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Lap Splices vs. Bundled Bars regarding Concrete Cover

Lap Splices vs. Bundled Bars regarding Concrete Cover

Lap Splices vs. Bundled Bars regarding Concrete Cover

(OP)
ACI 318-11, Section 7.7.4 states "For bundled bars, minimum specified concrete cover shall not be less than the equivalent diameter of the bundle, but need not be greater than 2". While Lap Splices do not equate to Bundled Bars, do they need to be considered when determining concrete cover?

For example, a #8 bar with a 1" cover is fine, but is it still fine if a lap splice is required placing two #8 bars side by side?

RE: Lap Splices vs. Bundled Bars regarding Concrete Cover

By my understanding; yes there is no change in clear cover.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: Lap Splices vs. Bundled Bars regarding Concrete Cover

This has never occurred to me. I can't supply an explicit reference to back up my opinion but I agree with TME: no change in clear cover at laps.

Rationally, I'll back my opinion up like this:

1) A bundle of bars means more tension than one lone bar would produce.

2) More tension means more demand for force development.

3) More demand force development means more demand for cover as the cover is part of the concrete doing the developing.

4) Lapped bars do not introduce additional tension and, therefore, require neither additional development capacity nor additional cover.

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: Lap Splices vs. Bundled Bars regarding Concrete Cover

(OP)
Thanks, that makes sense from a design standpoint. I was wondering if it had more to do with the placement of the concrete. More steel means more obstacles for the coarse aggregate, so a thicker cover may help the aggregate flow around the outside of the bars. Picture a row of 4' vertical dowels splicing with the vertical bars in a wall. In theory, properly sized aggregate and proper consolidation by the contractor should work fine, but I wanted to make sure this wasn't a factor to be considered.

RE: Lap Splices vs. Bundled Bars regarding Concrete Cover

Well, remember that you still have the minimum clear spacing between bars in the lap splice for exactly the reason of consolidation and coarse aggregate.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: Lap Splices vs. Bundled Bars regarding Concrete Cover

(OP)
Agreed. Thanks.

RE: Lap Splices vs. Bundled Bars regarding Concrete Cover

Different cover conditions are part of the detailed lap splice length determinations, so cover is already accounted for in the design of lap splices.

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