Pole Barn Beam

[JStructsteel]

What are your guys thoughts on a pole barn garage door beam? Its a 18' span, the builder wants to split the beam and have it on each face of the column, bolted thru. Do you feel the load will be shared? Its a 48' span across. Trusses at 4'-0" o.c. I was going to make them bolt/nail the beams together and use a hanger of the side of the column.

 

[JAE]

If there is lateral wind on the beam, which there is, then the two separate beams are much weaker than the one single beam when bending perpendicular to the wall/door.

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[JStructsteel]

Actually there is minimal lateral load due to the door being on tracks on the side.

Any thoughts on having it front and back face, splitting the load? I think a span that large I would want some blocking in between too.

 

[dik]

Are they timbers? Can you use a Simpson cap type connection?

Dik

 

[JAE]

With thinner beam width you have diminished flexural capacity per the NDS so blocking between would be good to get the two beams working together to some degree.

If there is wall above the door, then there is some wind force on the beam. I agree that the tracks bring the wind load primarily into your king studs or posts on each side.

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[JStructsteel]

the beam will be 2 beam built up parallam, the posts 6x6. I was originally thinking a hanger, but the builder asked about front and back face

 

[jayrod12]

I'd be ok with front and back face provided they block between the beams at a reasonable spacing, say 16" o/c and then provided a couple of thru-bolts at each blocking location to foce the two plies to move together.

 

[BAretired]

16" o/c? Wow!

BA

 

[KootK]

Will the trusses sit on top of both plies? That would nice. It might also be slick to use 6x6 post stubs as your blocking and position one beneath each of your trusses if that is possible. Design the bolting to transfer the individual truss loads etc.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

16" o/c? Wow!

Too much? or not enough?

 

[dhengr]

Jrisebo:
You see the contractor’s idea for that beam detail fairly commonly in pole barn construction. The fact that it works has much more to do with luck, the bldg. never seeing the full design loads, and our general factors of safety; than it does to good engineering design or detailing. Larger beams with a good bearing seat cut on the top of the column are much stronger and less inclined to settlement, than if their end connections are through nailed, bolted or on hangers at the column reaction. The two separate beams must be blocked and/or tied together (interconnected) if you want them the act as a single unit, to the extent that the various loads must be transferred btwn. them. Only the exterior beam will pick up outside lateral loads, without help from the interior member without proper interconnection. Only the interior beam will pick up roof truss loads to the extent that the trusses rotate at their bearings, or to the extent that the inner beam crushes and deflects to finally bring the outer beam into play. And, the inner beam was probably not designed for 75-80% of the roof load reaction.

 

[BAretired]

Quote (BA)
16" o/c? Wow!

Too much? or not enough?

Well, if you are going to place blocks at 16" o/c, it would probably be easier to use a continuous separator with bolts at 16" o/c.

I prefer KootK's idea of placing blocks at truss locations. Trusses are usually spaced at 2' or 4' centres for a farm building, so that would seem to be a reasonable spacing for blocking.

BA

 

[jayrod12]

My experience with pole barns is trusses at 4 ft. I didn't like that spacing for blocking. Toyed with putting 2 ft, but figured more is better.