Non-linear long duration blast loading of cylindrical shell structures

This paper investigates the influence of long-duration blast loads on the structural response of aluminium cylindrical shell structures. Full scale coupled non-linear dynamics are examined experimentally at one of the worlds’ most powerful air blast testing facilities. Evaluating structural response to blast loads of this magnitude is exceptionally difficult using only computational fluid dynamics; typically not achievable without incurring unmanageable solution domains. Clearing, diffraction and exhaust of a long-duration blast wave across any comparatively small structure imposes constraints leading to the use of approximated drag coefficients, designed primarily to expedite the calculation of net translational forces. In this research, detailed pressure histories measured experimentally on the surface of the cylindrical shell are used to accurately configure a computational analysis dispensing with the requirement to utilise approximated drag forces. When further combined with accurate material test data, fibre optic controlled strain gauge instrumentation and high-speed video photography, a full comparative model was possible. This paper shows that without exact knowledge of long-duration flow-field effects a priori, it is very difficult to reliably determine the mode of structural response and degree of blast resistance. Preliminary modelling predicted a global sway and localised plate buckling; however, subsequent experimental testing showed a crushing failure of the shell before any translational movement occurred. Results in this paper will be of direct interest to both practitioners and researchers considering the dynamic response of cylindrical shell structures subject to high power explosive blasts from sources such as hydrocarbon vapour cloud ignition.