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# Moment curvature in weak axis

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## Moment curvature in weak axis

(OP)
Can anyone please tell me when it comes to moment curvature analysis why do we focus on the strong axis of the walls only? Don’t we need to examine the displacement capability of the wall in weak direction more? I understand that the moment in weak axis can be ignore but the point of moment curvature analysis is to check the member’s displacement capacity and since the wall connects to the diaphragm that will drift in both direction, why don’t we check the moment curvature of wall in weak axis (out of plane) direction?

### RE: Moment curvature in weak axis

It's a good question that I have wondered about myself. I built a 20'-0" long, 1'-0" thick wall with #5 at 12"oc, to aid in discussion.

Below is the moment rotation curves that I get with 0 axial load on the wall:

Strong Axis

Weak Axis

I want to build a model to confirm, but my guess is that typical loading/wall arrangements will never be able to develop 200kip*ft of moment in the out of plane direction (appears to be approximate onset of rebar yielding from the graph). I would guess that the wall just lacks enough stiffness to develop that much moment.

S&T

### RE: Moment curvature in weak axis

(OP)
Thank you. Do u mind tell me what software u used to generate these moment curvature?

### RE: Moment curvature in weak axis

Software is called "Sketchulation", really cool software that has way more power than I know how to use currently. Kinda a mathcad/cross section analysis tool/general all purpose analysis program if you know how to use it.

Definitely the easiest arbitrary concrete cross section analysis tool I have used.

S&T

### RE: Moment curvature in weak axis

(OP)
Thank you.I will have a look.

### RE: Moment curvature in weak axis

Not sure if I understand correctly. But, walls are very strong against bending in one direction and very weak on the other, if you have a building that has several walls spanning in both orthogonal direction (say X and Y axis) then loads coming from one direction, say x-axis, will be mainly resisted by walls having its strong axis at x-axis (due to force distribution by stiffness). Force coming from x-axis going to walls having a strong y-axis will be negligible.

### RE: Moment curvature in weak axis

I just tried to search for Sketchulation but can only find a few videos and links to trademark registries. Is it still out there somewhere?

### RE: Moment curvature in weak axis

Definitely still out there, but you are right it is not the easiest thing to google and find great info.
Youtube channel is here:

https://www.youtube.com/watch?v=tndIrt-UN9c&t=...

I will reach out to the creator of the software to see if he won't pop his head into this thread.

S&T

### RE: Moment curvature in weak axis

From the creator:

#### Quote (Mike K.)

Anyone can try Sketchulation for free. Go to www.tippingapplications.com to register and request a trial license. It's free for students (need to have access to a valid edu email address) and for one month for everyone else.

S&T

### RE: Moment curvature in weak axis

Thanks. Requiring people to register just so they can enter the website and read about the product seems a little silly....

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