Deflection check and limits of free standing cantilever wall exposure to wind 2

[ak.t]

Dear All,

Could any body explain the Deflection check considerations and limits for free standing cantilever wall exposure to wind?

Thank you,

 

[phamENG]

Need more info. What's your wall made of? What is the wall doing? How tall is it? Where are you and what is your local building code? The answer is going to be different if you have a 4' wood wall blocking the view of a generator in a field vs. an 11' brick wall along a busy sidewalk.

 

[ak.t]

Dear phamENG, It is 4m in length and 3.4m high precast self standing boundary wall subjected to 1.10 kN/m2 wind pressure. Footing provided is 1.7x1.35m which is eccentric. We use ACI standards.

 

[r13]

I don't think there is a rigid limit on the deflection of free standing pre-cast concrete, or concrete, walls. However, you should focus on ensuring there is no easily detectable deflection of the wall (non-slender), and no permanent deflection resulted from failure of the subgrade (excessive bearing stress). Both are quite subjective, and require engineering judgement. IMO, the best is to follow successful examples of the past projects, and keep the bearing stress low (compared to the allowable bearing pressure).

 

[ak.t]

Oh, retired13, u changed ur id name to r13.

Reviewer wants sway analysis for this. So, I'm trying to get some inputs/ reference.

 

[Celt83]

The reviewer likely wants you verify that P-Delta effects were considered so when the wind blows and initiates some deflection that any loads on the panel+sw don't generate enough P-Delta effects to destabilize the system.

The ACI has a section on alternate design of slender walls that has some limits on the deflections along with the modified design moment.


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https://github.com/open-struct-engineer

 

[r13]

Yes, I've shortened my user name

The plan reviewer could be looking for the inclusion of column slenderness designation and effect of sway mechanism considerations (ACI 318-14 Section 6.6). A rare request for boundary wall design. Suggest to contact the reviewer for guidance; I suspect he sees something that is considered unusual, or something he dislikes.

 

[ak.t]

Thank you all for your valubale inputs. will look into it and if I have questions regarding this (procedure, calculations), will ask you again. Thanks a lott for your time and response.

 

[klaus.]

P_Delta effect on a 3.4 m high free concrete standing wall ??
Is there any load ob top of the Wall that could cause Stability problems ??

 

[ak.t]

Dear klaus,

This is the exact situation. Length of the wall is 4.0 m

 

[r13]

Why shrink the footing? Did you perform stability analysis?

 

[ak.t]

No retired13. I did not. I considered the central portion as column

 

[r13]

Okay, seems you were not treating this as retaining wall, but as a free standing column. Then, there are at least two factors, other than stability, that the reviewer does not like it:

1) Excessive slenderness ratio (too flexible). (See the linked article, Link)
2) Seemly lacking required flexural strength. (If only reinforced with single layer of steel or wire mesh).

Please discuss the design with a senior engineer.

 

[canwesteng]

Maybe there are some other considerations at play here, but I don't think that shape is really saving you much money if any when you account for all the forming you'll need to do.