do i need to stagger both on plan and elevation rebar splice for a long slab on grade? 1

[delagina]

I have a slab on grade that is 70' long and will need rebar splice.
I rebar top and bottom.
I do put stagger on splice rebar location on plan view but should I stagger also top and bottom rebar?

if I have to stagger only one, which is better to stagger on plan or on elevation?

 

[delagina]

this is what i meant.. are rebar splice staggered both on plan and elevation if you have top and bottom rebars?

 

[KootK]

I'll be curious to hear what others have to say but I'm not sure that I'd be worried about either type of stagger except, perhaps, to keep them away from planned control joints. For the duties that rebar performs in typical slabs on grade, I don't feel that the stakes are high enough to warrant concern. Without any staggering, you'd probably be inviting a crack at the discontinuity but, unless you're trying to go crackless, I'm not sure that's a problem. What's the application?

As for picking one stagger over the other, I guess that I'd vote for keeping the staggers shown in plan. For shrinkage cracking, the top layer is most critical. For any flexural stresses, you'd only be working one layer of bars at a time anyhow.

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.

 

[TehMightyEngineer]

For top & bottom staggers I prefer to stack them in one location. Reason being that this typically results in more typical rebar lengths/layouts and much less chance for errors for the guys out in the shop.

About the only issue I might have with stacking them in one location is this obviously piles up twice as much rebar in one location. If my thickness or bar center-to-center spacing is small, then I might get a slight congestion issue at the location of all the lap splices.

Regarding cracking I'm actually wondering if doubling up the splices might not be beneficial. While you might not have the best tensile capacity you have twice as many dowels crossing the crack as the areas without lap splices. Seems like that would count for something.

Otherwise, as KootK pointed out, it shouldn't make any difference structurally whether you stagger then or not as you're highly unlikely to have both taking tension in a slab (or beam).

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

http://www.americanconcrete.com

 

[dik]

what you are proposing doesn't hurt, but sawcutting at the correct time is critical. If sawcut at the right time, doesn't matter if you stagger splices.

Edit: Sorry, didn't mean to imply that you can stagger splices and forget about sawcutting at the right time.

Dik

 

[SlideRuleEra]

It is recommended that staggered splices are only used when they are essential to the design of a structure due to the complexity they add to both the detailing and placement of the reinforcement.

The complete document, "CRSI Engineering Technical Note ETN-D-2-13, Staggered Lap Splices" is attached.

Suggest avoiding the proposed splice detail circled in red on the marked up illustration shown below.

1. Rebar placement does not require that level of precision.

2. Fabrication of that detail is an unnecessary expense.

3. In the field, the proposed rebar has to be turned one way for the splice pattern to work. Straight bars work in either direction.

4. If any field changes in rebar length are required (it happens), shortening (cutting) has to be done on the correct end. If longer bars are required... what do you do? Have more bars with the special end detail delivered? With straight bars, field changes are easy (may have to add an extra splice location, or two... not a big deal).

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[dik]

Thanks SRE... didn't consider that he could be using 'cranked' bars.

Dik

 

[SlideRuleEra]

You are welcome, dik, always nice to keep things as simple as possible.

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[TehMightyEngineer]

I assumed he wasn't using cranked bars and was just showing that the bars were intended to be lap spliced at that location. At least that's how I've always interpreted that bar detail.

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

http://www.americanconcrete.com

 

[dik]

...didn't know for sure; now it's clear.

Dik