Little guidance is available in the public domain for the design of the profiled blastwalls commonly used in offshore structures to resist accidental explosions. The provision of the Technical Note 5 (TN5) has helped to bridge some of the gaps and it deals mainly with the Single Degree of Freedom method (SDOF) to obtain the dynamic response of the blastwalls. The adequacy of the design guide is assessed by comparison with numerical nonlinear finite element models for three profiled sections with different degree of compactness. The static capacity and the dynamic response of the blast walls are established up to their maximum capacity level and into the post peak or buckling response regime. Effects of cross section flattening, local transverse effects, support rotation and the effects of cross section compactness on the overall behaviour of the blast barriers are discussed.


The provision of adequate blast resistant barriers is an integral part of the design of an offshore topside structure where they are required to protect personnel and safety critical systems from the consequences of an explosion and subsequent fire. Blast barriers under extreme loading levels are likely to involve large plastic deformation, weld tearing and possible contact with adjacent plant or structural components. Pre-Piper Alpha designs of existing barriers only consider low blast pressures on the order of 0.1 – 0.3 bar. Depending on the profiles and grade of the barriers, the response at this level is likely to be in the elastic regime. However, a recent joint industry project in blast and fire engineering for topside structures (Selby and Burgan, 1998) which has addressed key issues relating to the characteristics of offshore hydrocarbon explosion have shown overpressures of several bar are possible in a typical offshore topside module.

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