re_bar couplers use in R.C.C
re_bar couplers use in R.C.C
(OP)
WE ARE PLANNING TO USE REINFORCMENT BAR COUPLERS FOR IMPORANT RCC STRUCTURES, FOR CONNECTING BEEMS AND COLUMNS . THE COULPERS ARE PLACED JUST ON FACE OF COULEMN JOINING BEEM REINFORMENT.
IS THERE ANY LIMITATION IN USING REBAR COULPERS WHICH ARE THREADED TYPE LIKE BARTEC COUPLERS, FOR BEEMS AND COLUMNS?.
WHAT IS CODE POSITION IN USE OF THESE COUPLERS FOR CRITICLE STRUCTURES?.
ANY EXPERIENCE AND OBSERVATIONS ARE WELCOME
IS THERE ANY LIMITATION IN USING REBAR COULPERS WHICH ARE THREADED TYPE LIKE BARTEC COUPLERS, FOR BEEMS AND COLUMNS?.
WHAT IS CODE POSITION IN USE OF THESE COUPLERS FOR CRITICLE STRUCTURES?.
ANY EXPERIENCE AND OBSERVATIONS ARE WELCOME





RE: re_bar couplers use in R.C.C
RE: re_bar couplers use in R.C.C
I remain musing if, where it feasible, placing them at the center of the joints themselves wouldn’t be better. Main gain would be a complete concrete entourage, sides, top and bottom.
In any case, and in whichever the position you place the welded rebar connectors, I recommend to use stirrups in such disposition and as close as to ensure such confinement that the gain of concrete strength for confined concrete is standing. This may mean placing stirrups thicker than usual and at 3 to 5 diameters separation there. Extend such stirrup reinforcement for say a total height of thrice the height of the connectors.
Another practice one might consider is not to make 100% of the connections at the same station. This however may be unconstructive and against the understanding of that being the connection mechanically ensured, such precaution becomes unnecessary.
RE: re_bar couplers use in R.C.C
RE: re_bar couplers use in R.C.C
RE: re_bar couplers use in R.C.C
A good bar coupler should certainly not have and noticable slack when properly installed. Maybe you have a problem there.
In any case, it is preferable to avoid bar couplers if possible in any location where stress reversals in the bar are likely, particularly under dynamic loading or in earthquake-critical zones. Even a good correctly installed thread-type coupler could develop slack due to thread deformation or bedding-in under stress reversals.
RE: re_bar couplers use in R.C.C
A Linton Threaded coupler is the only threaded coupler that does not have any "slack" in the threads because the threads are tappered ... similar to iron pipe threads. Any non-tappered threads will have some slack as a result of the tolerances required to thread a female and a male thread together.
I've performed seismic researsh using reinforcing couplers. If you're in a seismic zone, a coupler that develops 150% of yield is required (Linton threads won't develop 150% of yield), but the codes make no comment on the "slack" often inherent with threaded couplers.
Two things that won't have any slack:
1) Crimped on couplers. I found these to be the best for areas of high seismic risk.
2) Applying epoxy to the threads of standard couplers. They must be upset threads (fatten the rebar and then cut the threads to keep from decreasing the Xsectional area of the rebar by cutting the threads directly into the rebar.
Hope this helps.
RE: re_bar couplers use in R.C.C
RE: re_bar couplers use in R.C.C
RE: re_bar couplers use in R.C.C
I have seen the Linton (or is it Lenton?) coupler and it is a very good no-slack design provided it is properly installed. I would only recommend for bars where the extension piece is straight, to avoid the chance of a rebar worker only screwing the bars together up to the point where a bent end points in the correct direction.
And, as you say, because the threads are cut into the rebar, it will be almost, but not quite as strong as the original bar.
I do not know of any research into the notch effect of the threads under long-term cyclic loading, such as on a highway bridge. The mechanical engineers may have some guidance here, based on the sharpness at the bottom of the thread root.
Crimped-on couplers are good if you can get the machine into the space. There was a brand called Camtak / CCl if I remember correctly, but I do not know who does it now.
pdprao,
I do not know the details of your structure or the Bartec product or the design codes in your area, but it does sound as though you should investigate the slack problem further, and perhaps ask your supplier to produce some design information and perhaps certification.
PXC,
It was BryanStein who suggested the epoxy.
I agree with what you calculated on the epoxy stresses, and doubt that epoxy would work reliably. Epoxy strengths vary depending on the formulation, and the epoxy is in a confined compression area, but even so, I would hesitate to expect it to carry more than about 150 MPa.
The contact stresses between threads can be somewhat higher than the tensile strength of the bar, hence the 'bedding-in' effect. Therefore, for example, cylinder head bolts are re-torqued after running a piston engine.
RE: re_bar couplers use in R.C.C
I have now found some product information on the Bartec coupler at www.ancon.co.uk.
It can be tightened to the extent that it will be free of slack, but they do not recommend the use of a torque wrench for this model.
I would consider it to be slack free for static loads or for dynamic loads that are always in the same direction (always tension or always compression in the bar).
I would not consider it suitable for dynamic loads where there is stress reversal (sometimes compression and sometimes tension in the bar).
RE: re_bar couplers use in R.C.C
I have used all these types of couplers in seismic research projects. The crimped on is the best, and I have used epoxy in the threads of upset thread couplers with great success ... yes, I know the epoxy is overstressed when the numbers are checked.
RE: re_bar couplers use in R.C.C
RE: re_bar couplers use in R.C.C