Blast Resistant Building Explosion Forces

Explosion or Blast Forces
An explosion or blast is best defined as a sudden release of energy.  Catastrophic effects occur when such an event is created by a large amount of solid or liquid materials, airborne combustible dusts or ignitable gases or vapors.  In such an event, the initial force of the explosion or blast creates a wave of compressed air that emanates from the source in all directions.  What should now be defined as the face or front of any object that the force encounters is first subjected to what is most commonly referred to as either "side-on" "on-side" or "incident-side" overpressure.

While the term may vary, the serious nature of this destructive force does not.  And since this is a force that creates air pressure, it is most commonly measured in pounds per square inch, or "PSI".  The explosion or blast wave then propagates or expands at a certain velocity and to a certain distance according to the amount of material, dust or gas that explodes.  Accordingly, the closer an object is to the source, the higher the pressure it will encounter. 

As you may have already guessed, there is then a second event where the pressure from the explosion or blast force recedes or returns to the point of origin.  This is most commonly referred to as "reflective" pressure, which strikes any originally encountered object from the opposite or rear side, assuming it remains standing.  Finally, the amounts of time during the initial and secondary events are defined as "positive duration" and "negative duration", and are generally measured in milliseconds or "ms".

Therefore, at a minimum, Bebco requires the On-Side Pressure, Blast Duration and Reflective Pressure to accurately bid a project, which will be used to determine structural integrity based on the overall dimensions of the shelter you require for your application.  For a highly detailed and unbiased explanation of explosion or blast forces and how they can be accurately calculated, complete with diagrams, we recommend the review of the pdf documents available at these links: Blast Loading and Blast Effects on Structures & Design of Modular Blast-Resistant Steel-Framed Buildings in Petrochemical Facilities