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[SEAOC] Re: [SEAOC] RE: TILT-UP BUILDING WITH GYPSUM ROOF DIAPHRAGM

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On Fri, 13 Dec 1996 Amaloyan(--nospam--at)aol.com wrote:

> Fellow Engineers;
> 
> A friend of mine (who is not on the net) was asked to inspect a tilt-up
> building.
> To his surprise (and mine) he found the roof diaphragm to be composed of 12"
> to 14" of GYPSUM looking material. The roof framing members are steel beams
> at 8' o/c.
> This gypusm looking products are in 8' panels and are resting or dropped
> between these beams. The walls are concrete. Now the big question is how does
> this work as a horizontal diaphragm? There is no wood or steel in the panels.
> 
> If any of you have encountered a situation like this, it would be appreciated
> to hear your comments. 
> 
> How does one seismicley retrofit a building with these characteristics?
> How does one anchor the walls and how does the shear at the boundaries (if
> any) transfer to the shear resisting elements?
> 
> I was thinking of suggesting a horizontal rod bracing system to substitute
> for the 
> lack of a good horizontal diaphragm. Any comments?
> 
> Ara Maloyan P.E.
> Amaloyan(--nospam--at)aol.com
I've seen pured gypsum roofs. They provide NO diaphragm action at all. 
Your suggestion, to use horizontal rod (or other cross) bracing, is 
probably the best solution.
Bob

.    .    .   .   .  .  .  .  . . . . . ...........................
Bob Shilling, SE             Berkeley, CA          shilling(--nospam--at)emf.net
KK6QQ         				                   MSA S-10
'91 R100 Classic, "Tornado"    ABC#2063                   DoD# 1195
"Give me my cycle, and a star filled sky above..."
                         'The Wild One' Johnny Horton(1925-1960)
      "This alligator walks into a bar and ..."   Horizon Kent

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