I agree with StructuralEIT. WWR is how the industry trade group, the "Wire Reinforcement Institute", refers to the product. Here is their manual of standard practice:
WWF properly specified and installed on continuous chairs is cost effective when compared to reinforcement of deformed bars. Poor engineers specifying 6"x6"-#10x#10 deserve the results they get.
After 28 years of harping on contractors, specifying chairs, etc. and not getting it....well....I don't deserve it - so WWF doesn't get specified by me for on-grade conditions.
Our office usually calls for the WWR to be tied to #4 @ 48" ea. way. When it is something substantial (like #4 bars), chairs are usually installed which places the reinforcement at the correct location.
WWC...that's a new one for me (and pretty funny at that).
i never understood why it's so hard to get the stuff up off the ground. in my contractor days, we supported the wwf at 4' o.c. and still had someone going around during the pour pulling up the areas in between. it wasn't rocket science and didn't take that much time/effort to do.
i like to see the heavier guage stuff specified if at all. at least the industry has moved away from that rolled up crap that would tear you up if the guy on the roll end let it go after rolling out about 20' of the stuff and you were on the other end (end that the stuff rolls up toward like a wound up spring). however, it did make for some comical scenes at times (thank goodness i never saw anyone seriously hurt).
msucog,
The problem with pulling up WWC (heh) is that there is NO way to provide quality assurance that you are getting what you ask for.
The wire fabric cannot be seen, it is being stood on by the workers who have no direct control over the height of the wire in the concrete, and then step over it again to get to the next area. This is absurd and goes against everything recommended in ACI in terms of placing reinforcing in a secure fashion prior to placing concrete.
This has come up many times in this forum, but my 28 year structural engineering experience has taught me not to specify it, or detail it ever again. It does not do what they purport because it NEVER ends up where the detail drawing shows it is supposed to be.
I know there are two distinctly divided schools of thought on this one, but I will never cross the line again with this welded wire crap.
oh i agree completely. however, if supported at 4' o.c., i feel comfortable that it is "more or less" in the middle of the slab (more than if not supported that is). we core slabs all the time and 90% of the time, the wire is on the bottom (exposed on the bottom side of the core that is) because they're never supported. if the heavier guage stuff is required, at least it's too rigid to bend much under the weight of the workers when supported at close spacing. my concrete professor taught us that the wwf was just to help hold the cracks together to some degree...but absolutely shouldn't be counted on for anything else unless it is the heavy guage stuff. i definitely prefer to see reinforcing bar specified.
I've taken too many cores with the WWM/F/R located at the bottom of the slab. I spec rebar to be located with 2" top cover... works fine as long as it is chaired properly...
Just to be contrary, as is my wont, the reinforcing in a slab on ground does more good in the bottom (but not in the dirt). The applied force due to restraint is at the bottom, so that is where the crack starts.
Hokie, I disagree. The steel is more for shrinkage and temperature changes. The top of the slab releases its moisture much faster than the bottom of the slab (usually against a vapor barrier). The release of the moisture causes shrinkage in the top. Since the bottom is restrained and the top tries to move, a crack forms at the top of the slab.
In addition, who cares if a crack forms in the bottom. Nobody will ever see it. You want to control the crack dimension where it is visible (on the top).
![[idea]](/data/assets/smilies/idea.gif "[idea] [idea]")
![[lol]](/data/assets/smilies/lol.gif "[lol] [lol]")
WWC... I can't wait to use that one
