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Force constraints on natural frequency analysis

Force constraints on natural frequency analysis

I've made a simple support structure on which about 150kg load is applied and the structure is attached to other frames.

I did natural frequency analysis (modal analysis) on the structure itself for constrained condition with displacement constraints to the frames.

I was asked whether I included the force (150kg) on the structure for the analysis.

I thought any external load would not be considered for natural frequency analysis.  Anyway, I ran the same analysis with the load on top and I got the exactly same result.

Did I do something wrong?  Or external load wouldn't matter for the analysis.

Also I see gravity load on the tap.  What would be the effect on the analysis by applying gravity load?

Thank you in advance!

3 REPLIES 3

Re: Force constraints on natural frequency analysis

example / modal prestress

regards

paul

Re: Force constraints on natural frequency analysis

Thank you, Paul!

I should've used prestress modal analysis...

One more question.  When do you need gravity load on the analysis?

Thank you again!

Seong

Re: Force constraints on natural frequency analysis

big effect by prestress: pretension is applied to ropes

and gravity load is transversely

example

regards

paul