A Computational Approach to Assessing Blast Damage in Urban Centers Using AUTODYN

Recent terrorist attacks have prompted considerable interest in predicting damage to structures that could result from explosive blasts in densely populated urban environments. This is a particular concern for government and military organizations wishing to improve the safety of facilities and insurance providers who want to quantify risks. Blast waves from explosions are characterized by a shock front propagating into the surrounding air, followed by an exponential decay in pressure. Structural damage can be caused by either the magnitude of the peak pressure or the impulsive loading over time. Thus, any assessment of damage requires accurate computation of the entire pressure history on the structure. Semi-empirical approaches, such as CONWEP, although able to predict free-field and single-reflected pressures accurately, are unable to account for the effect that the urban environment has on amplifying, dissipating or focusing the blast wave. This paper describes a numerical finite difference approach, using the non-linear dynamics program AUTODYN, which allows an accurate prediction of the pressure fields that develop as a blast wave propagates through an urban environment by recursively remapping the solution through numerical regions that expand to track the evolving shock front. Data for specific urban layouts can be imported into AUTODYN from geographic information system (GIS) services.