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

Load to mass conversion

1262 Views, 23 Replies
10-04-2012 12:02 AM

Dear Sir

 

-  Which mass type (global mass & dynamic mass ) shall I use it for my model (concrete tower 21 floor )?

 

           

Shall I activate the mass in three directions (X,Y,Z) or only (X,Y) Because my building height = 75m ?

 

 Thanks in advance

Refaat

 

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

Re: Load to mass conversion

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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Rafal.Gaweda
Posts: 5,604
Registered: ‎04-26-2010

Re: Load to mass conversion

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

 

-  Which mass type (global mass & dynamic mass ) shall I use it for my model (concrete tower 21 floor )?

 

 http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Conversion-load-to-mass/m-p/3050232/highligh... - message 3



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

Re: Load to mass conversion

10-04-2012 02:28 AM in reply to: Rafal.Gaweda

Dear Sir

I got confused about base shear coeff. ( as i see in the attached capture 01) you got this coeff. (1.74) by dividing (automatic / inactive ). Did you mean that the inactive case is the static linear case ?? (because as we know that the base shear scale is the ratio (0.85Vstatic/Vdyanmic) . as I used it in the capture 02 ,is it true or not ?

Thanks

Refaat

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

Re: Load to mass conversion

10-04-2012 02:29 AM in reply to: Rafal.Gaweda

Dear Sir

 

Pls , give me more explanation (  3 Selecting Global mass - converted masses will be applied to all dynamic cases and also can be used in inertia   forces (of course if such forces are applied on model)

  In my case , I will use (global mass ) in my model is Keya ?

 

Thanks

Refaat

 

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Rafal.Gaweda
Posts: 5,604
Registered: ‎04-26-2010

Re: Load to mass conversion

10-04-2012 03:32 AM in reply to: refaat

 

 

Pls , give me more explanation (  3 Selecting Global mass - converted masses will be applied to all dynamic cases 

 

Example:

 

lc.jpg



Rafal Gaweda
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Product Support
Rafal.Gaweda
Posts: 5,604
Registered: ‎04-26-2010

Re: Load to mass conversion

10-04-2012 03:39 AM in reply to: refaat
Refaat,

 

I got confused about base shear coeff. ( as i see in the attached capture 01) you got this coeff. (1.74) by dividing (automatic / inactive ). Did you mean that the inactive case is the static linear case ??

 

Inactive means that results come directly from seismic calculation without base shear.

 

 as I used it in the capture 02 ,is it true or not ?

 

Yes, true.

One more remark: do not use "Use normalized values" checkbox.

 



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

Re: Load to mass conversion

10-04-2012 04:23 AM in reply to: Rafal.Gaweda

Dear Sir

 

Do you mean that ( Dynamic = globle + modal ) ? , and i have to use dynamic

 

Thanks

 

Rrfaat

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

Re: Load to mass conversion

10-04-2012 04:35 AM in reply to: Rafal.Gaweda

Dear Sir

 

As appears in the attached capture

 

As I understand (T= structure period ) and what  about (reduction coeff.)?

 

Thanks

Refaat

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Product Support
Rafal.Gaweda
Posts: 5,604
Registered: ‎04-26-2010

Re: Load to mass conversion

10-04-2012 04:35 AM in reply to: refaat
Do you mean that ( Dynamic = globle + modal ) ? , and i have to use dynamic

 

Global means that converted masses will be considered in ALL dynamic cases in model (modal and footfall ones; other dynamic cases need to be run after modal case so they consider masses from precedent modal).

 

My advise: use dynamic.



Rafal Gaweda
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