Development of an Improved Methodology for Predicting Airblast Pressure Relief on a Directly Loaded Wall

The interaction of an airblast wave with a structure, and the blast wave propagation around and over the structure is of significant importance. In order to protect a structure from the airblast produced by such explosive threats as terrorist bombs, a facility designer must possess an adequate knowledge of the expected blast wave loading. Of greatest importance are pressures and impulses on the directly loaded face of the structure, since it is typically subjected to the highest (reflected) pressures. It has long been recognized that reflected pressure time histories can be strongly influenced by pressure relief from the free edges of the loaded wall. The relief wave can significantly reduce the magnitude of the late-time portion of the positive reflected pressure phase, resulting in a substantial decrease in the peak impulse load. Most current predictive methodologies attempt to account for the relief wave and its effect on impulse. Unfortunately, these methods tend to be rather inaccurate because the exact manner in which the relief wave is manifested is not accurately defined. The US Army Engineer Research and Development Center has developed an improved methodology to predict the effect of pressure relief. This paper presents the basis for the methodology and its practical application.