Hazard Propagation I: Explosions and Blast

Abstract

The chapter gives a broad overview of the hazard source definition and the hazard potential propagation. Explosions, in particular detonations are the sample hazard type, which is also used in later chapters for the illustration of further steps of risk management and analysis. The chapter shows that even for understanding the hazard potential of a single type of threat, a multitude of effects have to be considered for sufficient analysis. The classical categorization of explosions is extended allowing for malicious (terroristic) explosions, e.g. car bombs. Such events are defined with respect to existing categories of explosions. It is motivated why it is benefitial to distinguish between the description of the local hazard source and the (potentially non-local) hazard potential (field) due to the hazard propagation (if any) in case of a threat event. A schematic overview is given which hazards are generated by explosions and how they propagate, in particular fragments, debris and fire ball. For high explosions (detonations), the hazard propagation of blast (shock wave in air) is described for the near and far field. In particular, the parameters are given that describe the hazard potential for most applications: specific blast impulse and overpressure. In a similar way, for other applications local hazard fields can be described. Several scaling laws for explosions are introduced. Their importance is that they can be used to scale experimental tests for scenario assessment and when carefully employed also for validation of computational approaches. It is an illustrative exercise to exemplarily model the damage effects due to pressure loadings using a simplified single degree of freedom model. It shows that the dynamic static and quasistatic response of structures due to blast loading is rather different when compared to the empirically much more accessible static loading of structures.