Verification of modal analysis Results
Why If I solve one small model (concrete building 10 floors) by using Etabs and the same building By Using robot I see the different results for modal analysis from each program
If the basics and concepts are the same in each one of them then why we get different results.
I hope any one can answer my question
Re: Verification of modal analysis Results
Please post more details about structure model and some details about the input and output from modal analysis.
Re: Verification of modal analysis Results
Quote:
Originally Posted by
medo
Please post more details about structure model and some details about the input and output from modal analysis.
thanks for your helping
But did you model any building by robot and Etabs and compare dynamic analysis result?
I will try to post the model
once again I have to thank you for your post and assistance
1 Attachment(s)
Re: Verification of modal analysis Results
My model etabs v9.7.1 and RSA2011 sp2
results are same. ıts perfect run.
no problem modal analysis. bye
falconado
Re: Verification of modal analysis Results
Quote:
Originally Posted by
troy_the.best
My model etabs v9.7.1 and RSA2011 sp2
results are same. ıts perfect run.
no problem modal analysis. bye
falconado
I found one thing
Sometimes when I use Riigid diaphragm With Salb (Flexible Rigid Diaphragm XY) I got this problem , I do not know why
I think rigid diaphragm some times creats a problem with dynamic analysis
Re: Verification of modal analysis Results
Yes you are right. when use rigid diaphram or semi rigid diaph. its given wrong results. İ hope from autodesk this bugs is fix on next Sp3 patch. Good works.
Re: Verification of modal analysis Results
Quote:
Originally Posted by
troy_the.best
Yes you are right. when use rigid diaphram or semi rigid diaph. its given wrong results. İ hope from autodesk this bugs is fix on next Sp3 patch. Good works.
Robot with a lot of Bugs!!!
See, when I try to use Seismic Loads by Using UBC code
and applied the value of base Shear say Vx = 1000 KN,
I found that robot does not multiply the results with a scale factor to be matched with the new values
For example :
Static seismic load say = 1000 KN
Dynamic seismic load say = 500 KN
now robot should Multiply the Seismic dynamic load by factor = 1000/500 =2
this as per UBC because dynamic loads should not be less than static load
But Robot did not do that, and this is also one more Bug there.
Thank you
1 Attachment(s)
Re: Verification of modal analysis Results
mechiel,
look this jpg UBC scale factor in robot. have a nice days.
falconado_turkey
Re: Verification of modal analysis Results
Quote:
Originally Posted by
troy_the.best
mechiel,
look this jpg UBC scale factor in robot. have a nice days.
falconado_turkey
Hi falconado,
thank you for your helping,
But this is not hte scale factor,
this is the direction of ritz vector
when we apply the seismic in X direction we put X=1
when we apply seismic in y dir we put Y=1
After that we use a respondse spectrum curve UBC
then program we calculate the seismic forces in X and Y
then we will get Vx= 1000 say (Dynamic) ; and Vx = 500 (Static) say
so all results of dyanimc seismic should be multiply by scale factor =0.5 = Vstatic/Vdyn
Regards
Re: Verification of modal analysis Results
Mech
Maybe it can help you
When u use directional X=2 it means that you have doubled seismic force in that direction