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Load to mass conversion

23 REPLIES 23
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Message 1 of 24
Refaat
3893 Views, 23 Replies

Load to mass conversion

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

 

23 REPLIES 23
Message 2 of 24
tony.ridley
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. 

 

 

Message 3 of 24
Rafal.Gaweda
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
Message 4 of 24
Refaat
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

Message 5 of 24
Refaat
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

 

Message 6 of 24
Rafal.Gaweda
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
Message 7 of 24
Rafal.Gaweda
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
Message 8 of 24
Refaat
in reply to: Rafal.Gaweda

Dear Sir

 

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

 

Thanks

 

Rrfaat

Message 9 of 24
Refaat
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

Message 10 of 24
Rafal.Gaweda
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
Message 11 of 24
Refaat
in reply to: Rafal.Gaweda

Dear sir

 

Confirmation  >>>>>> ((seismic pseudo model(ritz)) with dynamic mass is okay ?

 

Thanks  a lot

Refaat

Message 12 of 24
Refaat
in reply to: Refaat

Dear Sir

 

As appears in the attached capture

 

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

 

Thanks

Refaat

Message 13 of 24
Rafal.Gaweda
in reply to: Refaat

 

Confirmation  >>>>>> ((seismic pseudo model(ritz)) with dynamic mass is okay ?

 

Okay

 

 



Rafal Gaweda
Message 14 of 24
Refaat
in reply to: Refaat

Dear Sir

 

As appears in the attached capture

 

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

 

Thanks

Refaat

Message 15 of 24
Rafal.Gaweda
in reply to: Refaat

 

 

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

 

I need to check the codebook. Wait.



Rafal Gaweda
Message 16 of 24
Refaat
in reply to: Rafal.Gaweda

Dear Sir

 

Could i know if you have checked the code book ? I am waiting .

(UBC97)

 

Thanks alot

 

Refaat

Message 17 of 24
Rafal.Gaweda
in reply to: Refaat


Could i know if you have checked the code book ? I am waiting .

(UBC97)

 

 

It is just a factor to multiply calculated base shear by it.



Rafal Gaweda
Message 18 of 24
Refaat
in reply to: Rafal.Gaweda

Dear Sir

 

Pls , Could u give me more explanation ?. From where can i get it  and how to calculate it?

 

Thanks

 

Refaat

Message 19 of 24
Refaat
in reply to: Refaat

Dear Sir

 

Pls , Could u give me more explanation ?. From where can i get it  and how to calculate it?

 

Thanks for your help

 

Refaat

Message 20 of 24
Rafal.Gaweda
in reply to: Refaat

1631.5.4 Reduction of Elastic Response Parameters for design.



Rafal Gaweda

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