ACI 318-19 Special shear wall Design with non uniform shape

[dstruct99]

How would you approach the design of a special reinforced shear wall (as per ACI 318-19) with a non-uniform shape such as this? See the attached file.
Where would the boundary elements be? What would be your critical section? What height would you use for calculating the h/l ratio?

 

[lexpatrie]

If you need boundary elements, they'd likely be at the ends of the individual walls, then you have to develop anchorage into the wall below as needed to appropriately terminate it.

h/L ratio would likely change for each floor.

Think of it as a multistory wood shear wall if that helps, there's a hold-down at each end of the top wall and the panel has to deal with the shear induced by the transfer force in the lower, longer panel, from the (modeled) point load at the end of the shorter upper wall. Draw some free-body diagrams if it helps, neglecting any vertical forces that aren't at the ends.

 

[dstruct99]

Thanks, Lexpatrie for your input.
If I put boundary elements in each segment of the wall, then the entire wall will be covered with boundary elements only. As you can see in the sketch, each segment is only 3 ft in length. The wall is 18 inches in thickness. Not sure if this would be a problem. I need to look into that.
Your analogy regarding the wood shear wall makes sense.
But, unlike the wood shear wall, do you think there should be a boundary element at the top of the wall, that is sloped (connecting points E, C, B, and A)?

 

[lexpatrie]

This seems like relatively little wall, I took the drawing as a three story building. Can just the 3' wide x 6' tall portion work by itself? The dimensions of this thing are fairly unusual.

 

[dstruct99]

Yes, this is a fairly unusual shape for a shear wall.
Think of this as a single-story wall supporting 3-flight stairs with intermediate landings at 3 levels. For the out-of-plane seismic forces, the intermediate landings should be able to brace the wall. My inquiry is for in-plane forces.

No, the 3' x 6' wall segment does not work by itself. I need the full length of the wall. Note that the supports are only at the ends (not a continuous support at the base).