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Valued Contributor
jo2ny
Posts: 82
Registered: ‎02-07-2012
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Incorrect masses ?

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11-12-2012 03:57 AM

Hello,
I'm having trouble with the masses participating to modal analysis.
In order to avoid any other errors i defined a single load (33 Masses) specialy for load to mass conversion.
I set the Direction -z, coef. = 1.00 , ->global masses


The 33Masses load is uniformly distributed at the roof level.

 

After i run the calculation, in the Dynamic Analysis Results table i get the Total Mass = 14442 Kg.
The mass participation for the first mode (UY direction) is only 65%.
BUT, the total UZ reactions for 33Masses load is 61kN;

 

Q1: Why is the toatal weight from 33Masses (=61kN) converted in 14442 Kg mass? Shouldn't it be ~6100 Kg ?

Q2: The roof elements are the only ones loaded with 33Masses. I also added a ridgid diaphragm at the roof level. Why is only 65% of the total mass participating in the first 3 modes?

 

I couldn't attach my model but you can find it here. http://dl.transfer.ro/transfer_ro-12nov-10a5ae9b2b8744cd.zip
Thank you in advance!

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Rafal.Gaweda
Posts: 5,498
Registered: ‎04-26-2010

Re: Incorrect masses ?

11-12-2012 04:07 AM in reply to: jo2ny

 

Q1: Why is the toatal weight from 33Masses (=61kN) converted in 14442 Kg mass? Shouldn't it be ~6100 Kg ?

 

It is like that - see below:

 

masses.jpg

 



Rafal Gaweda
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Product Support
Rafal.Gaweda
Posts: 5,498
Registered: ‎04-26-2010

Re: Incorrect masses ?

11-12-2012 04:09 AM in reply to: jo2ny

Q2: The roof elements are the only ones loaded with 33Masses. I also added a ridgid diaphragm at the roof level. Why is only 65% of the total mass participating in the first 3 modes?

 

Take a look at screen shot above - 98/100 % after first 2 modes without considering selfweight.

 



Rafal Gaweda
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Valued Contributor
jo2ny
Posts: 82
Registered: ‎02-07-2012

Re: Incorrect masses ?

11-12-2012 04:53 AM in reply to: Rafal.Gaweda

Thank you so much!

 

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