Welded Wire Fabric Strength 1

[keyPitsimplE]

I am designing residential concrete walkway planking that spans between 2 p.t. wood beams. These panels will be 2 to 3" thick, 16" to 24" wide and span about 4'-6" c-c of beams. The builder wants to form them on site (yes, we talked about all of the quality control issues - he is a very conscientious builder) and use WWF sheets for the reinforcing.

The problem I am having is finding good info on WWF. Local suppliers ONLY carry galv. 4x4-W1.4 for fencing/deck railing OR 6x6-W1.4 plain for slabs on grade. They also do not know the grade of steel. Guesses vary from 36ksi to 80 ksi. Getting other sizes requires very large orders, too big for this job. I'm also reading conflicting reports online about WWFabric and WWMesh being different, with Fabric being structural and Mesh non-structural.

We want to make the planks as light as possible, using normal wt. concrete. The reinforcing size and grade has a huge affect on how thin I can make them. The builder gave me an old detail from another job showing 2.25" thick 24" wide planks spanning 3'-2" c-c of beams plank with 4x4-W1.4 WWF in the center. He wants to approximate this design, knowing it will be a little heavier duty for 4'-6" span.

Is there any problem using the galv. WWF as concrete reinforcing? I know it will be pricier, but at least it wont have rust on it to start the pop-out process and I'm getting 50% more steel per LF. I would also love to verify that it commonly comes in 80ksi.

Any help?

Thanks,

 

[Ron]

You likely won't be able to get sheets of WWF in small quantities. Rolled WWF will likely not be placed properly to give you adequate reinforcing for bending stresses. Since this is an "elevated" walkway, it would typically be designed for about 100 psf. With WWF alone, you'll likely be deficient in steel area for reinforcing.

There is no difference in WWF and WWM...just terminology.

I would also not worry about galvanizing. Proper cover and density of the concrete will protect the rebar adequately.

Use conventional reinforcing. The fencing wire should not be used for reinforcing concrete.

 

[Splitrings]

Go to the WRI website at

http://www.wirereinforcementinstitute.org.

ASTM A185 lists two strengths; 56 & 65 ksi for smooth WWF.

I would check with a local steel supplier. My supplier in the state of Vermont stocks 6x6 W6 in 5'x10' sheets. It has a steel area of 0.12 si per sf.

 

[a2mfk]

Does your code allow concrete to be supported by wood?

Also, why not use stay in place steel decking as a composite form (solve your problems)? Because this will be exposed?

 

[TXStructural]

Most reinforcing bar fabricators stock welded wire reinforcement as a matter of course. A fabricator will know the grades and sizes, and should sell you the quantity you need. DO NOT rely on the local chain retailer/lumber yard - some of them actually sell ungraded rebar and wire, which do not comply with ASTM's or other structural building code requirements.

The current ASTM for uncoated steel wire is:
A1064/A1064M – 10 Standard Specification for Steel Wire and Welded Wire Reinforcement, Plain and Deformed, for Concrete
(This replaced and consolidated the prior separate specs for plain and deformed.)

If these panels are exposed to weather, be sure you satisfy the ACI minimum cover requirements for protection, as well as the other structural needs. ACI minimum thickness for deflection is L/20 (simple spans) (2.7 inches for 54" span) unless you calc deflections.

Based on the previous build you mention, the moment demand will be at about double based only on the increased span (38" v 54") and uniform loading. When point loading and your 16" width is considered, the moment demand and stress in the reinforcement is significantly higher.

Consider lightweight concrete, composite deck (if it is indoors), and/or a thicker section.

 

[purewater1]

Fabricator's of this welded and woven wire mesh material will know exactly what you are looking for and how strong each material will be. In the past, I have called on Belleville Wire Cloth and they can usually supply the right information.

They supply material that ranges from aerospace grade to your standard fence-strength wire cloth and wire mesh.

http://www.bwire.com/

Call them up and they will be able to fill you in on the specifications, strength, and other propertied of wire and wire cloth/mesh material.

 

[hokie66]

You should follow TXStructural's advice. Trying to get too thin with concrete walkway panels can only lead to grief later on, especially if not done in a precasting plant.