Concrete Slabs on Metal Deck governing code
Concrete Slabs on Metal Deck governing code
(OP)
Which code or standard governs the design for the concrete strength and control joint spacing for elevated slabs on metal deck? What is the minimum strength of concrete that can be used on a composite concrete slab on metal deck? What is the criteria for depth and spacing of control joints? Is all this information in SDI, I don't have the book. Is the SDI manual worth buying? Please note references for advice.





RE: Concrete Slabs on Metal Deck governing code
Composite concrete slab on metal deck is similar but obviously affects your beam design. With a significant project, a 4000 psi mix may prove more economical than the 3000 but you'd have to do some trial designs and compare costs.
Control joints: Normally, we do not specify control joints in elevated slabs.
SDI puts out a Diaphragm Deck Manual is informative and gives you good background on diaphragm design of decks. Many of the deck suppliers put out good catalogs that summarize the info.
RE: Concrete Slabs on Metal Deck governing code
RE: Concrete Slabs on Metal Deck governing code
1. Your concrete f'c = 1800 will result in a lower composite beam capacity and affect the shear strength per shear stud connector. This should all be included in your calculations.
2. Your concrete's low strength will also result in a lower Ec which is usually given as (wc)^1.5 x 33 c sqrt(f'c) where wc is your unit weight of concrete in lb/cu. ft. and f'c is in psi. The lower Ec will result in higher deflections (n = Es / Ec will be higher and your transformed section Ixx will be lower).
The composite section is stiffer than the non-composite section, even with the low strength, but you also may be approaching the compressive strength of the concrete.
RE: Concrete Slabs on Metal Deck governing code
How do you handle misc. deck support around a rather large (say 32") concrete column in a composite slab? The column is continuous thru the floor. I get various answers on who is responsible for this material and design. Our specs & plans handles openings but I would like to make sure my package has this covered.
TW
RE: Concrete Slabs on Metal Deck governing code
I agree, it can be a gray area and sometimes is missed by not-so-bright contractors - but most of them are aware of these misc. items and include them in their bid.
RE: Concrete Slabs on Metal Deck governing code
Can a girder parallel to the metal deck span be considered as composite and designed as such? How can one consider such girder as part of the shear transfer mechanism?
RE: Concrete Slabs on Metal Deck governing code
The direction of the flutes of the deck only affect the shear stud capacity a bit (See AISC's specification for the adjustment factor).
RE: Concrete Slabs on Metal Deck governing code
I have not see any control joints or shrinkage joionts in elevated slabs. I think this is because the steel and metal deck which is tied by the composite action to the concrete all thermally expands and shrinks at the same rate. WWF, metal or fiberglass fibers that you should add for conrete shinkage. Any construction joints should be off the centers of beams and girders, so the concrete will be in compression on the top. I have seen extra reinforcement placed above girders to distribute/ minimize cracking from the filler beam end rotation.
RE: Concrete Slabs on Metal Deck governing code