Uplift check-Precast concrete shear wall with effective flange width

[Sandychan]

Hello everyone,
I am doing a design of a precast concrete shear wall. It is a one-story wall taking a horizontal force. Checking this wall alone, there is an uplift. I try to connect this wall with some walls perpendicular to it to gain some counter weight. As a result, the shear wall has a T-shape which the perpendicular walls form a flange with an effective flange width. The width of the flange is equal to effective flange width suggested by ACI 318. In my case, extending the flange by the wall height/4 from each side of the web governs. I used all gravity loads within that effective width to help prevent the uplift. Unfortunately that is still not enough.

I am wondering if we can more length of perpendicular walls to help against the uplift. Attached are a sketch of my design situation. Thank you so much in advance.
Best regards,
Sandy

 

[KootK]

I am wondering if we can more length of perpendicular walls to help against the uplift.

Absolutely. The ACI provisions that you mentioned are really about the effective load spread in taller, monolithic, cast in place walls. In my opinion, not all of that applies to a precast wall setup. I would absolutely consider those provisions, in some form, if you were using flanges in compression, which you're not.

If you post a sketch showing the panel joint layout of your "flange" wall, I can probably provide more detailed advice. Basically, you can claim as much flanged wall as you like so long as:

1) You design the flange wall and connections for the loads and;

2) You don't create a situation wherein local connections are over-stressed by the activation of the load path that you assume for #1. Basic deformation compatibility.

In most cases, I'd expect you to be able to claim somewhere between one and two full panel widths as resisting dead load for the shear wall under consideration.

 

[Sandychan]

Hi Kootk,
Thank you so much for your quick answer.
Attached are elevation of the walls that will form a flange and a sketch of how the web and the flange should connect.
After wall No. 4, there still may walls standing in a row.
If I can use full weight of wall No. 2 and 3, it should be enough to resist uplift in my case.

Anyway, let's assume that wall No. 7 located really far away and weight from wall No. 2 and 3 are still not enough for uplift, does it mean I can use the weight of more walls to help with uplift as long as I can satisfy the 2 conditions you mentioned above.

Thank you again.

 

[KootK]

If I can use full weight of wall No. 2 and 3, it should be enough to resist uplift in my case.

I think that you can use 1/2 of the weight of panel two and 1/2 of the weight of panel three before you start getting into exotic connection requirements between panels.

does it mean I can use the weight of more walls to help with uplift as long as I can satisfy the 2 conditions you mentioned above.

Yes but you'll have a hard time with my condition #2 if your go beyond panels two and three.

 

[Sandychan]

Thank you so much for your explanation, KootK. It is very clear to my question. I believe I got the answer I need to finish my assigment.