Steel deck as lateral bracing
Steel deck as lateral bracing
(OP)
Hi,
When you have beam parallel to joists, there is no lateral support between the columns except the steel deck.
Do you use steel deck as effective lateral support to the top flange of the beam?
Which equation do you use?
Thanks
When you have beam parallel to joists, there is no lateral support between the columns except the steel deck.
Do you use steel deck as effective lateral support to the top flange of the beam?
Which equation do you use?
Thanks






RE: Steel deck as lateral bracing
I believe you'll need eqs A-6-7 and A-6-8 of AISC 13
RE: Steel deck as lateral bracing
RE: Steel deck as lateral bracing
RE: Steel deck as lateral bracing
If the deck has a concrete infill - a typical floor beam - then, once the concrete hardens, the direction of the deck would become immaterial to the lateral support of the top flange. The flange would be continouously laterally supported, assuming composite action.
If it is a typical roof beam with no concrete infill, then I agree with the comments above, assuming you are not using decking less than 1.5 " in thickness and 20 or 22 gage. I would not rely on 3/4" Formdeck.
Mike McCann
McCann Engineering
RE: Steel deck as lateral bracing
In a X bracing under seismic loads, the horizontal beam is in compression or in tension. Do you still use the steel deck (without concrete infill) as a lateral support on the top flange? In this case, the bottom flange of the beam is only laterally supported at his supports.
RE: Steel deck as lateral bracing
Bottom flange - could brace with purlins, but don't forget the effect of the moment inflection point that could be considered a lateral brace point for the bottom flange too.
Mike McCann
McCann Engineering
RE: Steel deck as lateral bracing
Though if you brace near the inflection point you can substantially reduce the moment that must be carried by the much longer unbraced length.
RE: Steel deck as lateral bracing
RE: Steel deck as lateral bracing
DaveAtkins
RE: Steel deck as lateral bracing
RE: Steel deck as lateral bracing
Unless you can show (using AISC 13th Ed. Appendix 6) that the deck can take the brace force in compression, I would say forget it. Even if you can show it does, I wouldn't count on it.
RE: Steel deck as lateral bracing
The point is they recognize some lack of stiffness of the diaphragm in that direction for functioning as a tie/strut, I do not know how this equates to bracing beams with the same parallel deck. It likely works for most all cases but I am sure there are some that it wouldn't. For instance, a large composite girder with wet concrete and 22 gauge form deck running parallel to it.
RE: Steel deck as lateral bracing
The accordian shape of the deck is not going to resist a substantial amount of lateral force applied perpendicular to the flutes. Like the accordian, press on the sides and it collapses.
RE: Steel deck as lateral bracing
Local buckling of the deck in the area of the beam is what I would worry about, whether it is part of a diaphragm or not. But just based on the number of beams that have been assumed braced this way over the years, my idea is that deck running parallel to a beam works well enough as a brace in (most} cases.
RE: Steel deck as lateral bracing
RE: Steel deck as lateral bracing
For brace frame beam buckling restraint during axial compression, I dont rely on the deck and rather frame interior infill beams perpendicular to the brace. I connect the two with a detail that also restrains the bottom flange.
RE: Steel deck as lateral bracing
I would use an attached deck (in either direction) to brace the member acting as a beam, but would provide some other lateral support to the member when acting as part of a frame. For metal deck bracing a beam see thread507-186125: Steel beam and metal deck unbraced length.