shear wall dimension section ratio

[h-badawy]

Dear all

is there any section in ACI mentioned the min. ratio between the width and the length of the shear wall otherwise will be designed as a column ,
With the knowledge that there are some of codes limited with this ratio like BSI.

 

[ahmedhegazi]

i have not seen any limitation in ACI 318 , whatever the way you model / reinforce it , you have to satisfy strength and buckling requirements.

the number i use is length/thickness < 4 (Model as frame ) otherwise model as shell

 

[KootK]

I also use four as my limit although I can supply no reference to back it up. I also no of no explicit limit in ACI. Small world. Can you tell us what some of the other codes, like BSI, have to say about this?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Guest262653]

From Eurocode 2 - EN1992-1-1, 5.3.1(7):
"A column is a member for which the section depth does not exceed 4 times its width and the height is at least 3 times the section depth. Otherwise it should be considered as a wall."

Guess we're all in the same page.

 

[MrHershey]

I see 4 used a lot. I'm not aware of any limitations from a gravity or low seismic standpoint, but there's certainly guidelines for high seismic.

ACI 318-11 updated to include some provisions on 'wall piers' for special walls that had actually been in the IBC concrete chapters (and ASCE 7 concrete chapters) for a while, since at least 2003. Looks like IBC 2012 actually takes out the new section from ACI 318-11 and replaces with the same modifications that have been in place for several code cycles now.

In any event, 'wall pier' is defined as have a cross-sectional aspect ratio less than or equal to 6 with a clear height to horizontal length aspect ratio of at least 2. If you're under a horizontal aspect ratio of 2.5, 21.9.8 actually kicks you into designing the 'wall pier' as a column in a special moment frame including *all* of the fun hoop spacing and size requirements. If you're between 2.5 and 6, 21.9.8 gives you some simpler options. IBC goes one further than ACI 318-11 and actually puts the wall piers requirements in the special moment frame area as well, implies to me that the provisions would apply for standalone elements as well as portions of larger walls.

So would seem that by an aspect ratio of 6 you should at least start thinking of some of the column provisions. And by an aspect ratio of 2.5 you should be following all of them. At least from a high seismic standpoint. Direct from IBC modifications to chapter 21 special moment frame and special wall sections: 'wall segments with a horizontal length-to-thickness ratio less than 2.5 shall be designed as columns'.