Structural Analysis of Reinforced Concrete Wall

JohnnyB_ · May 6, 2022

I am working on designing an ICF wall 16' tall that will support a 3rd level. The elevation view is in the attachment.

My question is, when doing the structural analysis to estimate the ultimate moment should I consider it to be a cantilevered beam, fixed at bottom and free at top or a beam pinned at top and bottom?

Assuming the cantilevered beam method seems very conservative but the pinned at top and bottom seems unconservative. In reality the wall will be tied to the foundation with alternating hooks of the vertical rebar #5 @ 18" O.C. (for the sake of discussion). I assume this will carry some moment until hairline tension cracks form in the concrete, then it would act as a pinned connection. Thanks in advance!

KootK · May 6, 2022

We usually design walls like this as simple spans from bottom to top. That said, this implies that you'll have a competent, stable diaphragm behind the top of the wall and appropriate connections to that diaphragm.

jayrod12 · May 6, 2022

What is the building lateral system. a 16 foot cantilever likely won't calculate out. I'd bet you NEED a diaphragm at the top of the wall to support it. If said diaphragm exists, and there's a lateral system in place for the diaphragm to dump the load into, I see no issue with designing it as pin-pin. That's how I would do it, but whatever steel I determined I'd be putting on each face of a wall that tall.

le99 · May 6, 2022

Where is the third level? I see two. For which, if well braced against lateral sway, both the floor and roof can act as support.

dik · May 6, 2022

As Koot notes... simple span. There should be little difficulty in getting your roof and floor to provide diaphragm action for the four outer walls. About 30 years back, I had a tall ICF wall supporting roof only. I used the column design program to create an interaction diagram for axial and flexural load.

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JohnnyB_ · May 6, 2022

Thanks for the feedback.

Kootk: My upper floor and roof connection will supply a sufficient diaphragm in order to use the pin-pin calcs (attached DiaphramCnnx.PNG).

JohnnyB_ · May 6, 2022

The lateral sway of the roof is resisted by the northern and southern sheathed walls and a center beam column frame (attached LateralSway.PNG).

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Structural Analysis of Reinforced Concrete Wall

JohnnyB_

Structural

KootK

Structural

jayrod12

Structural

le99

Civil/Environmental

dik

Structural

JohnnyB_

Structural

JohnnyB_

Structural

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