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Re: TRUSS QUESTION

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I'd use 20 psf live load, if you're not in a snow area.

__________________
John P. Riley, PE, SE
Riley Engineering
20 Oakwood Drive, Blue Grass, Iowa 52726
Tel & Fax:  319-381-3949
jpriley485(--nospam--at)peoplepc.com


> Juan:
> 
> For static gravity loads on a steel truss, I would normally select the
> truss configuration that puts the diagonals in tension. This would be a
> Pratt Truss. If you have moving loads (such as a bridge) or reverse
> loads (such as wind uplift) the diagonals will sometimes be in tension
> and sometimes be in compression. Under those conditions, a Warren Truss
> is more common. A Scissors Truss is normally used when the ceiling and
> roof need to be pitched. It creates an outward thrust on the walls. For
> a  high  pitched roof, a Fink Truss might be more appropriate.
> 
> I would think that you would want to design for some live load to
> account for a hard rain accummlating on the roof before it has time to
> drain, workmen on the roof or the occasional hailstorm. I believe in
> different parts of the US, they require a minimum live load of 12 psf or
> 20 psf depending on how much tibutory area the member is supporting.
> 
> I hope this helps!
> 
> 
> Jim Kestner
> 
> 
> 
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