Autodesk Robot Structural Analysis

[#1]

Rafal/Artur,

How are you guys today?

I have a model with beams, columns and panels, and I generate the model using;

     Analysis----->Analysis Types--------->Structure Model-------->Generation of Computation Model

Lets say I have deal load (1), super dead (2), and live load (3) cases.  While I'm making sure the model works OK, I set the second 2 cases to auxilliary.  After I'm happy with the model under dead load only, I want to add the other cases.  I have node loads and planar loads in the 2nd and 3rd cases. 

1st Question:

Do I need to regenerate the computational model before I run the 2nd and 3rd cases?  Or if I calculate without generating the model, will it work OK??

2nd Question:

If I have run the first 3 cases (and done model generation) but then I want to add modal and spectral, do I need to regenerate the computation model?

Thanks as always,

Tony

[#2 · Accepted solution]

1st Question:

Do I need to regenerate the computational model before I run the 2nd and 3rd cases?  Or if I calculate without generating the model, will it work OK??

IN case of only nodal loads added - no need to generate model. Otherwise yes.

2nd Question:

If I have run the first 3 cases (and done model generation) but then I want to add modal and spectral, do I need to regenerate the computation model?

Yes. Masses must be generated.

[#3]

---

Lets say I have deal load (1), super dead (2), and live load (3) cases.  While I'm making sure the model works OK, I set the second 2 cases to auxilliary.  

One more remark about combinations with aux case.

If the model is linear - combination combines results so if combination contains aux case you will not get results for such combination because there are no results in aux case

If the model is nonlinear or at least the combination with aux case is nonlinear - combination combines forces from all cases from its definition so after calculations you will get results.

[#4]

2nd Question:

If I have run the first 3 cases (and done model generation) but then I want to add modal and spectral, do I need to regenerate the computation model?

Yes. Masses must be generated.

OK.  

So if I run modal and don't get enough modes, or want to change the direction factor in spectral, or change the factor in load to mass conversion, do I need to regenerate the computation model?

Cheers,

Tony

[#5]

Hi Tony,

 if I run modal and don't get enough modes, 

Try Calculation Restart option.

[#6]

So if I run modal and don't get enough modes, or want to change the direction factor in spectral, or change the factor in load to mass conversion, do I need to regenerate the computation model?

No.

I do not recomend such actions because in the meantime you can make changes in model and they will not be considered in calculation.

This can be helpful also:

http://docs.autodesk.com/RSA/2012/ENU/filesROBOT/GUID-8E0F5493-49E9-4363-B33D-5D8077A10C9-606.htm

[#7]

Thanks Romanich, I have used this one before.

 But it occured to me that if I had already unchecked the generate computation model that it might give an error.

[#8]

So if I run modal and don't get enough modes, or want to change the direction factor in spectral, or change the factor in load to mass conversion, do I need to regenerate the computation model?

No.

Sorry Rafal,  to clarify, do you mean "no, you don't need to re-run the model generation" or "no, don't do it"?

Cheers,

Tony

[#9]

---

tony.ridley wrote:

So if I run modal and don't get enough modes, or want to change the direction factor in spectral, or change the factor in load to mass conversion, do I need to regenerate the computation model?

No.

Sorry Rafal,  to clarify, do you mean "no, you don't need to re-run the model generation" or "no, don't do it"?

 "no, you don't need to re-run the model generation"

[#10]

OK.......so the first time I define a modal analysis and assign load to mass conversion, the loads are converted to masses during the initial model generation.  If I then modify the conversion factor, it is just scaled from the previous calculation?  Sorry to keep asking the same question in a different way.