Rebar Detailing
Rebar Detailing
(OP)
I am on a job in NYC so all rebar bending is done on site.
I have a rebar detailer who detailed a bar with two bends. The drawing shows a 31'-08" bar. The delivery ticket shows a 31'-08" bar but the actual length is 31'-5.75". The bar tag says 31'-5.75" as well. He is telling me that the fabrication yard accounted for the "creep" when bars are bent and trimmed them accordingly.
Has anyone ever heard of this? I thought the bars were cut as detailed.
Thank you.
I have a rebar detailer who detailed a bar with two bends. The drawing shows a 31'-08" bar. The delivery ticket shows a 31'-08" bar but the actual length is 31'-5.75". The bar tag says 31'-5.75" as well. He is telling me that the fabrication yard accounted for the "creep" when bars are bent and trimmed them accordingly.
Has anyone ever heard of this? I thought the bars were cut as detailed.
Thank you.






RE: Rebar Detailing
RE: Rebar Detailing
Dik
RE: Rebar Detailing
RE: Rebar Detailing
I think you'll be OK.
RE: Rebar Detailing
As to the detailed length versus the delivered length, I'm not sure why they would ship a bar which was different from the length specified, plus or minus the tolerance. It would not be unusual for bars to be cut at the minimum allowed length (contract length minus tolerance.)
As for the allowable tolerances, the finished overall length of the bar is +/- 1" and the finished length of the bent ends (for 90 degree ends) is +/- 1", for #3 through #11 bars, The tolerances on #14 is +/- 2-1/2", and for #18 the tolerance is +/- 3-1/2".
If you are inspecting rebar, you should have a copy of appropriate publications handy.
CRSI/ACI 315 is being revised to make clear how/where to measure dimensions and tolerances (generally out-to-out.) The bending tolerances reported in ACI 117 and expected in the design provisions of 318 originate in committee 315 (joint ACI/CRSI committee.)
The bend radius is as specified in CRSI and ACI, and should never be smaller than the code permits. Tighter bends risk cracking and inadequate continuity of the bar through the bend radius, as well as encouraging crushing of the concrete on the inside of the bend.
RE: Rebar Detailing
Bar Shape 17, #8 Bar, 2 x 90 degrees standard bends, internal radius of bend = 3 x diam. of bar
B = D = 16 x diam = 16 x 1" = 1' - 4" , C = 29' - 0".
Reduction @ 90 bend, measured along the center line of the bar = 2.5 x diam (curvature effect. You can calculate this mathematically)
Theoretical cutting length of the bar = B + C + D - 2(2.5 x diam)
= 1' - 4" + 29' - 0" + 1' - 4" - 2(2.5 x 1") = (31' - 8") - (5") = 31' - 3".
Tolerances apart, you would get correct covers etc. only if the bar is cut to length 31' - 3" and not 31' - 8".