One-way RC slab with draped wire mesh! 1

[LicensedToPEe]

I am looking at a set of plans from 1965. The structural engineer had designed a foundation plan with grade beams about 8ft apart supported on piles (nothing abnormal). The slab, however, is designed as a 4.5" one-way slab between the grade beam with reinforcement that is wire mesh in parabolic shape embeddment, i.e. mesh 3/4" from top surface over grade beams and 3/4" at midspa (draped) in a continuous parabolic fasion. Has anyone ever seen anything like this? Also, the wire mesh is designated as 312-48 WireMesh. Is anyone familiar with this notation? Any help is appreciated.

 

[bridgebuster]

Could the 312-48 be a metric designation? I'm looking a table published by the Wire Reinforcement Institute. They show various girds at 305 mm. However at this spacing the minimum wire size is MW 54 corresponding to 175.7 mm^2/m. The table does show MW48 wire using a 152 mm grid. MW48 wire is equivalent to a US W7.5 wire, Fy = 60 ksi.

 

[UcfSE]

I have heard of draping the wire mesh but never worked with it. It's probably not parabolic by the way, maybe catenary. Anywho, you have continous wire mesh that's near the bottom at midspan for positive moment and near the top over supports for negative moment. Try taking a look in steel deck catalogs, there might be some information there. I don't remember where I read about it.

 

[LicensedToPEe]

UcfSE,

you right, it is catenery, not parabolic. Good catch!

 

[JedClampett]

I have a 1968 edition of Gaylord and Gaylord, "Structural Engineering Handbook." On page 11-3, they have sizes and designations for WWF. 312-48 has bars spaced at 3 inches longitudinal and 12 inches transverse with #4 gage bars longitudinal and #8 gage transverse. Areas are .159 sq. in. per foot longitudinal and .021 sq. in. per foot transverse.

 

[LicensedToPEe]

JedClampett,

thanks a lot. I'm thankful for eng-tips more and more everyday

 

[JAE]

I have used a draped WWF in concrete pan joist structures for the slab between the joists. Usually these were what we called skip-pans where the joists were 5 to 6 feet apart. The idea was that the WWF would hang up on the joist rib longitudinal reinforcement and then drape down between the joist ribs and be chaired at the slab midspan by a 3/4" continuous chair. The concrete placement would try to drive the WWF down so there really wasn't any magic to it.