Issues with modal analysis

[Rafael_Oliveira22]

Hello,

I found some problems with my modal analysis on RSA.

I know it is a old problem and have so many posts about it on forum, but I couldn't solve my problem.

Firstly, I haven't found any value for mass rotation (Rz) in the modal analysis for my building, so, after searching for a solution on Forum, I found that mass rotation "Rz" is only available for analysis with "Slab - Rigid Diaphragm".

(the same problem of him https://forums.autodesk.com/t5/robot-structural-analysis-forum/robot-modal-analysis-torsional-mass-p...)

So, after using the API Diaphragmer from @Romanich (Thanks for your help with the API, Roman), I still haven't values for mass rotation (Rz) in my building. I tried to change the options for mass matrix in the modal analysis (Consistent or lumped) and I did a simple model for test this options with the API Diaphragmer and I got good values for Rz in this model for example but, when I try to use the same options for my building, I can't found values for Rz in modal analysis.

Someone have any idea how can I solve this problem for mass rotation (Rz)?

I have spent so many time to solve it and I could not.

I will attach my models and auxiliar pictures for discrib the problem and results.

Thanks!

@Romanich 
@mustafahesenow 

@Artur.Kosakowski 

@Pawel.Pulak 

@Rafacascudo 

@Rafal.Gaweda 

@teixeiranh 

[Rafael_Oliveira22]

Anyone?

[Rafael_Oliveira22]

Can you help-me, @Krzysztof_Wasik?
Any idea how can I solve it?
Thank you!

[Rafacascudo]

Maybe @okapawal  can help you on this one

[okapawal]

I had a look at the model.  It is a couple story, wide and long building.   Maybe just torsional vibration form is not dominating like in the test model in mode 3.

Why do you need RZ mass participation result?

[Rafael_Oliveira22]

Thanks for your attention, @Rafacascudo 

Thanks for your reply, @okapawal 
So, I started to compare the values for dynamic analysis with almost like structure on ETABS and when i did compare the values for Rz I thought it was a little weird, because I think we always have any mass rotation for a building, however small it may be.

When we see the Model 1 for the Main model, we can observe that building is susceptible to torsional vibration on the first mode but without Rz.

Finally, i Would classify my building according NP EN1998-1 (5.2.2) like Torsionally flexible system.

[Simau]

@Rafael_Oliveira22 

To return to your simple model, could you test these 4 models with ETABS

[Rafael_Oliveira22]

@Simau 

I will attach the result for modal analysis for the 4 models you asked.

I hope I haven't forgotten any data for the models.

I made a simplified report with some pictures, If any question, tell me.

Thank you