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RE: Weights for design

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When I first started out, I used to calculate the roof
dead load (usually 15 -16 psf in this area for an
industrial roof) and use that as my design load, but
I quickly learned that some areas had larger loadings
due to sprinklers, heavier duct work, industrial lines
etc, and so I bumped my loadings to 20 psf.  Then I
found out architects often changed the style of roof
without always informing me---once the roof totaled
23 psf but fortunately the joists were OK.  Then we
had a roof collapse in an accident.  The roof dead load
(no sprinklers, etc) totaled 30 psf due to build up of
roofing over the years.  I now design for 25 psf and
nobody ever questions it much.

On 8 Mar 2005 at 12:49, David Maynard wrote:

> Per ASCE 7:
> Fiberous Glass Insulation is 1.1 psf per inch of thickness.
> For sprinklers, I break down what is being used for pipe, how often it
> is being used, the volume of the pipe and the additional weight due to
> the water.  Tack on a little bit of fudge factor for fittings, spread
> this load out over the entire roof area, if I see it is possible,
> badda-bing badda-boom, I have a dead load.
> For industrial buildings been known to have upwards of 10 to 12 psf
> for dead load, but that includes roof sheeting, purlins, and what have
> you.  I do, however, take a quantitative look at things, and come up
> with a good, and even conservative, additional dead load onto the
> structure.
> Dave Maynard, PE
> Gillette, Wyoming
>   -----Original Message-----
>   From: David Smith [mailto:smith1129(--nospam--at)]
>   Sent: Tuesday, March 08, 2005 12:22 PM
>   To: seaint(--nospam--at)
>   Cc: smithassociates(--nospam--at)
>   Subject: Weights for design
>   I am reviewing the loads for wooden trusses on a church roof.  The
> architect specified R30 insulation and automatic sprinklers.
>   It looks like the weights for each of these can vary all over the
>   map.  I
> would appreciate seeing some typical design weights used by the rest
> of you.
>   Dave Smith
> --
> No virus found in this outgoing message.
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