CMU Vertical bar spacing vs dowel spacing
CMU Vertical bar spacing vs dowel spacing
(OP)
On the vast majority of load bearing CMU wall design we do in our office, the vertical bar spacing is established and all vertical bars are extend to the foundation via dowels. In other words, the vert bar spacing matches the dowel spacing. I am wondering if anyone has experience with only providing dowels at 50% of the verticals? In my particular case, I'm looking at specifying wall verticals at 24" o.c. and dowels at 48" o.c. Technically, the wall is fine with bars spaced at 48" all around, but would there be any benefit to providing additional bars that do not extend to the footing?






RE: CMU Vertical bar spacing vs dowel spacing
RE: CMU Vertical bar spacing vs dowel spacing
RE: CMU Vertical bar spacing vs dowel spacing
RE: CMU Vertical bar spacing vs dowel spacing
RE: CMU Vertical bar spacing vs dowel spacing
RE: CMU Vertical bar spacing vs dowel spacing
By doubling the reinforcement you are doubling the lateral strength, since each filled cell is only carrying half the load. I seriously doubt the controlling factor in this wall or any other reinforced CMU wall is the connection to the foundation. I would guess in most instances friction and the bond strength of the mortar would calc out to meet your in- and out-of-plane shear requirements. Throw in your bars at 48" o.c. and you are WAY over designed for those two loading conditions. In my experience in high wind conditions, net uplift at the foundation can be a concern for shorter walls (less dead weight), and then the capacity of the bond beams since they span between the filled cells and have an uplift force applied to them.
All of these things in my experience end up normally being cursory checks of your standard calcs and details, the real issue is lateral and axial combined loading of the CMU itself.
HTH,
a2k
RE: CMU Vertical bar spacing vs dowel spacing
Mike McCann
MMC Engineering