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Valued Mentor
tony.ridley
Posts: 653
Registered: ‎09-07-2011
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Damping for seismic and spectral cases.

495 Views, 5 Replies
09-24-2012 06:12 PM

Hi guys,

 

  • If I include damping in modal case that precedes the Spectral case, do I need to add a value for damping in the spectral definition?   If I include damping in the spectral definition and also check on damping in modal, does Robot "double up" on damping?

 

  • In the AS1170 seismic, there is no damping definition.  Do I need to check it on in Modal definition for it to be included?

Tony

 

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Product Support
pp2008
Posts: 529
Registered: ‎06-23-2008

Re: Damping for seismic and spectral cases.

09-25-2012 07:30 AM in reply to: tony.ridley

Hi Tony,

some summary on using damping in  modal, spectral and seismic cases.

 

Damping defined in advanced parameters of modal case

damping in modal.png is used in:

1/ damping correction of elastic spectra in these seismic codes where it is possible - for instance in EN-1998-1-1 (Eurocode 8)

2/ in calculation of complete quadratic combinations (CQC) and double sum method (2SM) combinations - see appropriate Help topic

 

Damping defined in spectral analysis is not used directly in spectral analysis calculations- it can be treated as some identifier of various spectra here. It is used  when preparing spectra in case of spectra interpolation:interpolating spectra.png

 

 

Above settings correspond to different actions so there is no risk to consider damping "twice".

 

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Regards,



Pawel Pulak
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Valued Mentor
tony.ridley
Posts: 653
Registered: ‎09-07-2011

Re: Damping for seismic and spectral cases.

09-25-2012 05:41 PM in reply to: pp2008

Hi Pawel thanks for your reply.  What about this damping setting:

Capture.JPG

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Product Support
pp2008
Posts: 529
Registered: ‎06-23-2008

Re: Damping for seismic and spectral cases.

09-26-2012 12:15 AM in reply to: tony.ridley

This damping setting would be used only when using this spectra in Spectra Interpolation:

damping in spectral.png

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Regards,



Pawel Pulak
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Valued Mentor
tony.ridley
Posts: 653
Registered: ‎09-07-2011

Re: Damping for seismic and spectral cases.

09-26-2012 06:43 PM in reply to: pp2008

Thanks for your reply Pawel,

 

Perhaps the dialogue box should be removed from it's current position, it's a bit misleading. 

 

Thanks anyway,

Tony

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Product Support
pp2008
Posts: 529
Registered: ‎06-23-2008

Re: Damping for seismic and spectral cases.

10-01-2012 02:58 AM in reply to: tony.ridley

Hi Tony,

sorry for incomplete/incorrect answer in my previous post:

damping from properties of spectra is used in spectra averaging not only in spectra definion but also when using averaged spectra directly in spectral load case - see the screen capture below:

spectra averaging.png

 

In such case the actual relative damping used to calculate averaged spectra will be taken from advanced parameters of modal case preceding this spectral case.

 

---------------------------------------------
If this post answers your question please click "Accept as Solution". It will help everyone to find answer more quickly!

 

Regards,



Pawel Pulak
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