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I’m installing a W16x26 steel beam, 20’ clear span underneath floor I-joists, 12” deep and 16”OC. The beam is plenty stout in terms of sheer and deflection but needs lateral bracing to account for bending.

Usually folks have joists butting into these beams so they don’t need to worry about it.

My question is, how is this generally done? Based on my calcs, I need to make the bracing 48” OC along the beam.

How is this generally done in a situation like this? My plan was to bolt or weld brackets into the bottom 1/3 of the beam every 48”, and have a 2x4 or steel going at 45 degrees up and securing to the floor joists above, maybe 2 or 3’ from the beam.

Would this be acceptable? Respectfully, I Don’t need advice to hire an engineer, the beam is almost in place, just looking for your thoughts on the bracing.

Thanks!

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  • Perhaps I'm being thick... but what bending? Lateral bending should be resisted by the flanges. Quite strongly.
    – Olivier
    Commented Nov 4, 2020 at 0:47
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    Are the floor joists attached to the steel beam or are they just resting on it? It seems to me that it would be easy to attach steel clips to the undersides Or sides of the joists on both sides of the beam which would hold the joists to the beam and would make the joists into lateral support for the beam.
    – Jim Stewart
    Commented Nov 4, 2020 at 1:15

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Are you sure your steel beam is a W16X26?

I doubt that beam needs lateral bracing, because that size beam will support about 31,000 lbs. per foot for a 20’ span. (That size beam can support my entire house and 3 of my neighbor’s houses.)

Lateral bracing is required when a beam is fully stressed (or overly stressed) and you need to keep the beam from buckling and “laying over”. This beam is not overstressed.

If you start drilling holes in the flanges, you’ll weaken the beam...don’t. If you need to attach something, drill holes in the vertical web.

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  • Thanks for the comments so far folks. It is definitely a w16x26. Our snow load is 120 plf which is what tips the scales. The design is definitely stout. Maybe I’ll just forego the lateral bracing for now and see how things go...I did end up drilling little 3/8 holes in the top flange do I can secure the beam to the top plate that the joists rest on, just to shore things up.
    – Patrick Erley
    Commented Nov 4, 2020 at 2:11
  • So a 2x6" plate is bolted to the steel beam and the floor joists are toenailed to the plate?
    – Jim Stewart
    Commented Nov 4, 2020 at 5:03
  • Yes that’s correct. It’s a double top plate and the beam will be bolted to that, and the joists are toenailed to the plate.
    – Patrick Erley
    Commented Nov 4, 2020 at 20:08

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