Explosions Blast pressure

Vapor cloud Explosion blast pressures Indoor gas build... 

Sad6e et al. (1976-1977) give a detailed description of structural damage due to the explosion and derived blast pressures from the damage outside the cloud... 

The fuel-air explosion produced, in a large area covered by the cloud, substantially higher blast pressures than would be expected from a 100,000-kg TNT surface blast. 

This section first presents literature review on pressure vessel bursts and BLEVEs. Evaluation of energy from BLEVE explosions and pressure vessel bursts is emphasized because this value is the most important parameter in determining blast strength. Next, practical methods for estimating blast strength and duration are presented, followed by a discussion of the accuracy of each method. Example calculations are given in Chapter 9. 

TNT Equivalence. Explosion strength is often expressed as equivalent mass of TNT in order to permit estimates of possible explosion damage. For BLEVEs and pressure vessel bursts, using this equivalence is unnecessary because the methods mentioned above give explosion blast parameters which relate directly to the amount of possible damage potential. However, the concept of TNT equivalence is still useful because it appeals to those who seldom deal with blast parameters. For reasons explained in Section 4.3.1, BLEVEs or pressure vessel bursts catuiot readily be compared to explosions of TNT (or other high explosives). Only the main points are repeated here. 

Explosion calculations, 499-504 Estimating destruction, 501 Overpressure, 502 Pressure piling, 501, 504 Relief sizing, 505 Scaled distance, 502, 503 Schock from velocity, 503 TNT equivalent, 499-504 Explosion characteristics of dusts, 515 Explosion suppression, 518 Explosion venting, gases/vapors, 504 Bleves, 504 Explosions, 482 Blast pressure. 496 Combustion, 482 Confined, 482 Damage, 498-501 Deflagration, 482 Detonation, 483... 

All flow behind the wave is stopped, and pressures are considerably greater than side-on. The pressure in normally reflected waves is usually designated pr(t), and the peak reflected overpressure, Pr. The integral of overpressure over the positive phase, defined in Equation (13), is the reflected specific impulse ir. Durations of the positive phase of normally reflected waves are almost the same as for side-on waves, thigh explosive blast sources than have most blast parameters. 

Reinforced concrete is the most commonly used construction material for structures designed to resist explosive blast loads. It is used extensively in blast hardened structures because of its strength, ductility (when properly designed), mass, penetration resistance, relative economy, and universal availability. Its strength, mass, and ductility provide high resistance to the extreme blast pressure (psi) and impulse (psi-ms) loads. It is important to remember that (unlike in static load design) in the... 

Breeching is a local perforation of the concrete element by the extremely high blast pressures of a close explosion. High velocity concrete fragments can result. Breeching failures are controlled by providing adequate reinforcement, concrete thickness and standoff distance to the explosive. 

Overpressure - Is any pressure relative to ambient pressure caused by an explosive blast, both positive and negative. 

The propagating blast wave at any instant in time extends over a limited radial distance as the shock/prcssure front travels outward from the explosion. The pressure is largest at the front and trails off to ambient over a distance, L, the blast wave length. Values of L for high energy explosives can be obtained from I M 5-1300. In the low pressure range, the length of the blast wave can be approximated bv ... 

One might note the striking similarity between Cases I and II. In both, a crucible failure allowed water to enter and mix with molten titanium. Steam (and hydrogen) formed and the pressure increased so as to bulge the crucible and rupture the safety discs. Tamping the water-metal mix by the fall of the electrode then caused a major explosion. No injuries resulted in the Case II incident because the vault walls provided protection. No data were available to allow an estimation of blast pressures, but as described, the vault construction maintained its integrity and the wave was forced to exit from the bottom. 

No No Primary high explosive, Extremely pressure/impact sensitive. Used in ammunition primer and blasting caps ... 

R. Schall, Methoden und Ergebnisse der Detonationsdtuckbestimmung bei festen Sprengstoffen (Methods and results of the determination of blast pressure of solid explosives), pp 629—35... 

Air-Blost Effect Air Blast Energy Air Blast Impulse and Air Blast Pressure. See under Blast Effects of Air, Earth and Water Air-Blast Meter. See under Blast Effects, etc Air-Blast Pressure from Small Charges of Various Explosives are discussed in OSRD Rept 3479(1944)... 

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