astm steel grade to support basement wall

[heypat]

The wall in my basement has cracked at the frost line and has started to bow approx 1/2". I have researched several systems to stabilize the wall and I am leaning towards a system that uses c channel anchored to footing and the ceiling rafters. The channel is pinned at the floor first then the top of the channel is pushed towards the wall via a bracket mounted between the floor rafters actually bending it to conform to the bow in the wall. This is supposed to keep pressure on the wall and eliminate any further bowing. I have a couple of estimates and given the materials and labor involved the price is way out of line, $4000.00 to install 7 pieces. Given the pricing and labor involved I am planning on doing this project myself. I have been in manufacturing / fabrication for the last 12 years and know I can install all 7 units in under 8 hours. I have been told to use carbonized steel for the c channel because of strength. My problem is there are several types of carbonized steel and I know some of it can be brittle. Can someone please suggest a ASTM # for the proper grade of carbonized steel to use for such a project. I am also curios what everyone here thinks about the actual process of stabilizing the wall.

Thank, you in advance for your suggestions and comments

Pat

 

[JAE]

Pat:
Most standard steel channels in the US are ASTM A36.

This is carbon steel (don't know of and never heard of carbonized steel). It would be found at any local steel fabrication facility in your vicinity.

The steel has a minimum yield strength of 36,000 ksi (thus the A36).

Laying a channel flat to the wall with the two flanges perpendicular to the wall may help eliminate the potential for the wall to collapse inward. However, I would expect that the inward bowing would continue a bit due to the high lateral earth pressure on the wall. By laying the channel flat, you are only getting use of the weak axis bending of the channel.

We have stabilized basement walls in the past, but used wide flange shapes to do this as they incorporate theie strong axis bending and are thus stiffer.

One of the key things you should consider is minimizing the lateral pressure on the wall (in addition to any supplementary steel strengthening). Some possibilities are reducing any ground water that gets to the soil behind the wall. This can be accomplished by ensuring that all roof drains are sent away from the wall, that the ground above quickly drains water away from your house, and that your wall has some kind of working drain system behind it - where ground water can be captured and pumped or piped away.

 

[heypat]

The salesman that came over had a piece of the channel with him. I looked like regular 4" c channel about 1/4" thick with the legs about 1 5/8" long. The pictures he showed of the installed product showed the flat of the channel against the wall with the legs facing the interior of the basement. When I called him back to inquire about the high cost he claimed they use special carbon steel thus the high cost, he called it STS-W6 Carbonated steel (maybe this is a manufacturer part number?). If I read your post correctly then standard ASTM A36 is carbon and what I am looking for. You mention using wide flange shapes in the past. Do you have a product call out for any particular channel that would be useful in my application? When I called the supplier I use at work for a quote he quoted 4" c channel with 1.647 legs at 6.25 pounds per foot, ASTM # A36. I thought this was the right stuff until the salesman mentioned the above part number. When I gave my supplier the part number the salesman gave me he never heard of it before. Is this a case of typical salesman saying whatever to get the sale?

If I can use the ASTM A36 then my material cost will only be $175.00 for the channel and I figure another $100 to $200 for miscellaneous materials, anchors, drill bits etc. This is a far cry from the $4000.00 I was quoted.

Thanks again for all of your help and comments, I really appreciate it.



Pat

 

[JAE]

Pat - no clue on the STS number - also, standard 4" channels from AISC are 4.5, 5.4 and 7.25 lbs/lf so his shape may be a custom shape for his company.

Most structural-type steel has a similar modulus of elasticity (E) that is 29,000,000 psi. This is the materials stiffness (how much it stretches under load...so his shapes and the ones from a fabricator or other shop would depend on their shape only for the job at hand.

You are probably OK in doing the work yourself...the only issue is what shape, what connection to the slab/floor and what spacing to adequately resist either the load or some level of acceptable bowing....

Here I go being a salesman, too, but you might want to hire a local structural engineer just to help you out with the concept. You might find one who would take a couple of hours to simply check out your basement and do a few calcs to give you a better handle on the layout. He'd probably charge between $65 and $100 per hour - a couple of hundred bucks might well spent money.

 

[heypat]

You don't have to sell me on a Structural Engineer. I planned on hiring one if I did the job myself (you are correct money well spent)my big concern was that the steel the salesman referred to was special and very expensive. After reading your posts I know that this is not the case. The salesman actually drew a diagram where each beam would be located. And I know exactly how they are securing the channel to the footing and the ceiling. I would still want the opinion of an engineer before I went through the trouble of doing the job; I only want to do it once. Basically all they do at the floor is mount a piece of angle iron with 2 anchors that go through the basement floor and into the footing. The channel is inserted between the angle iron and the wall with the flat of the channel against the wall. At the ceiling between the floor joists they have a bracket also made out of channel that has a jackscrew going through the center of it. They use the jackscrew to bent the channel to the contour of the wall and supply pressure against the wall. It is actually a pretty simple system and installation should not take long. Any way Thanks to your advice I will be contacting a structural engineer and installing this system myself. If you could recommend one in my area that would be great. I am located in Saint Clair Shores Michigan, just a couple miles north of the Detroit border.


Once again, thank you for your time

Pat

 

[JAE]

Try calling your local ACEC - Michigan at:

http://www.acec-mi.org

 

[boo1]

Thinking of this as an engineering problem you are installing grid strap reinforcement, designed to stabilize a foundation that have fractured or bowed due to soil pressure, water damage or other causes. Your system should use any steel, just adjust the section modulus lineariarly to the strength change.

A.C.I. #530 the maximum spacing for external reinforcement of the masonry wall, is 4ft., with a 2.5 safety factor

Consider using composites

http://www.fortressstabilization.com/whatsnew.html

Consider the problem of water intrusion too.

 

[SteveBausch]

I am investigating a fixer-upper myself, with a severely bowed wall. There are at least two systems; one as you described, and another that reminds me of roof-bolting in mines.

It's pretty simple; "deadman" plates are installed in postholes in the yard, threaded rod ties the vertical channels to the deadman.


There isn't anything special about the system, except for the profit margin. Two 40 ft walls at a total price around 5-6 thousand. I think the guy on the phone quoted seven beams per wall.

I don't mind their asking price. I assume the contractors have their dry spells, and a need to work with serious customers who truly value the effort.

I just think I can do it, myself.

Whatever the threaded rod is, or isn't, I assume it's coming from standard lengths. McMaster Carr shows all variety of threaded rod in 6 foot and 12 foot lengths. I will work with 6 foot length, 7/8" by 9 (N.C.). Will use zinc-plated, though 18-8 and other stainless is available. Can't imagine "threading the needle" over any longer distance.

Channel? Thinking of 6" channel. When I show up at the used steel yard, I would also seriously consider 5 by 5 angle.

And of course, my investigations brought me to eng-tips.com

 

[SteveBausch]

Here is an article from Journal of Light Construction. A member recommended the site, shame I failed to note their name.

http://www.jlconline.com/cgi-bin/jl...091e00c271a401e1d29063b/Product/View/9503prac

"Practical Engineering: When a Block Foundation Cracks"

Pay the three bucks to access the article, it's a bargain.

 

[boo1]

It seem the channel would be easier to load with out introducing torsional loading. I would thing the zinc plated rod would be my choice too.