Internal explosions cause a shock wave and an overall quasistatic, or fill pressure in the explosion room. The shock wave and fill pressure will propagate outside the explosion room through any openings or failing walls. There has been much study and numerous fast-running methods developed to predict the shock pressure histories and quasistatic pressures in the explosion room. These methods have evolved from simple, single room codes developed for explosive safety design work into larger, multi-room codes, such as the BlastX  and VAPO  codes, which calculate blast loads for a fixed multi-room geometry. There has been very limited development of fast-running codes that integrate blast load propagation and structural response to calculate blast propagation outside the explosion room through failing walls and doors. Recently, the Defense Threat Reduction Agency (DTRA) and the Air Force Research Laboratory (AFRL) in the U.S. and the German government have sponsored test programs to investigate internal blast propagation through failing walls. Also, DTRA has sponsored development of FRIDAM (Fast-Running Internal Damage Assessment Methodology) to predict blast pressures, building damage, and occupant injuries in buildings from internal explosions. FRIDAM is a semi-empirical approach with coupled blast load and structural response calculations that has been developed using the test data from thirty-one internal detonation tests sponsored by DTRA and AFRL with charge weights up to 25 lb. (11.4 kg) TNT in multi-room test structures with internal walls that have typical building construction.
Read the full PEC Publication by Dr. Charles Oswald, P.E.