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Q: Need to know correct steel beam size ( Answered,   0 Comments )
Subject: Need to know correct steel beam size
Category: Science > Physics
Asked by: ckrause8834-ga
List Price: $10.00
Posted: 17 Oct 2006 15:34 PDT
Expires: 16 Nov 2006 14:34 PST
Question ID: 774484
I need to fasten a beam to the exterior wall of a pole barn for
lifting/hoisting an item out of a vehicle. The weight of the item is
1000Lbs or less and will be lifted by cable winch/hoist from the
center of the beam. The beam will be mounted above an existing 14' x
14' garage door with wood posts on each side. The span the beam will
make is 174" on center to where it will be bolted through the posts.
Two 1/2" grade 8 bolts will be used on each end. I was thinking a
6x2x1/4 steel tube would suffice, but being cost sensitive would like
to use the smallest/lightest beam required (channel is an option).
Also, the winch/hoist will be mounted to the outside face, not
structure side, of the beam as opposed to hanging from the center (for
clearance purposes). This means the lifting point would be 3" (2" beam
and 1" spacer for ribbed siding) from the supporting post's face and
1" from the center of the beam.

So, what is the lightest beam that could be used and would the
mounting position of the hoist affect the strength of the beam or
fastening method to the support posts in such a way as to make
prohibit construction ?

If it matters: Deflection or bending in the center 12" of the beam
should be minimal because the hoist is bolted to the beam and we don't
want the fasteners (3/8") to shear. The mounting holes can be slightly
oversized to accept some movement, maybe up to 1/8".
Subject: Re: Need to know correct steel beam size
Answered By: redhoss-ga on 17 Oct 2006 16:18 PDT
Hello ckrause8834, I just ran your beam on a program I have and the
deflection at the center is 0.275 inches. Does that sound okay to you.
Please ask for a clarification if you want to try something else.


Clarification of Answer by redhoss-ga on 18 Oct 2006 07:32 PDT
I was in a hurry yesterday evening when I answered your question and
forgot to give you some other info. Normally deflection in a
structural beam is limited to L/360. In your case that would be
174/360 = 0.48 inch. So, your 6x2x1/4 tube is a good choice. Your
bolting arrangement to the posts sounds fine to me and I wouldn't
oversize the hoist mounting holes. The tube material would deform
before the bolt would shear anyway. The torsional load in the tube due
to the mount being off center is not significant and I doubt that you
will even notice the twist. Again, please ask for a clarification if
you have other concerns.
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