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sag04 (Structural) (OP)
1 Dec 05 10:15

Due to the miscalculation of cutoff level, now I’m facing the 60 cm length shortage of pile rebars in to pile cap. How can I extend the rebars? By welding or splicing? What is minimum welding length required for 20mm dia torsteel in this condition?
Thanks
Regards
broekie (Structural)
1 Dec 05 11:04
Can't weld unless the rebar is specifically specified as weldable rebar.  I can't remember the ASTM number for weldable rebar, maybe A708.

I would probably use some kind of a mechanical splice.  Without knowing more details about he geometry, maybe cut the existing bars 1' or so above the top of the pile.  Then use a mechanical splice and a new piece of rebar to get the correct length.

Hope this helps.
bjb (Structural)
1 Dec 05 11:09
I agree with broekie. The weldable rebar is ASTM A706.  I have used the Zap Screwlock mechanical splice.
crossframe (Structural)
1 Dec 05 13:25
How will you know if you have A706 rebar?  Well, for one thing, you'll see a "W" in the bar mark.


lutein (Structural)
2 Dec 05 18:08
you normally dont have A706 unless you specifically called them out in your Contract Docs.  Check w/ your contractor.
Also - You might want to look into using Dayton's BarLock mech. splice system, because it does not require pre-thread rebars.
Hope this helps
DRC1 (Civil/Environmental)
4 Dec 05 9:54
Would be possible to simply chip down th pile further and expose additional rebar? the cap / slab could be haunched down at this point.
Dinosaur (Structural)
5 Dec 05 13:33
As previously stated, you should only allow ASTM A706 reinforcement to be welded (not ASTM A615 reinforcement) and A706 bars will have a "W" on the bar mark below the bar size.

If I understand the problem properly, I would expect a mechanical bar splice to be the cost effective method of obtaining the required bar length.  A lap splice will require an extra three feet of bar or something like that.

You may need to check if ties/spirals would be required if you want to use a lap splice in this situation.

Dinosaur
henri2 (Materials)
6 Dec 05 4:20
While ASTM A706(low alloy) is more weldable than A615 (billet steel), is there some code that prevents welding of billet steel bars?
Dinosaur (Structural)
6 Dec 05 10:43
The PCI Design Handbook, Chapter 6, mentiones this.  It says while the AWS D1.4 Welding Spec for Rebar states most steel may be welded, D1.4 has preheat and other requirements for high carbon steel.  Because of this High Carbon Equivalent portion, it is recommended that A706 be used because it is unlikely A615 will meet this.
henri2 (Materials)
6 Dec 05 11:27
...and PCI's Manual for QC for Plants and Production of Structural Precast Concrete Products MNL 116 on page 3.7 says something similar "The weldability of reinforcing bars other than ASTM A706/A706M shall be evaluated according to the provisions of AWS D1.4"

Well what does D1.4 say? My edition (98) allows welding of A615 bars with CE over 0.75 (Sec 1.3.1 item 7 and Table 5.2). For billet steel bars where the CE is unknown, D1.4 Sec 1.3.4.3 stipulates min preheat requirements based on bars sizes; 300 deg F for No.6 and smaller and 500 deg F for No.7 and larger.

I guess many agencies are not as liberal as AWS and only allow welding of low alloy bars unless special approval is granted for welding other rebar (i.e approval of WPS by dept). Even in the case of welding low alloy bars in lap and butt splices, some agencies still require departmental approval.

 
apetr26542 (Structural)
16 Dec 05 15:37
You should check the carbon equivalent of the A615 rebar and see if there is a welding procedure that exists.

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