Design of Shear Reinforcement for a Concrete Wall 1

[oengineer]

I am working on designing a wall to resist excessive shear. In order to keep from increasing the thickness of the wall, I am trying to find information on the Design of Shear Reinforcement for a Concrete Wall.

Is their any technical design info regarding the designing of Shear Reinforcement (i.e. stirrups) for a Concrete Wall?

Suggestions/comments are appreciated.

 

[driftLimiter]

There are many different technical guides for this. Not sure where you are practicing but this is a good reference for ACI 318. [URL unfurl="true"]https://www.nehrp.gov/pdf/nistgcr11-917-11.pdf[/url]

There are maximum limits that you need to watch out especially if your using a shear controlled wall. Could also explore higher grades of reinf. to keep it from getting to congested.

 

[oengineer]

There are many different technical guides for this. Not sure where you are practicing but this is a good reference for ACI 318.

https://www.nehrp.gov/pdf/nistgcr11-917-11.pdf

There are maximum limits that you need to watch out especially if your using a shear controlled wall. Could also explore higher grades of reinf. to keep it from getting to congested.

Thank you for the document! Do you happen to have any information which shows a design example of Shear Reinforcement for a Concrete Wall?

 

[driftLimiter]

I can recommend the 2018 IBC SEAOC Structural/Seismic Design Manual Volume 3 - Examples for Concrete Buildings

 

[le99]

I suggest reading these two articles, one for euro code, and one for ACI, to gain insight into shear wall design.

https://www.structuralguide.com/shear-walls/

https://structville.com/2020/11/design-of-shear-walls.html

 

[JedClampett]

I've reinforced walls for shear, but my conclusion is it would have been better to thicken the wall. More concrete in a wall is a marginal cost, as the formwork, reinforcing, etc. is already paid for. I've had concrete subcontractors tell me that they'd prefer a wall thicker than about 24 inches, because they can send the rodbusters in between the mats to tie the bars. Plus the wall will behave more ductile, with a smaller reinforcing ratio.
If you're close, maybe a stronger concrete (5000 psi?) would help.

 

[Celt83]

unlike some of the others I assume your are talking about out-of plane shear strength of a wall not in-plane.

For out-of plane shear first take advantage of the more advanced shear equations that include the contribution of axial force. If you still need shear reinf. increase the wall F'c, if that doesn't work make the wall thicker. Stirrups in walls for out-of plane shear will lead to a lot of congestion in the wall so typically avoid them.

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[SRO]

I'm designing a concrete shear wall and I'm a little rusty so poking around on line for a "refresher" I came across a very helpful YouTube channel from Tyler Ley. He's big a professor from OSU that is very involved w/ ACI.

Here is the shear wall video.

https://www.youtube.com/watch?v=PyVR0Or_YyE

 

[oengineer]

unlike some of the others I assume your are talking about out-of plane shear strength of a wall not in-plane.

Yes, I am talking about out-of-plane bending of the wall. The wall is 26 ft tall and shall be retaining soil underground.

I have been asked to see how I can get away with using a 24" thick wall that is 26 ft tall to retain soil.

 

[driftLimiter]

What about stepping the wall thickness near the bottom, Moment and shear are accumulating rapidly as you approach the bottom, like Celt suggests, Shear reinf for out of plane is rather unwieldy. Its a tall wall dude, I don't think its surprising that your 24" Thick segment is running out of gas.

 

[JedClampett]

A 26 foot tall wall should be close. Suggestions:
[ul]
[li]Support it at the top.[/li]
[li]Provide a drainage system (with an alarm).[/li]
[li]Use lightweight fill (or cellular concrete).[/li]
[/ul]

 

[JLNJ]

I punched a few quick numbers and the magnitude doesn't seem all that crazy. It seems like a minimal amount of stirrups would work without too terribly much congestion. And the force tapers off pretty quick so no stirrups once you are above 6' or so.

I'm not sure how the shear force gets out of the wall and into the footing. Maybe a full-width key?

 

[WinelandV]

I've done the wall design on a wastewater type facility once, and I do a fair amount of boot pits and transfer tunnels for grain receiving.

Generally, the "correct" answer is to just make the wall thicker. This may involve a slightly larger hole for excavating as you'll need to have a larger footing.

Even if you can r/f it with stirrups, as JLNJ then noticed, you still have to get the shear into the footing. Shear keys are rife with issues, so you'll be looking at reinforcement using shear friction to get the shear into the footing. This can lead to some rather large diameters and/or tight spacing of your dowels.

So, not impossible, but it can be a LOT of extra work - tying those ties is going to be a chore. On the cost side, speaking with a local contractor, he was telling me that in the last year rebar went from $600/ton to $1600/ton. So the old adage of "steel is cheap (in concrete)" may not hold up as well.

If it must be 24", then you should look at the options that JedClampett has proposed.

Please note that is a "v" (as in Violin) not a "y".

 

[le99]

One suggestion is to place embedded beams to cut short the segment span length (say @8' oc) and to count on the columns to support the reactions at the beam ends.