1930's cast-in-place concrete reinforcing

[BubbaJ]

I am currently working on a project where a department store has been rennovated to meet the needs of a more industrial business. The floor framing system consists of cast-in-place concrete on 14" deep steel joists at 17" OC. There is no steel deck, only "chain male" looking reinforcing over steel straps which sit on and are transverse to the joists. A core is currently being done to determing the slab thickness and if there is any wire or rod reinforcing embedded in the slab.

Does anyone have experience with or know the history of this type of construction? We are looking to reinforce the floor for additional loading. However, at this point I don't know what it is that I would be analyzing.

Thanks.

 

[archeng59]

I worked on an old building with 2nd floor construction similar to what you describe. the expanded metal mesh was used with paper to create a temporary form, based on what I could see and find out. The paper had mostly deteriorated and was gone except for a few scraps here and there. I requested testing to determine size & location of reinforcing, which revealed square 1/4" bars each way spaced at approx. 16" o.c. The bars were about 1/2" (clear) above the expanded metal. Since an elevator was being added, a sample of the rebar was tested to find out it had an average strength of 33 ksi. The concrete compressive strength was about 1800 psi. the second floor area checked out ok for an office space.

curious to know the results of your tests.

 

[BubbaJ]

Thank you for your insight. As you noted, I am sure this system will support "office" type loads. Unfortunately, the owner would like to run pallet jack traffic over this area. If we cannot sufficiently determine the strength of the floor and framing to make conservative reinforcement of the system, there has been talk of removing this area of the floor and replacing with an adequate system. To make things more interesting, the mechanical room and boilers are directly below.
If we are able to determine otherwise, I will be sure to post.

 

[jike]

"Concrete Engineer's Handbook" by Hool & Johnson, published in 1918, show many different types of mesh, expanded metal and other types of fabric that were common during that era.

Some of the names are Welded Wire Fabric, Triangle-Mesh Wire Fabric, Unit Wire Fabric, Lock-woven Steel Fabric, Wisco Reinforcing Mesh, Expanded Metal, Steelcrete, Kahn Road Mesh, Corr-X-Metal, Econo, GF Expanded Metal, Rib Metal, Self-centering Fabrics, Hy-Rib, Corr-Mesh, Chanelath, Ribplex and Dovetailed Corrugated Sheets.

There are a couple of tables that give net sectional area per foot of width for some products. No info. on loading or strength.

If you post of sketch with dimensions and configuration, I will try to help you identify it.

 

[BubbaJ]

I have a photo, I will try to post it.

Ok, I give up, how do add a photo to a post?

Shanna

 

[BubbaJ]

Still can't figure out how to post a picture.

It has a herringbone look to it.

Shanna

 

[SlideRuleEra]

sduggan - To display an image, it must be hosted on a web server. I you don't have access to a server, email the photo to me (address on my website, link below) and I'll put it up on a free site and show it here.

http://www.SlideRuleEra.net

 

[BubbaJ]

Here is the link to the photo.

http://www.morning-starstudio.com/downloads/P9260109.JPG

Thanks.

 

[jike]

It looks like it is expanded metal with cold drawn or cold formed steel ribs. These were generally all cut and drawn from the same sheet in widths up to 48 in. and lengths to 12 feet. Spacing of the ribs was 4 to 8 in. Height of ribs varied from 3/8" to 1 1/2". Products that resemble this configuration had names such as "Self-Sentering", "Channelath", "Hy-rib" or "Ribplex" These were all companies in the midwest (Ohio, Michigan and Illinois).

I have no load tables for any of these products. If you can determine a steel area per foot of width and a strength, you may be able to calculate an approximate load capacity. The other option would be to load test an area.

 

[BubbaJ]

Thanks jike.

It appears that this type of product is still being manufactured and being used. However, I have not been able to obtain any technical information, even though product literature says it can be used as reinforcing for floor and roof slabs. (One technical support person I talked to denied this.)
Architectural Graphic Standards lists a 4#/SY lath requirement for this type of construction. I will start with that.

 

[archeng59]

jike,

where did you get the information you describe? in the handbook you posted earlier? was the expanded metal and ribs intended to act as a temporary form only, or did the expanded metal & ribs provide some strength for the slab?

did you get a copy of the handbook from ebay or elsewhere? sounds like a good reference source for older buildings.

 

[jike]

I did get the info. from the Hool & Johnson Book that I mentioned. It is a great reference and I have had it for years. I got it from a retiring engineer when I was young (and now I am close to retirement). You might be interested in how to design or analyze 3 way and 4 way slabs, SMI slabs and my personal favorite: why Working Strength is better than Ultimate Strength for designing slabs.

This plus others (Hool & Kinne) are extremely valuable resources for anyone working with older buildings. I recommend searching eBay or used book stores for those titles or authors.

I would assume that the mesh works like reinforcing for the condition described previously.

 

[archeng59]

thanks. I have several old reference books, but that isn't one of them.