ACI 318 Definition of "Slender Walls"

[JoshPlumSE]

I was recently going through the design code provisions for slender walls and I'm confused by some things that I'm seeing in ACI 318.

1) ACI 318-2008 section 14.8 never actually gives a definition of a "slender wall". Any ideas why this is, or am I missing something.

2) The old definition from the UBC days was whenever the H/t ratio was greater than 30. I think this went through a few slight modifications over the years. But, it was always pretty close to the classic h/t > 30 ratio.

3) ACI section 14.6 now has a section which says that "non-bearing walls" cannot have an H/t ratio greater than 30. Again, ACI fails to define what a non-bearing wall is.

If I'm following the new ACI code, can I still use my old trusted slender wall procedure (section 14.8) for walls with an H/t ratio greater than 30. Or, does section 14.6 prevent me from doing so?!

I was hoping that the IBC 2009 would have some additions or modifications to this section of the code to clear up these problems.... but, no such luck.

Can anyone else give me some insight on this subject?

 

[JAE]

Does the definition matter for any logical sequence in the code? It seems that 14.8.1 states that you must be tension controlled.

 

[msquared48]

Josh:

I would still use PCA Slender Wall Design, limiting the H/t to 50 as bewfore. None of mine have failed.

As for a bearing wall, neglecting the self weight of the wall itself, it is a wall where the joists and/or rafters are not parallel to the line of the wall.


Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[JoshPlumSE]

Apparently, it has always been like this.... all the way back to the 1997 UBC.

It's the Masonry code that really required the slender wall procedure whenever H/t > 30. That makes sense because my slender wall design has almost always been based on masonry (at least up until this point). I don't see a similar requirement in ACI anywhere.

Regardless, it still strikes me as odd that masonry allows walls with an h/t ratio greater than 30, but that ACI doesn't seem to (based on section 14.6). Am I still missing something?

 

[ash060]

You can always design a wall in accordance with Chapter 10 and use those provisions for slenderness effects, than there is no limiting slenderness ratio