Reinforcing Metal Decks
Reinforcing Metal Decks
(OP)
I have a project where the previously installed metal decking is now under designed for the new roof loading. I am wondering if anyone has encountered this before. I'm looking for a way to increase the moment capacity.
I have a couple thoughts on how it could be done:
-Attach metal bar to the bottom chord of the panels
-Attach metal sheets to the bottom chord of the panels.
I haven't checked through the numbers completely, but i'm looking for what other people have done in the past, or some standard details from manufactures (Which I haven't been able to find).
Thanks in advance
I have a couple thoughts on how it could be done:
-Attach metal bar to the bottom chord of the panels
-Attach metal sheets to the bottom chord of the panels.
I haven't checked through the numbers completely, but i'm looking for what other people have done in the past, or some standard details from manufactures (Which I haven't been able to find).
Thanks in advance






RE: Reinforcing Metal Decks
RE: Reinforcing Metal Decks
I have many times installed new joists between existing joists to cut down the span of the deck. Joists need to be specified with a bolted mid-span splice OR one bearing end to be field installed. Also new joist must span between bridging since it will NOT generally be attached to the deck for lateral stability. Also specify no camber and Min. Moment of Inertia.
RE: Reinforcing Metal Decks
Here are some details that I developed along the way:
1) Channel deck reinforcing: Link
2) New OWSJ top chord deck connection: Link
Notes:
1) My hand sketched versions of these details were glorious. My drafters have a penchant for drawing things at too small of a scale.
2) With the channels, I did my darndest to make it constructable with long slotted bolted connections etc. They welded the crap out of all of it.
3) I'll allow a fair bit of deck overload before I'll go to all this trouble. In my opinion, the consequences of deck failure are not terribly dire.
4)Having thought about it for several months now, I've thought of two additional reinforcement strategies that might work well if the original deck worked in shear / web crippling:
4a) Use light gauge reinforcing members, similar to the channels, that do not quite make it to the OWSJ top chord.
4b) Nest new segments of deck to the underside of the existing deck. Obviously, one has to consider any junk suspended from the existing deck.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Reinforcing Metal Decks
If you elect to add new members all I would add is keep the members as light and short as reasonable. The biggest challenge for these type of jobs is working around existing mech/elec items. The problem with existing features can turn into a real problem.
If the roof membrane is old or planned to be replaced soon, it can be easier and more cost effective to merely lay down another layer if the joists are acceptable.
RE: Reinforcing Metal Decks
Good point. When I do channel (or angle) deck reinforcing as shown in Koot's sketch I generally don't weld to the existing. I actually have them make a saddle out of an angle and a piece of plate. The horizontal leg of the angle is sized to go completely over the existing joist to the other side. The piece of plate is then welded to this angle creating a saddle. No welding to existing is required therefore no paint removal is required.
The angles and channels are not getting fastened directly to the deck so there are no uplift concerns.
RE: Reinforcing Metal Decks