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[TowerTalk] Foundation too close to Tower?? -- Welding of Reinforcing St

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Subject: [TowerTalk] Foundation too close to Tower?? -- Welding of Reinforcing Steel
From: (
Date: Mon, 28 Jan 2002 17:28:55 +0000

I wrote a response to your original post but I guess it 
is somewhere in the ozone....

I think a general discussion of Welding Reinforcing 
Steel is necessary. I think I have responded to this in 
the past but this should cover the full spectrum of this 

Reflectorites should be able to search on the subject 
now and get a decent answer...

The Welding of Reinforcing Steel in concrete is covered 
by the several building codes used in the United States.

1997 UBC (Uniform Building Code) -- used mainly west of 
the Mississippi.

"1903.5.2  Welding of reinforcing bars shall conform to 
approved nationally recognized standards. Type and 
location of welded splices and other required welding of 
reinforcing bars shall be indicated on the design 
drawings or in the project specifications. ASTM 
reinforcing bar specifications, except for A 706, shall 
be supplemented to require a report of material 
properties necessary to conform to requirements in UBC 
Standard 19-1."

UBC Standard 19-1

19.101.1 ".........., the welding of concrete 
reinforcing steel for splices (prestressing steel 
excepted), steel connection devices,inserts,anchors and 
anchorage details,as well as any other welding required 
in reinforced concrete construction, shall be in 
accordance with the Structural Welding Code -- 
Reinforcing Steel, ANSI/AWS D1.4-92..."

What this says that if you want to weld normal 
reinforcing steel which is normally ASTM A 615 grade, 
you need to follow the requirements of the AWS D1.4 for 
electrode specifications, min. weld size, type of weld  
and most importantly the preheat requirements... I 
believe that this is 300 degrees F for a minimum of 20 
minutes prior to welding.

If you use ASTM A 706 reinforcing bar then no preheat is 
required for welding.

However note that the intent of welding reinforcing 
steel is focused on direct splices and connections to 
other metal devices to be embedded in the concrete, not 
for rebar cage assembly or tacking in lieu of wire ties.

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."

As an aside I looked the topic up in the 1996 BOCA Code 
and the 2000 IBC(International Building Code) and they 
both refer to AWS D1.4 for welding and ASTM A 706 as a 
weldable reinforcing bar.

There you have it.. The codes do not want you to tack 
weld the tie bars in a rebar cage, but if you must use A 
706 bars and use the procedure in AWS D1.4.

Use wire ties for your cages.. I have been practicing 
structural engineering for over 30 years and have yet to 
see a problem with using wire ties for field assembly of 
reinforcing bar cages.

Concering the 5 foot set back from your house foundation 
I'm a little confused by this. A few questions are in 

What is the frost depth in your location?
What type of house foundation do you have (stem wall, 
How deep is you house foundation?
Do you have a basement?, if so, How deep is it?

With this knowledge then a case could be made to move 
the foundation closer to the house. I don't understand 
the 5' for 5' depth concern.

With respect to your question if the bid amount was 
reasonable. You do not give enough information on what 
exactly was bid and where you live and what the 
prevailing wage wage and rental rates are. I would say 
that off hand it is on the high side of typical but not 
out of reason. Better information gets a better answer.

Hope this helps you, again I don't know what happened to 
my first response. All the best


Hank Lonberg, P.E./ S.E., KR7X

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