Unbraced Length Question 1

[Bammer25]

Designing a simple table top steel frame for a residential 2 story wood cabin to sit on with "stilts" underneath (steep hill in mountain).

Plan view footprint is 28'x28'. Perimeter steel beams on all 4 sides.

Would you consider the floor joists running perpendicularly to supply top flange restraint? I believe it does, but I hate to make that mistake (difference between a 2' UNBL and 28' is a hell of a beam. I will probably throw in some bracing as well, but mainly talking about what I get out of the floor joists.

 

[1503-44]

Given a reasonable connection, I'd think so.

 

[human909]

I sometimes find it beneficial to provide an independent set of bracing rather than fretting about the suitable connections required. It depends on you circumstances, it is unclear what your secondary spanning members are beyond the perimeter. Mind you I don't do much residential so feel free to ignore my input.

 

[BAretired]

Joists by themselves don't provide lateral bracing. Joists held rigid by floor deck do. Presumably you have deck, so the beam would normally be considered laterally braced.

Can't say the same for the "stilts", though.

BA

 

[Bammer25]

The joists are 2x4 trusses, standard 24” deep, and will have 3/4 plywood sheathing on top. The joists will bear on the steel beam. I have not thought of the connection detail between the wood and the steel.

 

[BAretired]

The easiest connection is a wood nailer bolted to the beam. Joists are usually toe-nailed to the nailer, but there are sturdier connections available if you prefer.

BA

 

[Bammer25]

Do mixed materials matter? Paint the beam or galvanize? I would think PT would be bad for steel

 

[OldDawgNewTricks]

Concur with BAretired. But I often prefer connecting the nailer to the beam with welded threaded studs rather than bolts depending on things like the beam demand/capacity ratio, fabricator capability, etc. And I would prefer framing angles to toenail connections.

Hot dip galvanized or painted would depend on the environmental exposure conditions.

 

[Bammer25]

Thanks guys. This is east Tennessee in the mountains. Cold winters as hot summers. Nowhere near salt water