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Re: "Blown Away"

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they are also not at the front entrance of a building where a lot of
people will be.

Stan Scholl, P.E.

On Tue, 06 Mar 2001 08:02:31 -0500 Walter Sawruk <sawruk(--nospam--at)>
> Looking at this from a slightly different perspective, there are 
> situations 
> where portions of structures are purposely designed to be 'blown 
> away' such 
> as in damage limiting construction per NFPA 68 "Guide for Venting 
> Deflagrations".  This practice is common in process plants where 
> wall 
> and/or roof panels are designed to blow out to relieve internal 
> pressure 
> due to accidental explosions or deflagrations thereby preventing 
> failure of 
> the superstructure.  However, the important point here is that the 
> panels 
> are designed to remain intact and tethered to the main structural 
> system.
> Walter Sawruk
> EQE International, Inc.
> Shillington, PA
> Email: ws(--nospam--at)
> At 09:06 AM 05-03-01 -0600, you wrote:
> >Recently, an architect client of mine and I were discussing a 
> feature of a
> >commercial building we were working on. He does lots of convenience 
> store/fast
> >food combination facilities. One client has a "doghouse" at the 
> front entrance
> >of the store, a "penthouse" type structure that allows a sign-logo 
> above the
> >entrance that extends about eight feet or so above the parapet 
> line.
> >
> >The doghouse itself is CFS supporting metal cladding, which sits on 
> the beams
> >and joists of the main structure.
> >
> >The design drawings given me showed a CFS structure that was WAY 
> >under-designed
> >to resist code-specified wind forces, and I proceeded to design it 
> correctly,
> >which made for a much "beefier" structure, particularly where the 
> roof members
> >and overall connnections were concerned. When he saw this, he had a 
> negative
> >reaction. "Too much", he said.
> >
> >I pointed out to him that we were building in an area where the 
> design wind
> >speed is 120 mph (three-second gust). His response was "oh, that 
> doesn't 
> >matter,
> >if they had a hurricane, the doghouse would just be blown off, and 
> they could
> >build it back again".
> >
> >I had NEVER heard of this approach before! In essence, he's saying 
> "just 
> >design
> >it to handle gravity loads and don't worry about wind, this is not 
> an occupied
> >portion of the structure. If it gets scoured off, no big deal".
> >
> >Have any of you designed "components and cladding" type portions of 
> a 
> >structure
> >under this approach? The architect insists it is perfectly valid: 
> "we do 
> >it all
> >the time". Of course, this guy is the "Wal-Mart" of architects in 
> our market,
> >and is used by developers here because he works cheaply, and 
> doesn't get in
> >their way.
> >
> >I'm starting to rethink my relationship with him on this basis, but 
> I'd 
> >like to
> >know if this is perhaps more commonplace than I realize, and if I'm
> >"overreacting". I just can't imagine a building department anywhere 
> allowing a
> >portion of a structure the possibility of being "blown away".
> >
> >Thanks.