Probabilistic Risk Assessment for Improvised Explosive Device Attacks That Cause Significant Building Damage

Abstract

Most vulnerability assessments assume that an improvised explosive device (IED) will reach maximum TNT equivalency, and that the IED will successfully detonate. These assumptions will tend to overestimate actual blast-load effects. The paper develops an IED probabilistic risk-assessment model using a systems model for IED attacks based on the reliability of IEDs and by characterizing the human aspects of an IED attack’s operational effectiveness from existing databases of terrorist incidents. The analysis includes estimates of the probability of threat, hazard, and loss for large commercial buildings in the United States. It was found that annual fatality risk for building occupants is similar to acceptable risk criteria. This suggests that strengthening buildings against progressive collapse may not be warranted unless there is a specific threat against a building.