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Re: Diaphragms

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Mark Baker wrote:

> 1. Do any of you use formula 31-1, section
> 1631.2.9 for calculating
> diaphragm load in single story buildings?
>

No.  Always seemed to me that the intention was to
counterbalance diaphragm load understatement
created through the use of 28-8

> 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?
>

Yes.  I generally tend to estimate other aspects
of my lateral loads conservatively, (Roof DL, wind
exposure) and so will often ignore parallel walls
and interior partitions unless there are unusual
conditions.  If I've got multistory I usually
include parallel walls as well as interior
partitions (typically I figure 10psf unless I see
it's clearly more) throughout my lateral analysis
of the major systems (which can be conservative
with respect to the diaphragms).

> 3. When figuring diaphragm load do any of you
> use all four walls
> tributary to diaphragm?

See my response above.



Stan Johnson
BS, EIT, What about weight of nails.  Once
encountered a situation where weight of bolts in
the roof trusses amounted to more than 5% of total
roof weight!  :)   The metal side plates were even
more! :))