Cross section forces

acorella

Hi.

I've searched the forums but could not find an answer to my question, even though I think it may be quite basic.

I've modeled a simple wall element (using shell elements), supported at the bottom ends & with a point load at the top in the middle, as shown below:




The results are as one would expect, with compression struts forming in between the load and the supports, as shown below.




My question is, how do you find the resultant of forces at a certain cross section cut? Ideally, this would be for the total effects from all the stresses. But I could also work with it if it was split up by the different local direction, for example below, showing stress in the UU direction.



Thanks!

Victor

1. Create a face selection for the internal faces along the section cut, which has to be aligned with element boundaries.
   
2. Solve
   
3. Add Solution -> New force and moment -> force per length
   
4. Use Solution -> Surface integral to integrate the force per length components over the face selection.
   

Here's an example where we expect the internal force to be 5 N in the U direction and 3 N in the V direction. Obtain them by integrating force per length UV and force per length V respectively.

You could probably use stress in element coordinates instead of force per length and skip a couple of steps.

acorella

Thanks, Victor!

Now I suppose there would not be an easy way to also find the resultant flexural force acting on on the netural axis of that section cut? The left side is pulling up and the right side is pushing down, so there is a resultant moment.

I'm thinking this might have to be done outside on a spreadsheet, but there might be some other clever way to do it.

Victor

I think you can do that by adding a Solution -> New formula which produces moment per length about some axis, such as

FL.vv * x

for the internal force.liml file I attached. Then integrate that in the same way to get total internal moment about Z on that surface.

Somehow that formula doesn't include the other force component, FL.uv, so I'm not really confident that it's correct and maybe needs an extra term.

acorella

Got it. Thanks.