Lapping of reinforcing bars with different spacings
Lapping of reinforcing bars with different spacings
(OP)
Hi All,
I understand it is good practice and will make fixing of reinforcing a great deal simpler on site, but is it really required (from any code point of view) to maintain spacing of reinforcing over a change in moment?
i.e. In a wall to wall corner I require 16mm bars horizontally @ 150 spacing (on the outside face). Still on the outside face but moving away from the corner I can comfortably change the spacing to 200 centers. There is a sharp drop in the moment. Is it ok to do this?
Thanks.
I understand it is good practice and will make fixing of reinforcing a great deal simpler on site, but is it really required (from any code point of view) to maintain spacing of reinforcing over a change in moment?
i.e. In a wall to wall corner I require 16mm bars horizontally @ 150 spacing (on the outside face). Still on the outside face but moving away from the corner I can comfortably change the spacing to 200 centers. There is a sharp drop in the moment. Is it ok to do this?
Thanks.
_________________
Jones & Wagener
www.jaws.co.za






RE: Lapping of reinforcing bars with different spacings
RE: Lapping of reinforcing bars with different spacings
In practice,I never detailed it like that.
RE: Lapping of reinforcing bars with different spacings
1) Remain in compliance with your code's max spacing for non-contact lap splicing.
2) Treat the unconventional lapping as a strut and tie problem and supply suitable vertical rebar to make that work.
3) Use an extended lap length if your code has provisions for that. I believe it is NZ that allows you to space your bars further apart if you add 1.5X the space to the length of the lap.
I detail with #3 and verify with #2 sometimes.
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: Lapping of reinforcing bars with different spacings
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: Lapping of reinforcing bars with different spacings
In my experience, this has been a problem when developing tension from a superstructure element into a drilled pier. The anchor rods are in the center of the pier while the pier reinforcement is around the exterior which could be 12"+ away. To justify the correct embedment length, I would assume a concrete cone failure for the embedded anchors and then make sure I had the drilled pier reinforcement developed by the time it intersected with the plane of failure. Appropriate ties prevent the splitting that happened in the ACI case study.
In your case, Unless you have perpendicular reinforcement to the outside, I'd be concerned with the reinforcement bursting the face of the wall and losing development.
RE: Lapping of reinforcing bars with different spacings
So long as the reinforcing remains within a single plain, as I believe the case to be here, there should be no cross wall bursting tendency to deal with.
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: Lapping of reinforcing bars with different spacings
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Professional and Structural Engineer (ME, NH)
American Concrete Industries
www.americanconcrete.com