huangyhg

pile rebar extension
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
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can't weld unless the rebar is specifically specified as weldable rebar. i can't re
i agree with broekie. the weldable rebar is astm a706. i have used the zap screwlock mechanical splice.
how will you know if you have a706 rebar? well, for one thing, you'll see a "w" in the bar mark.
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
would be possible to simply chip down th pile further and expose additional rebar? the cap / slab could be haunched down at this point.
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
while astm a706(low alloy) is more weldable than a615 (billet steel), is there some code that prevents welding of billet steel bars?
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.
...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.

you should check the carbon equivalent of the a615 rebar and see if there is a welding procedure that exists.

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