topic Re: Seismic force plot and results verification in Robot Structural Analysis Forum

Seismic force plot and results verification

antonio.lafuente — Thu, 21 Oct 2021 09:51:21 GMT

Good morning

I am a bit suspicious of my seismic analysis results and was wondering whether I may have missed something. To start with for some reason I can't manage to plot the seismic loads the code is generating even after running the analysis and having checked the right option under preferences.

Second, if I look at the reactions from the seismic load cases the values look pretty low for the close to 100 Ton of converted mass taken into account in the modal analysis and the response spectrum I'm using.

Am I missing something? There seems to be something off with these results. I'm attaching anyway the file in case someone can have a quick look and give me a hand. Thanks a lot in advance

Re: Seismic force plot and results verification

Romanich — Thu, 21 Oct 2021 10:27:20 GMT

Hi @antonio.lafuente ,

What I can see on Robot 2022, that you have execution error 2550 related to the eigenvalue problem (internal error while reading from a scratch file during eigenproblem analysis)

Re: Seismic force plot and results verification

antonio.lafuente — Thu, 21 Oct 2021 11:52:00 GMT

Strange. I don't have such error with Autodesk Robot 2020

Re: Seismic force plot and results verification

Simau — Thu, 21 Oct 2021 11:59:54 GMT

Hi@antonio.lafuente

Change the order of the load cases in order to have the seismic cases directly after the modal case.

Re: Seismic force plot and results verification

antonio.lafuente — Thu, 21 Oct 2021 12:22:48 GMT

Hi!

That seems to have helped :). Thanks! I still can plot the forces though. Any idea on how to do this?

Re: Seismic force plot and results verification

Romanich — Thu, 21 Oct 2021 13:34:06 GMT

Re: Seismic force plot and results verification

antonio.lafuente — Thu, 21 Oct 2021 14:18:41 GMT

Thanks! Is this the only way? Can you not plot it in the load definition section? I though I had done this in the past or seen it done elsewhere

Re: Seismic force plot and results verification

Romanich — Thu, 21 Oct 2021 16:23:02 GMT

Hi @antonio.lafuente ,

In addition it is possible plot as added masses converted from the load:

Or check results in the table:

Re: Seismic force plot and results verification

antonio.lafuente — Fri, 22 Oct 2021 06:21:45 GMT

Thanks! Bu t shouldn't I be able to see these forces when activating forces generated automatically?

Re: Seismic force plot and results verification

antonio.lafuente — Fri, 22 Oct 2021 09:44:13 GMT

Hi again Simau

I'm going through the results and maybe I'm missing a concept from the theory side, but shouldn't the spectrum applied on the X direction result in reactions only in the X direction? It is for the same model I attached in the beginning

Cheers

Antonio

Re: Seismic force plot and results verification

Simau — Fri, 22 Oct 2021 10:33:37 GMT

@antonio.lafuente

nothing abnormal since your structure is not perfectly symmetrical in load and rigidity