Uplift load on concrete fill over form (non-composite) deck. 1

[whymrg]

I have an existing building with the roof composed from a galvanized form deck and a concrete fill. The wind uplift load is larger than the weight of the concrete. The deck is capable to resist this load. Is there any literature or data on the bonding strength between the concrete and the deck to make sure that the concrete will not be lifted from the deck? Is there any suggestions/examples on how to deal with this problem? Thank you.

 

[jayrod12]

How much concrete fill? And what kind of wind load. any reinforcing in the fill (unlikely)? did they use the composite type deck (with the little nubs to improve bond)?

 

[jayrod12]

Nevermind about the composite deck question. just re-read the title.

 

[whymrg]

The deck is 1 inch 24 gage deck and the concrete fill is 2.5 inch (3.5 inch total) light weight 4000 psi concrete with 6x6-W2.9x2.9 WWF. There is no indication that there are any studs or any other means to connect the concrete to the deck or to the joists. The buildign is in Florida and per ASCE 7-10 the wind speed (ultimate) is 150 mph. The ASD uplift is about 70 psf and the weight of the roofing and slab is about 40 psf. Any suggestions?

 

[KootK]

I suppose that you could install bolts or drive pins from the underside to positively attach the deck to the concrete. If the deck gets connected to the concrete sufficiently, is there reason to believe that the welds connecting the deck to the joists will be able to transfer the uplift that you require? For that matter, will the added weight of the joists and plenum assembly be sufficient or will you need to put the joists themselves into uplift?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[whymrg]

The deck to joist weld is OK and the joists are OK, so the issue is the fill. Thanks for the suggestion. I will try to work with it.

 

[KootK]

I'd be tempted to try something like this:

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.