Maximum rebar spacing in CMU wall 2

[FSS]

My understanding is that some, but not all, codes limit the maximum spacing of vertical rebar in CMU walls to 48". ACI 530 has limits on the effective width to be used for compressive stress (least of bar spacing, 6 times wall thick, or 72"), but nothing with regards to flexural design. Can anyone direct me to applicable sections where rebar spacing limits are discussed?

 

[CAOranger]

It is the minimum of 48", L/2 and H/2 per UBC 2106.1.12.4. It also has minimum percentages based on the gross section.

 

[CTSeng]

Strictly using allowable stress design there are no limits on the maximum spacing of vertical rebar only the effective width for compressive stress as stated. I've found some local codes that restrict the spacing to 72" or 96" but this is as far as I would go as a practical limit. It's always cheapest to push the spacing as far a possible because it's fewer cores to grout and it often results in less overall steel required as well.

Take a look at the download "Test Report-Effective Width "b"" avaible from Masonry Institute of America at:

http://www.masonryinstitute.org/index.php?ACTION=LQPR

It's an oldy but a goody. There are several other good downloads from this site as well.

Ultimate strength design does, however, have some reinforcement limits that may restrict bar spacing.