used in the design of offshore topsides and thus has necessitated strengthening of many existing installations, including blastwalls. This paper presents one such technique where the response of the blastwalls is modified by the inclusion of a passive impact barrier system placed at a certain offset behind the walls. An explicit non-linear finite element model has been validated against two large scale blast tests of shallow profiled blastwalls. This has included modelling the effect of contact, weld tearing, large displacement and plasticity in order to provide a realistic model. The study has been extended to investigate the response of deep profiled blastwalls with various arrangements of the passive impact barrier systems. The increase in the containment pressure and the influence of strain rate, load duration, offset of the impact barriers and its stiffness are discussed.