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Vulcraft composite VL deck vs shear studs

Vulcraft composite VL deck vs shear studs

Vulcraft composite VL deck vs shear studs

(OP)
Hello,

I have successfully used Vulcraft 2VL & 2VLI composite decks over steel joists for floor framing systems over the past 10years. One of my colleagues is saying it's better to use shear studs on steel beams instead. Personally, I feel like it will be expensive to weld the studs for two to three story buildings. Can we just use Vulcraft VL composite deck on steel beams provided that we specify the puddle welds? I've always felt like using the composite deck (VL or VLI) with specific puddle welds is enough for partial composite action after checking the requirements.

Note, my floors are always 5.5" total thickness.

Thanks.

RE: Vulcraft composite VL deck vs shear studs

You use composite deck with no shear studs and develope partial composite action between the steel beams and concrete slab? What % of fully composite action do you develope and what code are you using?

RE: Vulcraft composite VL deck vs shear studs

(OP)
Less than 10%. Steel beams depth is not an issue. My colleague came from a firm where they often do high rise buildings so I understand the benefit of using full composite floor systems. Our local contractors (being working in the area for 10 years) will certainly "screw up" by placing studs in wrong places etc.. so I usually use Vulcraft VL deck (composite with the concrete) on steel beams/joists for easy installation.

RE: Vulcraft composite VL deck vs shear studs

Composite deck and composite beams are different things entirely.

RE: Vulcraft composite VL deck vs shear studs

I am unaware of any code provision that allows composite action to be considered with puddle welds as the only shear transfer mechanism. The welds get the shear into the deck, what gets it into the concrete? Friction?

Don't be afraid of shear studs. I can only speak to the areas I've worked, but composite steel construction is THE preferred and most common method for steel buildings. You need a detail that explains how the shear studs should be laid out, and then it is something the contractor should be able to easily handle.

Are you saying that you use concrete on steel deck supported by open-web steel joists as your default floor framing system? I acknowledge that there are certain applications a system like that makes sense, but that would be unusual to use all the time.

RE: Vulcraft composite VL deck vs shear studs

(OP)
Thank you all.
I have designed composite floor system in the past (some 15 years ago in Houston-Austin area) before I joined this small local firm (in a small city in Wyoming). The contractors here always ask us to find alternatives to our design to fit their knowledge, which is fine with me because the construction cost is reasonable. I was telling my new colleague that I don't see any difference in using composite deck on steel joists vs. on steel beams provided that I am not designing composite floor systems.
Also, our firm work on buildings between 2 to 3-story.

RE: Vulcraft composite VL deck vs shear studs

Yes, certainly you can use composite deck without using shear studs; just don't design the beam for any composite action! In that scenario it is simply a regular steel beam and the concrete acts separately, even though it's on a a composite deck. See what Hokie66 said.

What makes the Vulcraft deck "composite" is that it has interacting lugs that allow it to engage the concrete so that the deck and concrete act together. But getting the beam and concrete to act together requires shear studs.

RE: Vulcraft composite VL deck vs shear studs

I wonder what the savings actually are using shear studs when you consider the cost of the design, studs, stud welding and increased difficulty installing the metal deck. I guess it depends on the spans and size of the building. I personally have never used them because most of my buildings are small enough not to justify it.

RE: Vulcraft composite VL deck vs shear studs

Excel, there can be considerable material savings, enough so, apparently, to make up for the additional labor, judging by the system's widespread acceptance in many places. (I'm very bad at cost estimating so that's really my only basis for saying that.) But attaching the studs doesn't take that much effort as they simply "shoot" them onto the beam with an electric welding gun.

One thing to be aware of, though, with steel-concrete composite systems is that they can be particularly susceptible to vibration. I think that's a function of how thin the slab can be made to be. It's something to watch out for.

RE: Vulcraft composite VL deck vs shear studs

Excel:

The savings comes in that the beam supports the wet mud and a construction load of about 20 psf, preferably unshored, but the presence of the studs supports the additional live load with no more steel.

Mike McCann
MMC Engineering

RE: Vulcraft composite VL deck vs shear studs

I agree it likely makes sense on a large building but may not on small building. It is design, fabrication and installation labor costs that typically trump material costs. Don't they have to do on-site testing of random shear studs? Another cost that can be more easily spread out over a large building. Also, I wonder how much additional the metal deck installer is charging to burn holes for the studs?

RE: Vulcraft composite VL deck vs shear studs

The studs can actually be shot right through the metal deck. I'm not advocating for or against the system, by the way; I'm just discussing it.

RE: Vulcraft composite VL deck vs shear studs

Excel:

You said "to burn holes for the studs"... Really a non-issue here...

In that the studs are always welded to the steel beams at the bottom of the flutes in the deck, and the stud gun welds through the deck to the steel beam below, no cutting of the deck is needed. It is an automatic process.

Mike McCann
MMC Engineering

RE: Vulcraft composite VL deck vs shear studs

The rule of thumb I use is that the material/labor cost of each shear stud is roughly equal to 10 pounds of steel. If studs result is a reduction of the beam size, they're usually worth it. I find that serviceability concerns usually control the design over strength for the composite systems I design. In our office, it is rare to NOT use composite beams. The concrete is there already, why not use it for the structure? It's just dead weight otherwise.

RE: Vulcraft composite VL deck vs shear studs

I have only cursory knowledge of the vulcraft composite joists and how they achieve shear transfer. But, there were a couple of other systems (Hambro and Vescom) that relied on a deformed top chord or such. It seemed to me a reasonable way to ensure good shear transfer.

I'm not sure that any of these systems has gotten all that much traction in the industry. So, my guess is that there must be SOME reason for that. Maybe they don't offer great cost savings, maybe they don't perform as well as promised, or maybe they're just a pain to work with (for either the engineer or the contractor).

Personally, I'm keeping my eye out on these systems as they would seem to be quite promising. I just would like to get more feedback (positive or negative) from more engineers that are using them.

RE: Vulcraft composite VL deck vs shear studs

Interesting, I did not know thru were installed thru the deck.
@Steelion, so you are saying if the studs are 12" O.C. you are saving 10 PLF in beam weight?

RE: Vulcraft composite VL deck vs shear studs

Excel, no, what I meant was as a rough order of magnitude cost estimate to determine if composite construction will be the most economical system for your floor, compare non-composite steel weight to composite (steel weight + 10 pounds/stud X quantity of studs). The cost of one installed stud is roughly equivalent to the cost of 10 pounds of installed steel beam.

Example: 30 foot span:

Non-composite: W18x35 required. Weight = 35PLF X 30 FT = 1050#
Composite: W16x26 with 14 studs required. Equivalent Weight = 26PLF X 30 FT + 14 STUDS X 10 LB/STUD = 920#.

RE: Vulcraft composite VL deck vs shear studs

(OP)
Thank you all with your comments.
The building I am talking is 3-story office building, each floor has about 6,000 sq.ft. Since the contractors that always work on our projects have never seen us designed composite floor systems, I think i would rather use the composite deck on steel beams. With this I can still get the 1H fire rated the architect requires.

Thanks.

RE: Vulcraft composite VL deck vs shear studs

Kodstruct:
I agree with Steellion’s approach too. If the conc. is already there, why not use it to your advantage, assuming it is cost effective. Why not talk to a couple of your local contractor friends and see what they would think of the idea of shooting studs from above, and through the deck? Bring them some of the appropriate stud welding literature, and explain the potential advantages. What do they think their costs and difficulties would be, could you save enough steel, in the beams to make up for their extra costs? And, of course, your extra fee and extra effort should be included in that cost and serviceability study. There isn’t anything wrong with stretching the capabilities of your contractors, particularly when you make them part of that process. Just don’t spring it on them, if they’ve never done it before. That would just fulfill your negative prophecy.

RE: Vulcraft composite VL deck vs shear studs

(OP)
Agreed "dhengr". I will be working on two new office buildings in the next 3 months. I think I will go this route and explain the advantages of using composite floors.
This current project goes out at the end of the month, so i will use non-composite for it in the meantime.

RE: Vulcraft composite VL deck vs shear studs

I posed the stud economics question in a previous thread. The conclusion there was that, for smaller projects, it's got more to do with mob/demob costs of the stud welding equipment. The rule of thumb that the community kindly provided to me was that, if there's going to be at least 1000 studs on the project, it's probably worth it. I always seem to wind up having about 14 stud either end of my composite beams, give or take. I've taken to just multiplying the number of beams by 28 and comparing the sum to 1000. It actually takes a fairly small project (<35 longer span floor beams) for me to come to the conclusion that studs don't make sense.

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

RE: Vulcraft composite VL deck vs shear studs

Just be sure to check vibration per Archie264's comment above.

RE: Vulcraft composite VL deck vs shear studs

I have questioned the used of composite beams before in the past. I have even given a few scenarios to fabricators to price to see which system is cheaper, a composite steel beam system of a open-web steel joist system. To my surprise, they always come back and say that a open-web steel joist system is cheaper than the composite steel beam system. These are usually for smaller projects (3 stories or less) and do not include the costs associated with fireproofing.

If height is not an issue and the project is small, why not investigate an open-web steel joist system? We usually use joists spaced at 2'-6" o.c. with 9/16" form deck that supports a 3-1/2" to 4-1/2" thick slab.

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