huangyhg

fiber vs wwf
so, without telling anyone, contractor decided to substitute fiber reinforced concrete instead of the vulcraft metal deck with concrete/6x6wwf i spec'd for a second floor. now he calls, wanting approval from yours truly so the job can proceed. i checked with vulcraft to see if the frc is an acceptable substitute, and they (understandably) have no position either way.
anyone run into this scenario before?
is the steel deck composite or non-composite deck?
non composite
manofstl,
looking beyond the obvious contractor issues you are facing, the use of steel fibers is adequate as a substitute of wwf for temperature and shrinkage reinforcing according to the may 2003 update to the steel deck institute' design guide.
"cold-drawn steel fibers meeting the criteria of astm a820, at a minimum addition rate of 25 lb/cu yd (14.8 kg/cu meter) and possessing an average residual strength of at least 80 psi (550 kpa) when tested in accordance with astm c1399, may be used as a suitable alternative to the welded wire fabric specified for temperature and shrinkage reinforcement"
if it was composite deck i would be less concerned, but as you see in the vulcraft manual, there are minimum areas of steel that are required and notes regarding when the mesh should be draped for non-composite deck.
i've never heard anything good about substituting fibers for mesh. my understanding has been to count on fibers (particularly synthetic fibers) only for increasing the aesthetic value of a slab.
steel fibers work great for temperature and shrinkage reinforcing especially for slab on grade. this is not a suprise considering that most anyone who has seen where the wwf actually ends up in almost all placements (on the bottom of the slab). i would not spec it, nor is it code approved for, a replacement for required flexural reinforcing.
my previous post is valid (as the sdi document states) for composite slabs only.
a lot depends on the reason for specifying wwf. willisv has a good reference for temperature and shrinkage. another resource, if the wwf was for structural purposes, is the wire reinforcement institute at
just check your deck design for non-composite capacity carrying the concrete. many vulcraft non-composite tables are based on using the wwf for actual concrete reinforcing. if the new use of the form deck without reinforcing is ok per the tables then the fibers may be ok structurally as the deck simply takes all the structural loading and the concrete is just a mass going along for the ride.
if the deck by itself can't take the loads without the wwf reinforcing, then you've got a problem...or rather, the contractor has a problem.
well, vulcraft's manual doesn't call it out, however, another metal deck company (csi) states in their fine print, something about reducing the tabulated loads by 10% if wwf per aci isn't used for their composite deck. to me, that implies it is essential in form deck.
chipb - how does a note about composite deck imply anything about non-composite form deck?
if there were any cylinders poured with the steel fiber mix, maybe you could use those tensile test results (steel fiber doesn't help that much in compression) to check the design of the concrete (assuming that the deck does not support anything, structurally). i have read that adding 1.5% (by volume) of steel fibers to concrete mix can increase tensile strength up to 40% and flexural strength up to %150.
if there were no cylinders poured, but you knew the type of fibers used and the amount, you could possibly determine a ball-park strength of the concrete and use those numbers to check the design.

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