POSITION OF RE-BAR COUPLERS - ACI CODES
POSITION OF RE-BAR COUPLERS - ACI CODES
(OP)
Hi
POSITION OF RE-BAR COUPLERS - ACI CODES
I am using re-bar couplers in continuous beams. I am trying to find justification for where they are positioned in the
ACI codes but without success. I have tried 318, 315, 439.
The general concensus is that they should be staggered; top couplers between 1/4 and 3/4 of the span; bottom couplers in the first and last quarter of the span; concrete construction joints, where unavoidable, at about 1/3 of the span.
Is there any justification for this in the codes
Please advise
peakpilgrim
POSITION OF RE-BAR COUPLERS - ACI CODES
I am using re-bar couplers in continuous beams. I am trying to find justification for where they are positioned in the
ACI codes but without success. I have tried 318, 315, 439.
The general concensus is that they should be staggered; top couplers between 1/4 and 3/4 of the span; bottom couplers in the first and last quarter of the span; concrete construction joints, where unavoidable, at about 1/3 of the span.
Is there any justification for this in the codes
Please advise
peakpilgrim





RE: POSITION OF RE-BAR COUPLERS - ACI CODES
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
Why do you say that a mechanical splice is a lap splice? I disagree.
There should be no technical reason to restrict the location of couplers if the full bar strength is developed. The only issue I know of is reduction of cover at the splice, as the coupler is larger than the bar. And then there is quality of installing the couplers, which is probably a good enough reason to place them other that at maximum force positions.
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
1) A lap splice joins two discontinuous bars. Ditto for a mech splice.
2) A lap splice could be designed for full strength. Ditto for mech splice.
3) A lap splice is considered less reliable than no splice. Ditto for mech splice.
In my mind, we choose to locate lap splices so as to minimize the ratio of demand to reliable capacity. I don't see why this same logic wouldn't inform our choices when it comes to locating mech splices.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
lapsplice is still alapsplice. I simply meant to imply that similar principles ought to inform the placement of all kinds of splices. Clearly, a lap splice is a mech splice no more than a cat is a dog.I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
There are a few code clauses, like the tension tie business, that create the impression that mechanical splices are more reliable than lap splices. I think it's misleading and a consequence of one -- or both -- of two things:
1) Usually these are situations where members aren't really being treated as true, composite, reinforced concrete. Rather, they are just steel tension members that happen to be encased in some durability enhancing concrete.
2) As a profession, I sense that we don't really trust our rank and file to properly detail these critical, zero redundancy disturbed regions. And, sadly, I agree with that position.
I think that this comes down to one question that I shall put to you. Do you believe that a mechanical splice is as reliable as continuous bar that has not been spliced in any way? My field guys have brought me two of these gadgets now that have seemingly spontaneously combusted during install. So You can guess how I feel about it.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
I'm actually going to withhold the identities of the coupler manufacturers. I don't want to be slandering them based on a couple of isolated experiences. I will say that it was neither Ancon nor Reidbar.
Some interesting, related ACI clauses:
24.5.7.3 Mechanical splices do not need to be staggered
24.5.7.3 Commentary. Staggering of mech splices is encouraged and may be necessary due to congestion. A little vague.
25.5.7.4 Tension tie splices should be staggered at least 30"
Take from that what you will.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
No requirement to stagger mechanical splices except as required for congestion or for in tension ties
318-14 Chapter 18 has requirements for seismic cases, particularly in special seismic frames and walls.
Tension splices are tested under ASTM A1034 to 1.25*fy in most cases. Because of this, while most designers keep them away from critical sections, they can theoretically be located anywhere along the length of a bar. There are no restrictions on where mechanical splices can be located in non-seismic members.
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
Maybe you can just tell me the type of coupler which failed. I don't like the tapered ones.
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
Don't get me wrong, I like mechanical couplers and use them often. I just don't thin that their infallible.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: POSITION OF RE-BAR COUPLERS - ACI CODES
Kootk, I thought you were using a thermite splice.
RE: POSITION OF RE-BAR COUPLERS - ACI CODES