# Additional weight on Truss



## reprosser (May 5, 2010)

I have a shop and tractor shed that are pole buildings with Truss roof.

I want to know how much weight I can safely hang from the bottom (joist?) of the truss. I don't want to pull an engine block, but may have needs to hang things from time to time.

I have the spec for my Truss, but I don't know how to read it.

BCDL (botom chord dead load) is listed at 5.0 psf. I hope that does not mean I can only hang 5 lbs, because I think the lights weigh that much.

There is other data on the spec, so let me know if I can provide more info.


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## Wuzzat? (May 5, 2010)

reprosser said:


> I have a shop and tractor shed that are pole buildings with Truss roof.
> 
> I want to know how much weight I can safely hang from the bottom (joist?) of the truss. I don't want to pull an engine block, but may have needs to hang things from time to time.
> 
> ...



5 PSF is a distributed load, you want to load it with a concentrated load.

You need to post the Area Moment of Inertia, I, in inches&#8308;, and 
the modulus, E, in PSI.  

Also, how far apart are the trusses and what distance do they span?


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## reprosser (May 5, 2010)

Ill just posts the data sheet.


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## Wuzzat? (May 6, 2010)

From note 4, the bottom chord supports a 10 psf live load.

If no math mistakes and no incorrect assumptions, 
for a 30' span and assuming 2' spacing, 2x30 = 60 sf.
10 psf with 60 sf = 600# distributed over 30'.

It's 20# per foot of span, so you could hang 30 ea. 20# weights.

For a single concentrated load in midspan, I'd ask the manuf.  And ask him about the 30 ea. 20# weights; solving a textbook problem is one thing but this is the real world.

If it were a single piece of wood I could probably figure it.


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## reprosser (May 7, 2010)

These trusses are used in my tractor shed. 5 trusses spaced 12 feet apart.


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## Wuzzat? (May 7, 2010)

reprosser said:


> These trusses are used in my tractor shed. 5 trusses spaced 12 feet apart.


And the span doesn't look like 30', either. I'd ask the manuf. 
or put up your own joist designed to carry whatever max. concentrated load you want for it.  The calc. for this second option should be easy.


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