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frame Member offsets (Rigid links; RLinks)

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Message 1 of 12
sonyablade2010
2076 Views, 11 Replies

frame Member offsets (Rigid links; RLinks)

Dear All,

 

I'd like to know how the RSA is handling the offsets for frame members, for example suppose that there is an ordinary vertical column and if there are horizontal beams connecting to top node of that column with different offset settings. Then how the RSA deals with that, visual observation reveals that RSA creates artificial lever arm for differently connecting beams.

 

Your englightment will be appreciated.

 

Regards,

 

 

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Message 2 of 12

You may say that an offset is a virtual rigid link with no real generation of 'the other' node.

 

 

http://docs.autodesk.com/RSA/2013/ENU/filesROBOT/GUID-DFB075D8-BD24-4946-8D4F-3175E93DEBA3.htm

 

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
Message 3 of 12

Thanks a lot indeed,

 

So basically how this maps into FEM theory implemented in RSA, by assuming that this rigid link has same as the beam properties Ix, Iy, Iz , A,   poisson ratio etc.. except that Young Modulus is much more higher than the beam ? 

 

Is my assumption correct ?

 

 

Regards,

 

 

Message 4 of 12

For RLink approach yes, other wise the kinematic relations method (exact solution) is used.



Artur Kosakowski
Message 5 of 12

Do we have the kinematic approach in RSA? Because I haven't seen such an option in any of RSA toolbar. Can you elaborate it ?

 

Regards,

Message 6 of 12

They are used if RLinks are switched off. Mind that Sparse and Multi-threaded solvers due to their architecture force use of RLinks regardless of the setting in Job Preferences.

 

RLinks.PNG



Artur Kosakowski
Message 7 of 12
Tuctas
in reply to: sonyablade2010

  Hi,

 

  This feature in which we are able to model an offset by a kinematic constraining rather than using Rlinks is really interesting, i wasn't aware that we were able to do that..

 

  Can we do such a modeling (by kinematic constrains) for a diaphragm too? (i.e instead of assigning Rlinks between master node and slave nodes)? I mean, can we just constrain some d.o.f of selected nodes?

 

 

 

 

Message 8 of 12
Artur.Kosakowski
in reply to: Tuctas

Can we do such a modeling (by kinematic constrains) for a diaphragm too?  

 

Yes, the general rules I described above apply. You have to switch off RLinks and set the solver as Frontal, Skyline or Iterative.

 

 



Artur Kosakowski
Message 9 of 12
Tuctas
in reply to: sonyablade2010

  Thank you for your reply Artur,

 

  Do you mean that even if we model manually a diaphragm by defining manually rigid links between nodes, we can switch off the Rlinks in Job Preferences and then there would be kinematic constrains?

Message 10 of 12
Artur.Kosakowski
in reply to: Tuctas

Provided you use the solvers mentioned above.



Artur Kosakowski
Message 11 of 12
Tuctas
in reply to: sonyablade2010

  Thank you Artur,

 

  One more question about Rlink elements (I don’t know if it’s needed to make a new post with another title about that).

 

  What the help topic for RLINK type elements says that: “..provides the ability to use a concentrated mass matrix for dynamic problems does it mean that when using RLINK elements the mass that correspond to all slave nodes is transferred and concentrated to the master node? In such case are we obliged to select Lumped without rotations for the mass matrix in the Modal Analysis Parameters in order to have only diagonal non zero values in the mass matrix (when provided that all nodes of each storey of the structure are slave ones to a master node)?

 

  Thank you.  

 

Message 12 of 12
Artur.Kosakowski
in reply to: Tuctas

No, this only means that you have to use RLinks when you want to use lumped (concentrated) mass matrix for a model with rigid links.



Artur Kosakowski

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