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40 ksi or 60 ksi rebar

40 ksi or 60 ksi rebar

cl220

(Civil/Environmental)

(OP)

5 Sep 12 08:20

Is there a mojor cost difference between the two grades of rebar?

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RE: 40 ksi or 60 ksi rebar

dik

(Structural)

5 Sep 12 08:39

Other than strength and composition not a lot. Grade 60 tends to be less ductile, but is most common for both main rfg and stirrups. The metallurgy for grade 60 has improved so that they aren't as 'brittle' and I haven't seen one 'break' for decades. About 40 years ago, I dropped a grade 60 stirrup in the winter and it broke into two parts after it hit the ground... some engineers still don't like using grade 60 for stirrups.

Dik

RE: 40 ksi or 60 ksi rebar

cl220

(Civil/Environmental)

(OP)

5 Sep 12 08:48

I am looking at switching our design process from grade 40 to 60. It would be mainly used just on bottom mat rebar in slab on grade construction. Previously they have always specified 40, but I thought it may be worth switching to 60 to take some of the steel requirement out of the foundation. I am trying to look at the cost difference between the 2 grades oppesed to the labor to assemble the additional steel.

RE: 40 ksi or 60 ksi rebar

kylesito

(Structural)

5 Sep 12 09:03

I don't know the exact cost figures or cost indexes, but I do not think the cost is significant anymore to worry about.

We have always specified 60 ksi bar over 40 and have never ran into any cost issues with it. Several contractors (who normally complain about every cost we put into the job) have also never taken issue with this specification.I don't know the exact cost figures or cost indexes, but I do not think the cost is significant anymore to worry about.

PE, SE
Eastern United States

"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
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RE: 40 ksi or 60 ksi rebar

frv

(Structural)

5 Sep 12 09:07

I thought they didn't even make 40 ksi rebar anymore. As far as I know (talking to some older engineers in the office), 60 ksi has been predominantly (if not exclusively) used for decades.

RE: 40 ksi or 60 ksi rebar

cl220

(Civil/Environmental)

(OP)

5 Sep 12 09:25

I am going off of old specs from the 80's that we still use. I am trying to update evrything. It sounds like I should start specifying out 60. Thnaks for the responses. It is helpful.

RE: 40 ksi or 60 ksi rebar

msquared48

(Structural)

5 Sep 12 10:13

For special details where a member either has to be field bent or field welded, I spec Grade 40. Otherwise Grade 60 everywhere else.

Mike McCann
MMC Engineering
http://mmcengineering.tripod.com

RE: 40 ksi or 60 ksi rebar

MiketheEngineer

(Structural)

5 Sep 12 10:37

1. Pick up that 2,000 lb. and call a vendor
2. Haven't seen 40 KSI called out for many years.

RE: 40 ksi or 60 ksi rebar

frv

(Structural)

5 Sep 12 10:45

Mike.. the book has gone the way of the 40 ksi rebar. If they're not online, they don't exist.

RE: 40 ksi or 60 ksi rebar

msquared48

(Structural)

5 Sep 12 12:54

They still exist to a lawyer...

Mike McCann
MMC Engineering
http://mmcengineering.tripod.com

RE: 40 ksi or 60 ksi rebar

BAretired

(Structural)

5 Sep 12 13:20

I checked with two suppliers in Edmonton, Alberta. They sell only Grade 400 (Metric) which is roughly equivalent to Grade 60 (Imperial). You cannot buy Grade 40 rebar from these two suppliers, even for stirrups or ties, but it may be available elsewhere.

BA

RE: 40 ksi or 60 ksi rebar

MiketheEngineer

(Structural)

5 Sep 12 13:44

While I find the Net to be an amazing wealth of info - voice to voice or eyeball to eyeball will often get you much further down the path you are pursuing. And yes - I am an old fart - almost 60 - but I still do VB programming and structural engineering!!

Xingtai Steel contains other products and information you need, so please check it out.

RE: 40 ksi or 60 ksi rebar

frv

(Structural)

5 Sep 12 13:52

Mike.. what I meant was that it is orders of magnitude faster to google a company's name than to pull out a book. I'm much younger than you, I'm sure, but I too prefer to talk to someone on the . I just look up the number online.

RE: 40 ksi or 60 ksi rebar

MiketheEngineer

(Structural)

5 Sep 12 13:58

It GREAT for that - no doubt!!!!

RE: 40 ksi or 60 ksi rebar

hokie66

(Structural)

5 Sep 12 22:14

In Australia, the only market for the lower strength, higher ductility, more easily site bent reinforcement is for swimming pools. Otherwise, our standard grade is now 500 MPa, or about 70 ksi.

RE: 40 ksi or 60 ksi rebar

Walterke

(Industrial)

6 Sep 12 07:39

@frv: read mike's initial post again, I don't think he mentioned a book.

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RE: 40 ksi or 60 ksi rebar

frv

(Structural)

6 Sep 12 09:32

You're right.. I completed that phrase in my mind.

RE: 40 ksi or 60 ksi rebar

focuseng

(Structural)

6 Sep 12 12:59

On topic: I have been requested to use 40ksi bar to save money on ICF walls from a specialty ICF contractor. I don't know if they buy stock by the train car load or what but 1) it is still available (subject to market) 2) there apparently is a price difference to some people (maybe labor only? I know they preferred lots of small bar vs. less big bar)

To the OP: Please post the answer you find after you call.

Off topic: I think Mikes point is that you should get a quote from a real person/entity who's job it is to happily sell you some steel and ACTUALLY WANTS to tell you because of this. The is the easiest way to do this after you found the #. Use google or the book (which ever your preference) to get the # and call a real person who already knows the answer because they have the price chart in front of them. And, FWIW, or googling is a good way to NOT establish a real relationship/contact/business referral when compared to speaking to a real person. I have never seen a market price chart for commodity building materials online -EVER, nor would I trust it if I did. And... Nothing can beat a call for speed when you want an answer for something like this. Sorry, Rant: -OFF-On topic: I have been requested to use 40ksi bar to save money on ICF walls from a specialty ICF contractor. I don't know if they buy stock by the train car load or what but 1) it is still available (subject to market) 2) there apparently is a price difference to some people (maybe labor only? I know they preferred lots of small bar vs. less big bar)To the OP: Please post the answer you find after you call.

______________
MAP

RE: 40 ksi or 60 ksi rebar

woodman88

(Structural)

6 Sep 12 17:21

Per Structuremag "Most deformed reinforcing steel used in cast-in-place concrete construction today is ASTM A615 Grade 60 reinforcing steel." You can see the artical at http://www.structuremag.org/article.aspx?articleID...

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

RE: 40 ksi or 60 ksi rebar

focuseng

(Structural)

7 Sep 12 13:11

Thanks Garth for the article. The section on cost was interesting even though it was comparing 75ksi to 60ksi (not 40ksi). Material cost was increased 2% but the required material was decreased by 20%.

______________
MAP

RE: 40 ksi or 60 ksi rebar

FSS

(Structural)

10 Sep 12 17:27

Grade 40 is still commonly used in residentiall construction, and is probably what you get in Lowes/Home Depot type stores.

RE: 40 ksi or 60 ksi rebar

Gumpmaster

(Structural)

12 Sep 12 16:51

I'd question that you can buy 40ksi in most of the US, as several have previously said. Even rebar that's labled as 40ksi probably still meets the requirements for 60ksi.

I conducted testing on mockups of old bridges. We had to order a special heat of 40ksi steel from the mill (only the stirrups were 40ksi) as no suppliers or mills in the whole state had 40ksi steel. In our material testing, most of the "40 ksi" steel yielded at ~55ksi or so, not too far below 60ksi steel.

I'd be interested if someone has actually seen a recent heat ticket for 40ksi steel and what it's actually yielded at. I think the stuff at Lowes/Home Depot is whatever is cheapest and most regionally available, so in most of the US, 60ksi (I doubt they have a heat ticket to prove it though).

RE: 40 ksi or 60 ksi rebar

2

TXStructural

(Structural)

12 Sep 12 18:32

There is still quite a bit of A615 grade 40 produced - more than I thought. Availability is very regional, and frequently you may be getting 60 ksi when you spec grade 40. It is not a true grade substitution if it still meets grade 40 ductility (ductility is the difference between the grades, other than minimum strength, and there is no upper limit on strength in A615.)

Weldability is only assured if the bar is specified ASTM A706 (in Canada it's Type W.) If I recall correctly, there once was a "weldability supplement" that certified A615 as weldable, but the current spec doesn't have one - it is all about carbon equivalent content.

If large post-yield ductility is really a primary concern (it seldom is except in seismic design), you can specify ASTM A706 Grade 60 or 80, which has higher ductility (12-14%) than A615 grade 60 (9%). In these specs, the ductility is dependent on grade and size of the bar. Stainless rebar ductility is a minimum of 20%.

ICF and swimming pool folks like lower yield strength so they can bend it in the field, often by hand. Since to bend it, you have to yield it, they like the low grade materials. This is fine for pools and artistic works. As a designer, you really should design buildings to avoid the need for that, since few field personnel will use the right bend radius, and tighter bends can not only damage the bar, but the CRSI/ACI bends assure that the concrete inside the bend does not crush and cause a bar fracture under heavy stresses. This is the failure mechanism of tighter bends in concrete. We are trying to educate ICF builders about ordering fabricated bar to make the work go faster and safer. The premium to have it fabricated is very small, and is much less expensive than field labor to bend the bar. I hand bent bar on my first ICF project, and it is not the way to go. Detail corner bars and minimum-bend, single leg stirrups to go over openings, and have them fabricated. Many fabrication shops use automatic benders that can knock out a house full of cut to length and fabricated bars very quickly.

The latest data suggests that A615 grade 60 averages 70 ksi, nominal; A615 grade 75 averages a little over 80 ksi; and A706 grade 60 averages under 70 ksi. I do not have figures for grade 40 handy, but most mills do not produce it.

The bar sold in retail centers may be non-spec, ungraded bar, so be careful with that.

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