Slab on Metal Deck Diaphragm, Synthetic Fibers 1

[mijowe]

I am working on a project where the builder cannot get WWF for a composite slab on metal deck and they want to use a synthetic fiber mesh as a substitute. Setting other issues aside, I cannot seem to find anything about how this would influence the deck as a diaphragm. The SDI literature assumes a minimum WWF for their tables. Has anybody found anything that discusses this?

 

[jayrod12]

Is the deck providing the diaphragm capacity or the concrete?

 

[mijowe]

Using the Steel Deck Diaphragm Desing Manual, the concrete increases the shear strength of the deck alone, so both would be working together. The Manual goes on to say that "insulating concrete" helps as well and publishes values somewhere between the deck alone and structural concrete-filled deck.

 

[phamENG]

The steel deck is the diaphragm, then. The concrete isn't adding strength directly, but rather stiffening the steel and allowing it to take more load before in plane buckling causes failure. Unless the diaphragm tables you're using specify a particular reinforcing, I wouldn't worry about it. Now, if you're using the WWR for flexural strength, the fibers usually won't work. You say a fiber mesh, so you may have something I'm not familiar with.

 

[KootK]

Rightly or wrongly, I've been assuming that fiber reinforced decks contribute to diaphragm capacity. From a non-diaphragm perspective, I believe that both WWF and fiber are there for crack control only. Logically, to the extent that crack control is required for shear capacity, I'd think that both products would be capable of doing similar jobs in preserving aggregate interlock. At the same time, I suppose that I do not know with certainty that the published shear capacities do not rely on the WWF function as true shear reinforcement. And, for that purpose, I wouldn't normally assume fiber reinforcement to be the equal of WWF or rebar.

 

[ATSE]

I do not believe non-metallic fiber is not a substitute for reinforcing steel, even WWF. In fact, in an attempt to gain even more friends, I will say that fiber is oversold and generally under-delivers. I haven't specified it in the last 20 years.
Even if the concrete over deck has cracks consistent with unreinforced slab-on-ground concrete, it is hard to believe that the diaphragm shear is measurably diminished.
However, the ER report for Nucor-Verco (the most common deck in the Western US) requires steel WWF or equal. Probably for the reasons Koot mentioned above.

 

[mijowe]

thanks for the input

 

[hokie66]

ATSE,

Best to edit out the double negative near the beginning of your post.

 

[ATSE]

hokie,
Good catch. Thank you. I meant to say, "I do not believe non-metallic fiber is not a substitute ..."
I'm not sure how to go back and edit old posts. Previously, I believe there used to be a Edit Post icon (or something similar), but I don't see it.

 

[hokie66]

ATSE,
It is down in the right corner of your post, between the Report and Delete buttons. But it goes away after a time, not sure how long.