Design for Internal Quasi-Static Pressures from Partially Confined Explosions

In the early 1980s, results from a series of tests in a partially confined enclosure were used to develop a prediction model for internal gas pressure. The test variables were Charge Weight, W vent area, A, and frangible panel weight, w. The gas pressure time history was measured in each test. A semi-empirical prediction model for predicting scaled gas pressure impulse, igW13 was developed using the Peak Gas Pressure, Pg , and a decay rate based on the instantaneous gas pressure, Pgt, and vent area Avt, and the constant scaled parameters maximum vent area AVV23, WV ratio, frangible panel weight wW13, and shock impulse on the frangible panel, irW13. A computer program was written to predict the total quasi-static gas pressure impulse. The program is now named FRANG and is referenced by the tri-service design manual Structures to Resist the Effects of Accidental Explosions Navy NAVFAC P-397, Army TM5-1300, and Air Force AFM 88-22. The work was presented in at the 21st DDESB Seminar Effect of Frangible Panels on Internal Gas Pressures by J.E.Tancreto and E.S. Helseth. FRANG is widely used to calculate the internal gas pressure loads on confinement structures.