pushover running but not leaving elastic region

[jefe7066]

Dear STKO Support Team,

I am working on a pushover analysis of a one bay frame with a nonlinear truss representing masonry infill. Once it didn't leave the elastic region (monitor graph was linear increasing), I tried with a single degree of freedom element with the same nonlinear material properties and got the same response. I attached both files here. The one degree of freedom one is called cantilever test and the bay is called newpush1bay. I used ex 22 from the Asdea tutorial on nonlinear analysis/W15 as reference. I ran that one just fine and can't figure out why I am not getting a similar response with my simpler models. Please let me know if you see something I don't and what I can do to fix them.

Thanks!
Jeanette

[STKO Team]

Your simple (cantilever) does enter the nonlinear range.
You just need to increase the applied load, because based on your material parameters you are not yet in a strongly nonlinear regime.
I refined your mesh to better illustrate the results. As you can see, part of the lateral displacement comes from the elastic deformability of the beam, while another part results from the nonlinear rotation of the hinge.

nnl.png (73.01 KiB) Viewed 520 times

[jefe7066]

Dear STKO team,

Thank you! What force did you use? My units are Kips and inches (sorry), and I was already using 1e15 kips, which seems like an incredibly large load for the pushover (based on the tutorial, which used a much larger 3-story structure). Could you identify which material properties were making it so hard to reach the nonlinear region? I also messed up and meant to send this with the spring in the x direction. Is that possible?

Another question, I am worried there is something wrong with the way I apply my force or my analysis steps, because in the post-processor, on the top node, I get the graph below.

I would also like to see element results to verify the nonlinear spring response by plotting the force-displacement response and checking my yield stress. Any help in that area would be greatly appreciated.

Thank you,
Jeanette

[STKO Team]

share the file to have a look

[jefe7066]

Here is the zip of the full model I am working on. I need it to run in pushover and can't tell why it's not working correctly. Please let me know if you can find what is wrong. Additionally, the equivalent diagonal strut values are quite high, even though I used multiple equations, so I am not sure why that happened either.

[STKO Team]

Try this.
The problem is that your model is very brittle, so you need to play with convergence criteria when this happens