Modal Analysis Mass

[aendersilva29]

The STAAD give me the values of frequency similar to robot, but the rel.mas.Ux, dont pass the 90%, if i take the frequency of the mode that pass the 90%, its bigger of the STAAD

[Stephane.kapetanovic]

hi @aendersilva29 

just to understand, could you give us the values calculated by STAAD and their exact name?

Best Regards

[aendersilva29]

Frequency X: 1.27

Frequency y: 1.49

I attach the model of Robot

[Stephane.kapetanovic]

hi @aendersilva29 

you've already given your Robot model in the other topic about design parameters (lateral buckling).
I can't compare two calculations if I don't have the values.
However, I notice that you've only taken live loads into account as masses.

Best Regards

[aendersilva29]

I only take the overloads as masses because i dont check disregard desity, what I understand is that self-weight is automatically considered mass.

About the STAAD calculations you need the file? or what you need to can compare?

[Stephane.kapetanovic]

hi @aendersilva29 

see private message
i don't think that 2 seconds for a non-braced articulated structure is a surprising result.

i'd even say that the results can be even different if you consider the relative stiffness of the joints.

Best Regards

[Simau]

Hi @aendersilva29 

You didn't reply to my question in message 2 of this topic

https://forums.autodesk.com/t5/robot-structural-analysis-forum/ratios-are-incorrect/td-p/12731193

[Stephane.kapetanovic]

hi @aendersilva29 

it seems that the values are the same

RAYLEIGH FREQUENCY FOR LOADING 22 = 0.49517 CPS

Best Regards