Modal analysis taking into account static forces

Modal analysis taking into account static forces

Ludwigswe
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Modal analysis taking into account static forces

Ludwigswe
Enthusiast
Enthusiast

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).

Fall1.JPG

 

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

 

Fall2.JPG

 

 

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

 

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Message 2 of 6

Artur.Kosakowski
Autodesk Support
Autodesk Support

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.

 

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.

 

 



Artur Kosakowski
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Message 3 of 6

Ludwigswe
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Enthusiast

 

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.JPG

Stage one does not include mass matrix?

 

Stage Two.JPG

 

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

 

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Message 4 of 6

Artur.Kosakowski
Autodesk Support
Autodesk Support
Accepted solution

 

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!

 

modal with forces.png

 

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.

 



Artur Kosakowski
Message 5 of 6

Ludwigswe
Enthusiast
Enthusiast

Now I got it!

 

Dziekuje barza

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Message 6 of 6

Artur.Kosakowski
Autodesk Support
Autodesk Support

Smiley Happy



Artur Kosakowski
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