Vulcraft Composite Deck 1

[mijowe]

I recently received a Vulcraft deck catalog and noticed that the allowable super imposed Live Load listed for their deck are a lot lower than some of the other catalogs that I have.

For instance: 3" 20 gage deck, 6.25" LW slab for a 12'-0" clear span:

Vulcraft: 80psf

USD: 185psf 1 stud per foot
115psf no studs

The USD manual that i have is older and actually has 33 ksi steel while the Vulcraft is using 50, and to top it off the unshored spans for Vulcraft are actually higher than those for USD.

Has anybody ever noticed this?

 

[Hokie93]

I contacted Vulcraft in 2008 after noticing the same situation. The response from Vulcraft was that the embossments on their composite deck was less 'aggressive' than the USD embossments. Also according to Vulcraft, their composite deck capacity is nearly identical to the published USD values when shear studs are present on the steel beams and girders. Unfortunately, Vulcraft doesn't publish the data to back up this claim (or at least it wasn't included in their 2008 deck catalog - the most recent catalog I have).

 

[JAE]

That is consistent with the fact that composite metal deck's primary limit state is shear-bond failure between deck and concrete - so that a difference in embossments would certainly make a difference.

 

[mijowe]

Thanks for the info, was going to call Vulcraft on Monday.

Hard to understand why they would not emboss their deck to get full capacity.

They do provide the standard strength determination equations in their manual, but they do not appear to have any information on how to reduce the capacity for their bonding. They also do not provide Sc or phi Mno for verifying their values.

I have always put minimum required deck properties on my drawings, I, S, gage, etc, and expected to get a deck that works. I have never thought to exclude a deck manufacturer.

 

[JedClampett]

When I use a composite deck, I never trust those buttons or deformations or embossments or whatever. I was trained that way in 1976 and I've never changed. We used reinforcement with composite deck as a belt and suspenders approach. And then we ignored the belt.
A lot of the engineers I work with now from many different backgrounds, do it the exactly same way. I guess the word got out. Maybe the problem you're seeing is a symptom of the bigger issue. If different manufacturers of a commodity, like metal deck, have vastly different capacities there's something wrong.

 

[JAE]

Hmmm - I don't know about that Jed. I did some lab/research work years ago on composite decks. The variability of the failure mode (again - shear bond failure) was pretty tight.

We were developing a phi factor for the use of LRFD with these decks and wavered between 0.9 and 0.85 because the failure wasn't always sudden (like concrete shear failure) and the variability was low.

But ya gotta do what you deem appropriate.