I do not have the most recent version of ACI 530, but in Section 8.5.7.1.1, it says 0.002 times the bar diameter times the allowable stress in the reinforcing. With Grade 60 reinforcing, this works out to be 48 bar diameters. DaveAtkins
Thanks a 10^6- In the 1999 version, the new section is 2.1.8.6.1.1. There is a handy-dandy ref. chart referring 95 version sections to appropriate 99 sections (it is in the back of the 99 version).
ACI 530 stipulates 48 bar diameter. Also a side note that most engineers do not know, a splice of bars can be in two adjacent cells (YES) per ACI 530!!!! They do not have to be in the same cell. It is preferred but not necessary.
Not sure if you are also working under the IBC but it overrides ACI's laps for working stress design (IBC-2000 2107.2.3) and can control the final legnth.
48 bar diameters. I also can give you a little known fact that most engineers do not know or are aware of, ACI 530 allows the vertical bars, when splicing, to be in adjacent cells. They do not have to be in same cell!!
I always call out an extra 3" to 6" inches of lap, depending on the height of the wall, between the dowels coming out of the footing and wall reinforcment. The reason I do this is, depending on how sloppy the mason is, there can be a significant amount of mortar that falls down the cells prior to grouting the wall.
This is one of the reasons you have clean outs at the bottom of the walls/lifts. Before the cells are filled, you can inspect them. Also you can inspect them after the grout is placed to confirm solid core grouting.
MMOT is correct. The lap lengths under the IBC can be much greater. For example, a #6 bar in 8" cmu would be approximately 65" instead of the 36" required by ACI 530-99. Does anyone know the rationale behind this? Has this been a failure mode? I doubt it. Based on earlier responses in this thread, are other engineers sticking with ACI and ignoring the IBC requirements?
