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Re: Blast Resistant Design

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While I can't answer your first question, but can offer some thoughts on
number two.

The concept behind blast design is typically to channel the blast in a
direction that would minimize harm to the public.  Obviously, you don't
want the blast to "explode" into the building.  This typically leaves
"directing" the blast away from the building.  If the room to be design
for blast is only a single story piece of the structure (most typical
case), then either a section of roof or exterior wall can be designed to
be the "weak" link to direct the blast.  If there is structure overhead,
then it will have to be an exterior.

Basically, the idea is to design a code determine size of either roof or
wall to be a weak link.  The intent is that this piece of wall will be
extremely weaker than the other walls and/or roof sections.  Therefore,
when the blast load "hits" the exterior skin (roof or walls), the
pre-determined/designed section will provide explosion relief.  The
sections to be designed as the weak are picked by which direction will not
endanger the public.

Hope this helps.


On Fri, 6 Oct 2000 jwhitty(--nospam--at) wrote:

> I have an H-2 structure that contains an explosive process...
> BOCA (governing building code) refers me to the NFPA 68 dealing with blast
> questions are these:
> 1.  Does the H-2 classification require explosion resistant design?
> 2.  If so, the NFPA seems to indicate that you can vent or design the
> structure to resist the peak blast loading.  What's wrong with allowing the
> lightweight siding to "blow off" the building?  Is it because of danger to
> anyone who may be in the area or surrounding structures at the time?
> Obviously, if I can design the building with a steel skeleton and
> lightweight roofing/siding it will be considerably less expensive than a
> concrete/reinforced cmu structure designed to resist blast.
> I'm looking for guidance here.  Any help would be greatly appreciated.
> Thanks
> John Whitty, P.E.