Staggered or Non-Staggered Rebar Laps? 1

[waytsh]

Working on a construction plan for a large grade beam/strip footing and debating how to locate the longitudinal bar laps. The way it is working out with the rebar lengths available if I stagger the laps some of the laps will be in the high moment region under the columns. If I use non-staggered laps I can keep them in the lower moment region, roughly half of the maximum. I am leaning towards using non-staggered laps. The bars are number 8 and they are spaced at over 9" so congestion should not be a problem. Thoughts?

 

[JAE]

Non-staggered requires Class B laps for sure.
Staggered may or may not require Class B and allow Class A.
That would be a consideration - the additional 18" +/- lap lengths required.

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

 

[waytsh]

Thanks for the quick reply JAE. Laps will be class B. They will actually be several inches in excess of a Class B splice due to the material the contractor has in stock. We are not going to bother to cut off the extra few inches. Out of curiosity, do you have a reference for the non-staggered laps required to be Class B? Thanks.

 

[JAE]

ACI 318-11, Table R12.15.2 summarizes section 12.15.2. All non-staggered laps must be Class B.


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

 

[TehMightyEngineer]

As a small aside, I generally use staggered splices where it's easy to do regardless of whether it gets me a class A lap; it is a stronger setup that's not as discontinuous.

We had a contract truck driver roll his trailer over and dump a large precast arch onto the shoulder (no casualties thankfully). The piece split right at the non-staggered splice location when it hit. Obviously this was a gross overload of the arch but I'm reasonably confident it wouldn't have split that badly (or at all) if I had a staggered splice there. The piece split from what I guessed was a flexural-torsional failure so nothing against class B laps for normal loads.

Incidentally, don't take a sharp corner at speed when you're hauling a 25 ton, top-heavy arch.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/