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Re: Blast Pressure

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Shawn Freilinger wrote:

<< I am working on an observation tower in Florida for the
 USAF.  The wind speed is 130 MPH per ASCE 7-95 and EIA/TIA-222-F.  The
 kicker is that they have given me a 3.7 psi blast pressure that will last 47
 msec.  The translates to 533 psf!!  I will be contacting the AF tomorrow to
try and get
 information, but I was wondering if anyone on the list has either applied a
 blast pressure to a structure or maybe has some literature about how to do
 it. >>

Shawn.  

A blast pressure of 3.7 psi is not as bad as it seems.  The key is the
duration of loading of only 47 ms.  The different military agencies have
design guides of all sizes and shapes, but the first reference that I would
suggest, as was noted by another responder, is Army Technical Manual TM
5-1300, Design of Structures for the Effects of Accidental Explosions (or
something like that).  Also, I would suspect that when you contact the AF,
they'll be quit helpful.

Blast design is in some ways similar to seismic design.  First is to take into
account that the response period of the structure is much longer than the
duration of the blast wave.  There are formulas in the various design manuals
for reducing the pressure based on a calculation of the structural response
period of the tower.  Second, you can take into account the ductility of the
structure.  I recall using a ductility factor as high as 10 in one case.

I'm not at work right now, so this is off the top of my head.

Carl Sramek