Rayleigh Damping

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jovillarroelb
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Joined: Mon Aug 06, 2012 9:43 am
Location: Universidad de Chile

Rayleigh Damping

Post by jovillarroelb »

Hi;

I'm modeling a bridge and I need to set the modal damping 2% por the first 2 modes and for the rest 5%. How can I do this for time history? Raileigh damping?

Thanks!
fmk
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Re: Rayleigh Damping

Post by fmk »

you can't. in rayleigh damping you can only specify damping ratio for 2 modes. you might as well take a look at the theory to understand what rayleigh damping is before you use it.
Panos
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Location: National Technical University of Athens

Re: Rayleigh Damping

Post by Panos »

In order to assign damping values to 3 or more vibration modes, you have to use Caughey damping, but I do not know if such an option is available in opensees.
fmk
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Re: Rayleigh Damping

Post by fmk »

it's not. the reason os it leads to a full system of equation matrix which can only be used to solve trivial problems due to memory requirements.
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