Reinforced Masonry Question

[jheidt2543]

In reviewing a set of plans, I ran across this question. The structural engineer had a table that gave the required lap length for reinforcing rods grouted in the cores of the block. At some locations, next to vertical control joints, he calls out #6 rebar with an 8'-2" lap. Why so long? I thought 40 bar diameters was pretty much standard.

Of course, the poor mason that has to do this will have to figure out a real trick. Lifting a 8" or 12" block over the top of the lap bar is no small task. Yes, there are special connectors that can be used, but I just don't see why an 8'-2" lap.

Any enligtening comments?

 

[LPPE]

Here's a worthless one - Maybe the 8 was supposed to be a 3?

 

[JAE]

Based on the new ASCE 530-02, a #6 bar in a cell, with 2000 psi grout, would require a 52" lap. If you put TWO #6 bars in the same cell, that lap would grow to 112". Perhaps the engineer confused one bar with two.

 

[MMOT]

We have also run into this situation with long laps in walls where there are 2 bars- to help with the constructability problem, I detail the wall using "conduit blocks" (open end units) which have one open end so that the block does not have to be lifted over the bar. This is detailed in the military TM 5-809-3 which can be downloaded at

http://www.usace.army.mil/inet/usace-docs/armytm/

I'm just glad to be reassured by JAE that I was correct in my calculations/interpretations- I've had to prove it several times over and I still don't think the Architect and Contractor believe me...