topic Re: Modal analysis taking into account static forces in Robot Structural Analysis Forum

Modal analysis taking into account static forces

Ludwigswe — Mon, 07 Nov 2016 10:24:30 GMT

Hello!

I wonder why I get the same frequency for two different load magnitude?

Case 1 the uniformly distributed load on the bridge is 0,3 kPa and for Case 2 1,0 kPa

Case 1 No. 1 Egentyngd taking account No. 3 Beläggning(0,3kPa).

Case 2 No. 18 EgenviktFall2 taking account No. 19 Fall2(1,0kPa).

It is mod 10 that I examine. 5,14Hz

Should be less for Case 2!

See link

https://www.dropbox.com/s/penbo199n6uq92p/ModalAnalysHela.rtd?dl=0

Regards

Ludwig

Re: Modal analysis taking into account static forces

Artur.Kosakowski — Mon, 07 Nov 2016 10:47:16 GMT

Unless you consider these loads as masses I'd expect the effect to be visible only when the applied load causes large tension forces in a structure.

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Re: Modal analysis taking into account static forces

Ludwigswe — Tue, 08 Nov 2016 04:57:42 GMT

I thought that the static load, that i choose too account for, always transforms to masses and that the masses are placed in the area of the structure where the load is assigned!?

I don't understand the formulas in the Help part!

Are both stage carried out each time a "Modal analysist taking into account static forces" runs?

Stage one does not include mass matrix?

Can you please tell me more about how this analys type is working!

Re: Modal analysis taking into account static forces

Artur.Kosakowski — Tue, 08 Nov 2016 08:24:14 GMT

I thought that the static load, that i choose too account for, always transforms to masses and that the masses are placed in the area of the structure where the load is assigned!?

No, it is not. You have to convert it into mass. The main objective of this analysis type is to consider the stress level which may be due to pulling the element (a guitar string analogy).

Can you please tell me more about how this analys type is working!

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

Re: Modal analysis taking into account static forces

Ludwigswe — Wed, 09 Nov 2016 13:48:34 GMT

Now I got it!

Dziekuje barza

Re: Modal analysis taking into account static forces

Artur.Kosakowski — Wed, 09 Nov 2016 14:10:34 GMT