Risk analysis of an urban environment under explosive attacks in Tehran

In recent years high explosive bomb attacks have been increasingly directed against civil structures by various terrorist organizations. This paper describes a numerical method for assessing the interaction of high explosive air blast within the complex geometrical type of a congested urban environment. The first step in predicting blast effects on a target is to predict blast loads on it. In this study a computational fluid dynamics program and analytical methods developed by the Federal Emergency Management Agency (FEMA) were used to solve two and three dimensional air blast problems. Explosions in confined spaces (mines, buildings, large vehicles) which cause structural collapse are associated with greater morbidity and mortality. The reflected pressures for explosive detonations are two to thirteen times greater than peak incident pressures. A rough estimate of the total casualties following such events are the result of the composition and amount of involved materials, surrounding environment, delivery method, distance between the victim and the blast, crowd density and any intervening protective barriers or environmental hazards. The extent and severity of damage and injuries in an explosive event cannot be predicted with perfect certainty. Despite these uncertainties, it is possible to give some general indications of the overall level of damage and injuries to be expected in an explosive event based on the size of the explosion, distance from the event and assumptions about the construction of the building.