OT (kinda): Highway building code question

I know, I know, alt.building.construction, but I've found that y'all know as much about this stuff as those folks, and I feel like nobody who reads this group would possibly have the gall to post a reply on point unless they knew for a flat-ass outright fact what they were talking about.
Background: A friend of mine is working for the Army who is doing a construction project for the Border Patrol in southern California. This project mainly involves building box culverts, runoff slabs and road beds. According to my buddy, these structures are built to interstate highway specifications, even though a 5/4 ton pickup is the heaviest vehicle these roads will probably ever see.
The Plot Thickens: A Chief Warrant Officer (a surveyor by trade) told this crew, who was putting in a steel rebar mat, that only every third joint be tied together. This raised some discussion among members of the crew, one of which swore that OSHA required that every joint be tied. This, to me, sounds like a dumb-ass thing to say. ANSI maybe, but not OSHA. Further, he swore that the joints could not be welded, as the welding process weakens the steel. Also completely ridiculous as far as I can tell, in the context of the concrete system.
I told him (my buddy) that local building codes vary (and are all subject to the building inspector) but the only reason rebar gets tied or welded together in a concrete system is to hold it in place until the 'crete gets poured over it. 8 hours after the pour, that little piece of wire has done its job. I further told him that perhaps welding rebar may weaken the steel at that point, but does not have a significant effect on the overall strength of the concrete system.
The Question Itself: Is there an online (or other) resource that describes the building codes for interstate highways? I DAGS and wound up with the UBC (Uniform Building Code) and hundreds of places online that would sell me a copy for about $200, but I'm not willing to pay that to prove I'm right about this. All of my knowledge comes from old-timers and the not-infinitesimal experiences I've had in dealing with concrete and concrete contractors.
Thanks, y'all.
-Phil Crow
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snipped-for-privacy@yahoo.com wrote:
snip

I've been pouring slabs on a rate job lately, and we only tie (most) corners and where the rebar sags too much. Given the relatively light gauge of tie-wire I typically see used, and the relative lack of tightening thereof, I doubt that the ties make any structural difference.
Were it a slab of my own, I'd tie each joint - and well.
As far as welding goes, I highly doubt a welded joint is anything less than multiply stronger than the tie-wired joints. YMMV.
JP
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Jay Pique wrote:

I agree. Unless of course it were what amounts to a driveway (light-duty occasional use) with a mat of #8 rebar 2 inches above the bottom of the slab and a mat of #5 rebar 4 inches above that--did I mention a 15-inch overall thickness of the slab? As you can see, this is slightly overengineered. Interstate highway specs on a (literally) paved Border Patrol truck path.

I also agree there. I think the point of the statement was that the actual weld weakens the reinforcing rod at the joint because the heat hardens the steel and makes it brittle (?). I'm not sure of the (twisted) logic behind that statement.
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On 12 Dec 2004 07:35:28 -0800, snipped-for-privacy@yahoo.com wrote:

Sounds like a footer for The Wall that we're going to build.

You're right. He's wrong. Dontcha love it!
JP
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I'm not going to let that stop me. ;-)

I don't see how OSHA would be involved, and I doubt there is an ANSI standard either. There may be an ACI (American Concrete Instutite) standard, or the DOT may have their own standard.

I consulted my wife who about a million years ago as a civil engineering student did a summer internship with Illinois DOT inspecting road construction. Her recollection is that they did not tie every rebar intersection together. After compacting the road bed, the chairs are put into place and the rebar is laid down over that. She agrees that the only point to tying the rebar together is to keep them in place while the concrete is poured. So, tying every single intersection together would be overkill. Here in the North, the rebar is epoxy-coated, so welding would kinda screw that up. But where your buddy is, there may not be a requirement for epoxy-coated steel due to the lack of salt applied to the roads.
todd
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Todd Fatheree wrote:

you know, UL or ANSI or something. That gives me a topic for a new Google search. Thanks.

Thanks, Todd. You (or your lovely wife) couldn't point me toward a chapter and verse description in this regard, could you? My buddy is new to construction but old to the Army, so would like to be able to say, "Well, sir, Section 7 Paragraph 3 of the Uniform Building Code says..."
Also, this information is for his (and mine) own personal edification. Thanks again.
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I'm sorry, we can't. My wife's road-building career ended 15 years ago after her internship with IDOT and she has exclusively built high-rises and other commercial buildings since. I guess measuring concrete slump, checking asphalt truck weight, and testing concrete cylinders had a limited appeal. Although she did learn how to make "grader chicken". You wrap a raw chicken up real good with aluminum foil and place it in the engine compartment of the nearest road grader first thing in the morning. When lunch time arrives, bon appetit. Sadly, we don't have access to a road grader, so I've never been able to test the recipe.
todd
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snipped-for-privacy@yahoo.com wrote:

The California DOT has their manuals on-line. See:
http://www.dot.ca.gov/manuals.htm
-- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply)
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That should be a pretty good resource. Given the engineering requirements for assuring earthquake survivability, the specifications listed by the CA DOT will probably be as stringent as one can find. The only other possibly more stringent requirement would be for construction in areas of heavy clay.
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On Sun, 12 Dec 2004 18:30:21 -0700, Mark & Juanita

There are plenty of BOTH in LoCal. My lot was a red clay pit with half an inch of topsoil tossed on.
--
REBOOT AMERICA!
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And mine is black & grey clay. But I've built the topsoil up quite a bit. There's lots of 'byproducts' from this hobby composting behind the shed.
Patriarch
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On 11 Dec 2004 21:20:47 -0800, snipped-for-privacy@yahoo.com wrote:
... snip

... our tax dollars at work.

That particular statement alone should have been enough for the crew to have told the CWO to go pound sand. The strength of weld joints is actually stronger the the steel itself. Take two plates, weld them together, place in a vise near the seam, bend back and forth -- the steel will fracture away from the joint before the joint fractures (for a good weld job).
.. more snip

Can't help with UBC, but you might check some of the DOT web sites, I will bet that the specifications and requirements, in more detail than you would ever care to know, for interstate highway construction are available on one of their sites.

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On Sun, 12 Dec 2004 18:27:33 -0700, Mark & Juanita
|On 11 Dec 2004 21:20:47 -0800, snipped-for-privacy@yahoo.com wrote: | |... snip |>Background: |>A friend of mine is working for the Army who is doing a construction |>project for the Border Patrol in southern California. This project |>mainly involves building box culverts, runoff slabs and road beds. |>According to my buddy, these structures are built to interstate highway |>specifications, even though a 5/4 ton pickup is the heaviest vehicle |>these roads will probably ever see. They ought to be building a 50' high wall from San Ysidro to Brownsville. |> | |... our tax dollars at work. | |>The Plot Thickens: |>A Chief Warrant Officer (a surveyor by trade) told this crew, who was |>putting in a steel rebar mat, that only every third joint be tied |>together. This raised some discussion among members of the crew, one |>of which swore that OSHA required that every joint be tied. This, to |>me, sounds like a dumb-ass thing to say. ANSI maybe, but not OSHA. |>Further, he swore that the joints could not be welded, as the welding |>process weakens the steel. The Navy ought to know. | | That particular statement alone should have been enough for the crew to |have told the CWO to go pound sand. The strength of weld joints is |actually stronger the the steel itself.
Oh, please.
The discussion concerns REBAR, not steel plate. ANSI/AWS D1.4 is one applicable standard. It is quite expensive to buy.
I am not a welder, structural engineer or metallurgist, however, I've worked with all three and know that welding rebar is not a trivial exercise.
One reference I have at hand, "Placing Reinforcing Bars", Concrete Reinforcing Steel Institute, Chicago IL, 1970, states in part," The field welding of crossing bars should be avoided.... Tests have shown that this can reduce the strength of a bar to 35 to 40 percent of its capacity."
For example, one of my metallurgist co-workers investigated the results of some missile warhead testing against steel-reinforced concrete bunker targets.
The Navy built the bunkers to be used for warhead proof of performance. When the destruction exceeded the calculated results, it was determined that instead of tying the rebar in a one-foot grid; the Navy had welded the joints.
My friend showed me a one foot length of #10 rebar that looked like the ends had been cut on a shear. The whole target area was covered in one-foot long pieces of rebar and the sand that you wanted that CWO to pound.
You tax dollars funded a retest at about $1M per missile.
Thank you very much.
Here's a quick reference from a PE:
http://www.k1ttt.net/technote/welding.html
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I'm under the impression that rebar is basically cast. Welding to either cast steel or cast iron is relatively complex (gotta be pre-heated & cooled at the correct rate, etc)...not like pointing your wire welder at a piece of rolled plate or bar stock.
John
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This project

Only an engineer can authorize the use of weldable rebar and the weld specifications. It is very common to weld this type of rebar. Welding any other kind can weaken the bar ajacent to the welds, but even non-weldable rebar can be welded in certian circumstances.

From above link. The ACI 318-99 Building Code Requirements for Structural Concrete (which is referenced by all building codes in the US) states:
"7.5.4 -- Welding of crossing bars shall not be permitted for assembly of reinforcement unless authorized by the engineer." "R 7.5.4 -- 'Tack' welding (welding crossing bars) can seriously weaken a bar at the point welded by creating a metallurgical notch effect. This operation can be performed safely only when the material welded and welding operations are under continuous competent control, as in the manufacture of welded wire fabric."
Dave
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Welding and cutting torches are super no-nos on reinforcing steel. There are some cad-welding specialty end fasteners.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net
wrote:

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Actually the CWO is correct, on both comments.
Tie wire is only there to hold the rebar in place until the concrete is placed. RC is not space shuttle work or brain surgery. Just get the correct number of bars at the correct depth & you'll be fine.
Rebar is not to be welded unless it is a weldable grade. Most commonly used rebar has too much carbon. If site welding of rebar cages made sense (cost or performance) they'd be doing instead of using tie wire
cheers Bob
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On 20 Dec 2004 07:46:33 GMT, snipped-for-privacy@aol.com (Bob K 207) wrote:

Yep, following the links provided by another poster, it appears that rebar is actually weakened by welding. My bad. [slinking back to the corner for now]
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