Notes on Welding Re-Bar
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
1997 UBC (Uniform Building Code) -- used mainly west of
"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
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.
Concrete (which is referenced by all building codes in
"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