IG Cullis. Blast Waves and How They Interact With Structures.

The paper defines and describes blast waves, their interaction with a structure and its subsequent response. Explosions generate blast waves, which need not be due to explosives. A blast wave consists of two parts: a shock wave and a blast wind. The paper explains how shock waves are formed and their basic properties.The physics of blast waves is non-linear and therefore non-intuitive. To understand how an explosion generates a blast wave a numerical modelling computer code, called a hydrocode has to be employed. This is briefly explained and the cAst Eulerian hydrocode is used to illustrate the formation and propagation of the blast wave generated by a 1 kg sphere of TNT explosive detonated 1 m above the ground. The paper concludes with a discussion of the response of a structure to a blast wave and shows that this response is governed by the structures natural frequency of vibration compared to the duration of the blast wave.The basic concepts introduced are illustrated in a second simulation that introduces two structures into the blast field of theTNT charge. Introduction In both the military and civilian worlds, blast waves and their interactions with a structure need to be understood. Explosions form blast waves. These explosions can be either deliberate or accidental. Deliberate explosions can include demolition charges, weapon systems and improvised explosive devices. Accidental explosions can result from the ignition of gas clouds and inflammable liquids and chemicals due to fire or the failure of pressurised containers. In all cases the effects of the blast waves produced need to be quantified, particularly in respect of injuries to personnel. A blast wave is formed by a sudden release of energy.The source of the energy release is not important. However, for many materials, particularly explosives, the very high rate of the energy release generates a tremendous power source. It is this power source that is responsible for the catastrophic damage often associated with an explosive. The generation, development and propagation of blast waves are governed by the non-linear* physics that describes shock waves. In the case of an explosive, its’ detonation properties define the properties of the blast wave. In the military scenario, blast waves created by explosive charges are the major concern. In this paper, therefore, the detonation of 1kg of TNT is used to illustrate the main features of a blast wave interacting with structures – the ground and