Wood planks over steel beams - bracing?

[Azmarya]

I have a sidewalk shed made up of header beams and cross beams. 2x10 wood planks will be placed over the cross beams (not anchored) for workers to walk on top and do their thing. Can I consider the compression side laterally fully braced for these cross beams because of the wood planks?

Thanks

 

[KootK]

I would normally say no. With the unanchored planks, you don't really have a diaphragm and nothing restrains your cross beams laterally. Therefore the cross beams probably can't restrain your header beams laterally. What you might be able to get away with is using your cross beams as roll beam bracing for your header beams.

 

[JoshPlumSE]

They'd have to be bolted to the beams to provide bracing. Even then, I'd do a capacity and stiffness check per AISC.... Honestly, I usually ignore the capacity and stiffness checks when it's a real diaphragm or steel beams doing the bracing. I just assume they're okay..... But, I'm not comfortable making that assumption with wood planks or beams.

 

[Azmarya]

Ok so actually over the cross beams is a 1 1/2" corrugated metal deck and then over the deck will be 2x8 planks for workers to walk on. I was also skeptical about wood planks bracing the cross beams, but the metal deck would brace them, correct?

 

[KootK]

Correct given a conventional installation I'd say.

 

[BridgeSmith]

We don't assume the corrugated decking pans to provide bracing to our bridge girders. Granted, they're probably much larger than your beams, but I wouldn't want to stake someone's life or my license on it, in any case.

First questions are do you need bracing to prevent LTB, and if you do, how many brace points do you need?

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Enable]

IIRC the Second Narrows Bridge failure was partially due to assumed restraint of a girder via formwork/slab friction during construction. Relying on friction to provide bracing is not something that should be done without an incredible amount of care. I wouldn't do it if there was any reasonable alternative, and even if there was no reasonable alterative, I'd probably still not do it.