ACI 318-08 Section 14.8.2.6
ACI 318-08 Section 14.8.2.6
(OP)
Can anyone shed some light on the requirement, "Vertical stress Pu/Ag at the midheight section shall not exceed 0.06f'c"? This seems extremely restrictive. For 4000psi concrete, this value is 240psi. This is something I might expect to see in masonry, but not concrete. Your thoughts on this provision are appreciated.





RE: ACI 318-08 Section 14.8.2.6
RE: ACI 318-08 Section 14.8.2.6
This goes way back to the UBC days and the slender wall testing done by SEAoC. If you really want to go back through the history of it, take a look at the 1980's publication: "Report of the Task Committee on Slender Walls". This was published by SEAoC and the Southern California Chapter of ACI.
P.S. It's one of my favorite research reports because it was commissioned by and performed by engineers.... Not academics. :)
RE: ACI 318-08 Section 14.8.2.6
My question is this, is 6% of f'c a hard number based on empirical evidence or did someone say 6% late one night and they went home for the day. I have a situation where I am trying to make a 6" (ICF) wall support hollowcore planks. My P/A at the midheight is closer to 10% of f'c. Is this completely out of bounds? Do I have to design by Chapter 10?
Thanks for all your input, past and future.
RE: ACI 318-08 Section 14.8.2.6
I think it would be best to bite the bullet here and use a thicker wall, or different product.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: ACI 318-08 Section 14.8.2.6
You do not mention retained soil or similar indication that it is a basement, so the empirical method should be acceptable. 14.4 allows design by the strength methods in chapter 10.
The alternative method is a simple method, which is why its requirements are more restrictive than necessary under chapter 10.
RE: ACI 318-08 Section 14.8.2.6
Hit the nail on the head. Agree with that.
RE: ACI 318-08 Section 14.8.2.6
RE: ACI 318-08 Section 14.8.2.6
http://www.seaoc.org/bookstore.html
Test Report on Slender Walls
"Green Book." Research report on testing of 12 concrete wall panels, nine concrete block masonry panels, and nine block panels ranging in h/t ratios between 30 and 60.
September 1982 129 pp.
Order SC #82-1 | Member $20.0 | Nonmember $25.00
Now, a quick review of what I see is that the axial load limit may reflect a limitation in what was tested. They say they really only tested the axial load up to a value of 1/10th the "short column axial capacity". That corresponds to approximately 0.06*f'c.
Hard to believe that no one else has done any significant testing on this over the years to see how the behavior changes with increase axial load. At least to see how high you can go before the procedures stop being valid. But, that is entirely possible.