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*Expert Elite* | International Moderator
Romanich
Posts: 584
Registered: ‎09-29-2009
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Seismic analysis and eccentricity

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03-14-2012 06:32 AM

Dear friends,

We have 3 type of eccentricity in Robot:

e0  -  eccentricity between center of rigidity and center of gravity. It's based on our model.

e1 - accidental eccentricity. It's equal 5% from story dimension perpendicular to the direction of a seismic action.

e2 - additional eccentricity. We can define it in properties for Modal analysis for example:

massecc.png

 

Can you explain to me how Robot take into account values of eccentricity?  It's like e=e0+e1+e2 or another?

   
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Artur.Kosakowski
Posts: 5,115
Registered: ‎12-17-2010

Re: Seismic analysis and eccentricity

03-14-2012 06:44 AM in reply to: Romanich

e1 and e2 is just the different way of defining the same parameter. It is either or choice of the way the accidental eccentricity is taken into account.

 

e = e0 + e1 or e = e0 + e2

 

See also message 2 from http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Seismic-Vs-Spectral/m-p/3361195/highlight/tr...

 

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Artur Kosakowski
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*Expert Elite* | International Moderator
Romanich
Posts: 584
Registered: ‎09-29-2009

Re: Seismic analysis and eccentricity

03-14-2012 09:26 AM in reply to: Artur.Kosakowski

Thank you Artur. 

So, if I don't use e2 (zero value in fields in properties for Modal analysis) in Seismic analysis, Robot alwas take into account e0+e1? If it's true, what is direction for eccentricity e1? I mean X+ or X+Y- etc.

Or in this case Robot use only e = e0?

   
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Artur.Kosakowski
Posts: 5,115
Registered: ‎12-17-2010

Re: Seismic analysis and eccentricity

03-15-2012 12:53 AM in reply to: Romanich

 If you don't enter any values in the parameters of modal and seismic case then e = e0.

 

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Artur Kosakowski
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*Expert Elite* | International Moderator
Romanich
Posts: 584
Registered: ‎09-29-2009

Re: Seismic analysis and eccentricity

03-15-2012 01:34 AM in reply to: Artur.Kosakowski

Ok, but it not enough clear for me.

If I didn't enter any values in the parameters of modal and seismic case, in table I'm also have values of e1:

massecc2.png

 

So I decided that the value of e1 is also used in calculations.

   
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Artur.Kosakowski
Posts: 5,115
Registered: ‎12-17-2010

Re: Seismic analysis and eccentricity

03-15-2012 02:12 AM in reply to: Romanich

I'm sorry I missed the fact that you referred to the stories table and incorrectly assumed that e1 and 2 referred to the way you define eccentricities (in a modal or a seismic case).

 

Using the values as in the table you attached e1 is just informative (not used in calculations) and is based on the 5% offset (as not used in calculations the direction is irrelevant).

 

e2 is what you define in either modal or seismic case therefore e = e0 + e2. Regarding the directions you should provide signs yourself therefore more than one modal or one seismic case in given direction may be needed. E.g. for the eccentricities defined in the modal analysis:

X 5%; Y 5%

X 5%; Y -5%

X -5%, Y -5%

X -5%; Y 5%

 

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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*Expert Elite* | International Moderator
Romanich
Posts: 584
Registered: ‎09-29-2009

Re: Seismic analysis and eccentricity

03-15-2012 02:24 AM in reply to: Artur.Kosakowski

Thanks Artur, you confirmed my conclusion.

   
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