Characteristics of Free Air Blast Loading Due to Simultaneously Detonated Multiple Charges

Extensive research has been conducted to investigate the characteristics of blast load due to single charge explosion, including numerical simulations and experimental blast tests in both unconfined and confined environments. Further, available guidelines for blast resistant design such as UFC-3-340-02 (2008) and ASCE 59-11 (2011) provide details to predict blast loads on a structure subjected to single charge explosion. However, blast load characteristics due to multiple charge explosions are poorly discussed in available literature. In this paper, commercially available Hydrocode, AUTODYN is calibrated for single charge explosions. Based on a comparison between numerical simulation and UFC prediction, correction factors for peak reflected pressure and positive reflected impulse as a function of charge weight, scaled distance and mesh size of the numerical model are proposed to minimize the errors in simulations. The calibrated AUTODYN model is then used to conduct parametric studies to investigate the effects of charge weight, scaled distance, number of charges and distance between the charges on the characteristics of free air blast load due to simultaneous detonated multiple charges. Numerical simulation results are used to derive analytical formulas for predictions of peak reflected pressure ratio and positive reflected impulse ratio between single and multiple explosions. The discussion is made on characteristics of free air blast load due to simultaneous detonated multiple charges.