Transient loading and dynamic response of structures due to pressure waves and deflagration

Abstract

Accidental deflagration of gas clouds poses a persisting safety risk in industries handling flammable substances. Today, the assessment of structures against accidental loads is an integral part of the design process of modules in, among others, the oil&gas industry. Simplified models to estimate structural loading and response to deflagration incidents are yet scarce, and are mostly extrapolated from models developed for military applications. In this thesis various aspects of the effects of deflagration waves on structures are investigated, and predictive analytical models for the loading and structural response of structures are developed. First, the influence of fluid-structure interaction on pressure wave loading is analysed. Using a combined analytical and numerical approach, the effect is quantified and results are synthesized in the form of non-dimensional maps covering a wide range of possible scenarios. It was found that fluid-structure interaction only plays a minor role in the loading of typical structures by pressure waves in air. The loading of structures by pressure waves is then further examined for the case of a box-like object. Detailed computational fluid dynamics simulations are conducted to produce non-dimensional design maps providing load amplitudes for a wide range of scenarios. An analytical model has been developed which is capable of predicting the transient load history on a box-like object. Different loading regimes have been identified. Finally, a novel analytical model to predict the elastic-plastic response of clamped metallic beams to transverse pressure loading has been developed. This model formulates a scheme of interconnected response phases of a beam, including the effects of elastic flexural waves, plastic hinges, plastic shear sliding, and large deformations. The model was found in excellent agreement with detailed finite element simulations. Non-dimensional design maps are constructed which predict maximum beam deflections and the amount of plastic deformation for a wide range of beam thicknesses and loading parameters.