Execution Problem 902

[Anonymous]

Hello all

I am trying to model a simple bridge for seismic analysis using pushover method. I guess modal analysis is an essential part of the process but when I set the analysis mode to seismic (in modal analysis parameter) I get an error 902. I tried to pin the bearings and fix Rx but it did not work. However when I set the above option to just modal it works. I would appreciate if someone can help me out. the model is attached.

Kind Regards

[Refaat · Accepted solution]

Hi @pooria_panahi

1. Shell module should be used instead of Frame 3D module.
2. I think the reason behind display the error (Execution Problem NO: 902) is that the negative eigenvalue has been obtained in the mass matrix. Therefore I suggest you to use the matrix type “ lumped with rotations’’ instead of “ lumped without   rotations’’ and for more precise results” consistent “ might be used .
3. Disregard density option must be activated since you include the self-weight in the converted mass.

Refaat

[Anonymous]

Thanks man, it worked well. but do I have to change the structure type to shell and analyze again or the results are now reliable ? I still don't understand why I get unrealistic deflection in the mid-span under just dead load !?!?

I would appreciate if you could also tell me how to define nonlinear hinges for beams/columns and see their formation and limitation, generate demand curve for pushover analysis ?

Best Regards

[Refaat · Accepted solution]

Hi @pooria_panahi

Do I have to change the structure type to shell and analyze again or the results are now reliable?

Yes, you need to reanalysis your structure inside shell module since you have panels.

I would appreciate if you could also tell me how to define nonlinear hinges for beams/columns and see their formation and limitation, generate demand curve for pushover analysis?

Please, take a look to these useful links.

https://knowledge.autodesk.com/support/robot-structural-analysis-products/learn-explore/caas/CloudHe...

https://knowledge.autodesk.com/support/robot-structural-analysis-products/learn-explore/caas/CloudHe...

Refaat

[giovanilombardi]

I was losing my mind trying to solve this problem. Thanks a lot!