wwm strength

[Mixtli]

Hi all, I posted this on the bonding and welding forum with not too many responses,

The cross joint of structural mesh shows one wire embedding into the transverse one which is the result of the electrical resistance welding, right?
I'm just wondering if there should be any concern on the reduced cross section due to this fusion. The steel on one direction will work as flexural reinforcement on tension and compression sides, and the steel in the other direction will work as temperature reinforcement.

I attached a picture for clarity.

Regard

 

[TehMightyEngineer]

Remember that stresses perpendicular to each other are not directly additive. Thus, even though the total cross-sectional area at the weld may be less than the sum of the areas of the discrete bars, the total combined stress at the weld is also not the direct sum of both stresses in each discrete bar. Wither the combined stress exceeds the resistance of the combined area of wire I do not know, but I wouldn't personally be concerned.

If you are concerned then you could make sure that such a weld meets the fabrication requirements in the specification for the fabrication of WWM, beyond that is up to you.

Maine EIT, Civil/Structural.

 

[KootK]

We're actually talking about rebar here rather than welded wire fabric, right? If so, creating brittle, fatigue prone heat affected zones at the welds is a serious issue. Considering that the fusion depth is half the diameter of the rebar, I'd say the result is junk.

Is this designated, low carbon weldable rebar? If so, that may change my answer some.

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

 

[TehMightyEngineer]

I assume this is welded wire mesh (or fabric if you prefer the term) given the title references WWM, so it's probably not rebar.

Maine EIT, Civil/Structural.

 

[KootK]

Did you check out the pic TME? That's some seriously stocky wire if it is indeed WWM. Maybe it's just a scale distortion thing in the photo. There also appear to be knurls although it's a bit tough to see with all the rust.

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

 

[TehMightyEngineer]

Yeah, that was some serious rust, I'd actually be more concerned about that than the weld.

As shown in the above picture, welded wire can and does come in some pretty large sizes. I've specified some pretty hefty stuff for precast construction before.

Maine EIT, Civil/Structural.

 

[KootK]

Huh, I wasn't aware that such a product existed. The "mesh" in the photo is really just shop welded A706 though, right?

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

 

[TehMightyEngineer]

Possibly, it's been a while since I looked at the spec for it. Typically it's 60 to 80 ksi so I don't know if A706 gets that high but I don't see why it couldn't be A706.

Maine EIT, Civil/Structural.

 

[Mixtli]

Hi Guys,
It is actually wwm,I took the picture myself.
One thing I noticed on the pic TME posted is no embedment of one bar into the other, like it was spot welded?

 

[KootK]

I noticed that too. I would have expected something more TME's pic. Do you know if the mesh is fabricated from weldable rebar (A706)? If not, I would think that the manufacturer would have had to preheat the steel before welding at the least.

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