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Distinguished Contributor
refaat
Posts: 121
Registered: ‎09-17-2012

Modal Analysis Parameters

328 Views, 1 Replies
10-03-2012 11:59 PM

I want to do modal analysis for my model ( Concrete tower 21 floor) using (seismic pseudo model(ritz))

   So , my inquiries as following :

                       

01 . Which  mass matrix , I have to use to get more accurate results ?

 

02. Shall I activate (click on ) the ( disregards density  ) and ( sturm check ) when I start run to my model ?   knows that the structure mass will be (100% dead loads + 25% live loads only for parking area)

 

Thanks in advance

Refaat

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Valued Mentor
tony.ridley
Posts: 652
Registered: ‎09-07-2011

Re: Modal Analysis Parameters

10-04-2012 12:09 AM in reply to: refaat

Most accurate is consistent I believe.  But we normally use lumped with rotations.

 

If you disregard density there will be no mass participating in the modal analysis. Unless you add it back in via load to mass conversion.

 

I would NOT disregard density, and also add 30% live load (or whatever percentage) to the load to mass conversion.  Normally can ignore Z direction.  If you add mass to global or dynamic the mass will be added to all dynamic cases.  If you specify the modal case only, it will only be added to that case.

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