Rebar Lap Splice Locations

[DCBII]

I was told I should not splice rebar in a flexural member near the point of maximum moment. I can't seem to find anything to back that up in ACI 318 though. The closest thing I found is limitations with regard to splicing integrity reinforcement in perimeter beams. Thoughts?

 

[JAE]

ACI 318-11, Section 12.10
(see also the Figure R12.10.2 below)

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[DCBII]

JAE,

That image you posted is for bar cutoffs. How does it relate to splices?

 

[TehMightyEngineer]

The two areas of concern are seismic detailing and general efficiency.

For general efficiency, you obviously should splice in the lowest loaded areas available. This is just good practice in the event of overloading or an error in design/construction. You get a credit on lap lengths required if the rebar being spliced is more than twice the area required by design.

For seismic design with intermediate or special detailing you need to keep your lap splices away from the plastic hinge regions. This means splicing in the middle of beams and columns if you're designing moment frames (contractors love this...).

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[KootK]

In short, other than high seismic requirements, the code allows you to place your splices wherever you choose. It is sound practitioner judgement, rather than code prohibition, that leads designers to generally avoid splicing at points of maximum moment. That said, if there a compelling, practical reason for splicing at high moment locations, have at 'er. Some other steps you could take to improve matters if you're going to do it and are concerned:

1) Mechanical splicing.
2) Provide longer splices than normal.
3) Provide more rebar than the minimum required for flexure.

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.

 

[KootK]

A few recent discussions on similar topics.

Link
Link
Link

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.

 

[DCBII]

KootK,

I agree with you the more I think about it. It may not be the best practice, but I don't think it's prohibited. My understanding is that small compression struts form from the ribs of one bar to the ribs of its neighbor to transfer the load. I don't see how the magnitude of the moment could change this behavior.

 

[JAE]

Sorry DCBII - I was "reading into" your post that you were dealing with bar length detailing.

Agree with KootK on "anywhere" but a continuous bar is inherently more capable than a splice in concrete - just because.

Section 7.13 deals with integrity reinforcement and throughout there are references to top bars being spliced near midspan and bottom bars spliced near supports.



Check out Eng-Tips Forum's Policies here:
faq731-376