Characterization of debris throw from masonry wall sections subjected to blast

The failure of structural components, e.g. masonry walls, due to accidental or intentional explosions exhibits a considerable risk to the health of persons, operational safety, and surrounding structures. The debris throw originating from overloaded structural elements poses a significant threat to structures and persons in the surrounding environment in distances, which may exceed the hazard-range of the blast wave itself. Insights into the break-up process during structural failure and the resultant debris throw characteristics expressed in terms of fragment mass distributions, initial velocities and launch angles, are thus essential to assess the significant potential explosion hazard. However, to date the data basis for hazard assessment and model development on debris throw of masonry structures is limited. In this article, we present the results from shock-tube experiments of single-span masonry walls subjected to dynamic blast loads characteristic for far-field explosions and free-field blast propagation. Reflected peak overpressures in the tests ranged from 100 to 150 kPa with corresponding maximum impulses of approximately 2000 kPa ms to 3000 kPa ms. A new methodology based on high-speed stereo video imaging allows to analyze the break up process and the resulting debris sizes, launch velocities and three-dimensional launch angles before the debris hit the ground. The data derived can be used for empirical predictions of debris launch characteristics as well as for the validation of numerical simulations aimed at the proper assessment of hazardous secondary blast effects from masonry failure