Five Dominant Fatality Mechanisms in One Scenario

One of the major advantages of doing quantitative risk analyses (QRA) is that it takes into account all of the the five major hazard mechanisms in an explosives event.  Those mechanisms are full body displacement from overpressure, lacerations from broken glass, injury from building collapse, and being struck by vertical or horizontal debris.

Usually two or three mechanisms share dominance in a particular scenario as one moves downrange from ground zero.  But recently we came across a few scenarios where all five mechanisms have dominance at some point.

We were doing work for the Institute of Makers of Explosives, pouring over thousands of charts generated by the engine in the IMESAFR V2.0 QRA software.  We were studying charts that showed the probability of fatality given an event for a single individual for each mechanism vs the distance downrange.  Shown below is a scenario where all five mechanisms exert dominance at one point or another.

2.2.1-#217-0.0-deg---Pre-engineered-metal-building-(PEMB)-vs-Large-unreinf-masonry----Annealed---25

In this scenario, the potential explosion site (PES) is a pre-engineered metal building and the exposed site (ES) is a large reinforced masonry structure.  The ES has 25% annealed glass and is at 0 degrees azimuth (normal to the door side).  There is no barricade and the 100K lbs of explosive has no primary fragments.

The red line is the overall probability of fatality given an event [P(f|e)] and the various colors represent the P(f|e) of the five primary hazard mechanisms.

Out to about 500 feet, the greatest hazard is from overpressure.  From about 500-600 feet, horizontal debris and building collapse share the spotlight.  Then from about 600-1,250 feet, building collapse dominates.  From about 1,250-1,800 feet, vertical debris is most likely to cause a fatality.  Beyond that, as in almost all scenarios, glass takes over as the primary risk.

For more information on the Institute of Makers of Explosives or IMESAFR, please go to www.ime.org.

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