Reinforcing Bar Lap Length Question

[marinaman]

I have a question regarding lap lengths of reinforcing bars.

If we have a concrete wall (say 10" thick), and we have #5 bars at 10" o.c., each face, horizontally for temperature and shrinkage reinforcing, what is the required lap length?

I've got shop drawings to check on such a wall.......

He's lapping the bars by 30 bar diameters......which would be 19"

But these are in tension......so if I followed ACI 318, a tension splice would be 40" in this instance.

But I don't need the full Fy.....its just temp and shrinkage reinforcing.

Can I accept the 19"? Could I accept the 19" if the laps are staggered from each other? Seems like there should be a provision for something like this.

 

[KootK]

I believe that temperature and shrinkage bars do, in fact, need to be developed and spliced for fy.

 

[DaveAtkins]

I think ACI would say you DO need the full fy for temperature and shrinkage control.

That being said, I wouldn't ask for longer lap lengths. I think a 30 bar diameter lap splice was traditionally used in the past, with no problems that I know of.

If the bars were acting as tension reinforcement in a structural member, I would ask for the full Class B lap splice.

DaveAtkins

 

[Celt83]

(say 10" thick), and we have #5 bars at 10" o.c., each face, horizontally for temperature and shrinkage reinforcing,

I'd take another look at this as #5 @ 10" each face sounds pretty heavy for just temperature and shrinkage.

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[BridgeSmith]

I thought AASHTO and ACI were fairly similar for required laps and temperature & shrinkage reinforcement. Under AASHTO, for a 10" thick wall, S&T would be the minimum value of .11 sq. in. per ft, so #4 at 18" would be enough. The lap for a #5 Top Bar is either 29" (old ASD/LFD spec) or 31" (new LRFD spec).

Rod Smith, P.E., The artist formerly known as HotRod10

 

[LearningAlways]

Fy is definitely required, otherwise you have nothing to combat the cracking.

 

[Settingsun]

I'd take another look at this as #5 @ 10" each face sounds pretty heavy for just temperature and shrinkage

Maybe it's actually restrained. Those low quantities (<0.2%) are significantly weaker than the concrete so the stress that causes cracking mostly has to dissipate such as at contraction joints, rather than being picked up by the reo.

I agree that 30*diameter will probably do this job. Depends on concrete strength and cover etc though.