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Re: Diaphragms -Reply

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>>> <Amaloyan(--nospam--at)aol.com> 08/21/97 12:39am >>>
In a message dated 97-08-19 11:13:17 EDT, you write:

<< 1. Do any of you use formula 31-1, section 1631.2.9 for calculating
 >diaphragm load in single story buildings?
 >
 >2. When figuring diaphragm load do any of you use the weight of
 >diaphragm + weight of walls tributary to diaphragm which are
 >perpendicular to seismic load?
 >
 >3. When figuring diaphragm load do any of you use all four walls
 >tributary to diaphragm?
 >
 >Consider this as my survey of the week :)
 >
 >Mark D. Baker
 >Baker Engineering >>

Dear Mark:

See UBC 1604.4
This code section requires 20 psf dead load in addition to the diaph.
loads
to be
added in seismic and vertical design. I would use the same D.L. in
residential
and commercial construction. If you want to be very accurate you can
calculate
the D.L. of each wall in each direction and dump 50% to the roof diaph.
and
50% to the floor diaph. (if multy story). 
Also see  UBC 1628.1 #2
"Where partition load is used in the floor design, a load of not less than
10
psf
shall be included."
This 10 psf is used per floor and per diaph. That means 10 psf to the
roof
and 20
psf for the second or other floors. (10 psf to floor below + 10 psf from
walls below).

All interior partitions and  walls are some how connected to the floor and
roof diaph.

Happy calculating,

Ara Maloyan  P.E.



Ara, I'm puzzled to hear that you would include a 10 psf contribution to
levels above and below.  Never heard of doing it that way and always
thought it was just 10 psf per floor level (excluding the roof) added to W.
Though obviously walls are braced to structure above except at
perpendicular partitions, that seems overly conservative to me.   I'm
curious how others have interpreted it?  This is a pretty common
question for design of an office bldg.    Thanks.