Base plate Stiffness Modelling

[KillianPMG]

Hi Guys,

I've used the base plate connection designer in order to size a fixed base plate. The calculated initial rotational stiffness is 568232 KN*m.

I want to model this stiffness for the main frame as my structure will be sensitive to deflection. How do I relate the value above (in Kn*m) to the value required in the support dialogue box under elastic  RY direction which is required in kN*m/deg.

Thanks in advance for your guidance regards,

Killian 

[Artur.Kosakowski · Accepted solution]

Hi Killian,

Mind that the units of rotation for stifness value shown in the steel design calculation note are set as radians ratehr than degress whichmeans you need to redefine the value you entered as the elasticity of the support. Or use the following approach instead:

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.

[KillianPMG]

Artur,

I will use your advised method.

Thanks for the quick reply, much appreciated.

Killian

[KillianPMG]

Hi Artur,

I have offsets in my model and therefore cannot not use the DSC algoritm which is required when using elastic releases.

How do I convert the rotational stiffness from the calculation note into the the rotational stiffness in degress required to use in the elastic supports defintion.

Do I need to just mulitiply the vlaue from the calculation note by 3.14/180 and insert the values into the support section attachde.

Regards

Killian

[StefanoPasquini6790]

Hi,

Try to use rigid links instead of offsets.

Greetings

[KillianPMG]

Hi,

I had originally used rigid links but I reverted to offsets as I was get waarning when runnning model. I believe this was due to different in the very stiff rigid link members causing issues during the calculations.

Killian

[Artur.Kosakowski]

I have offsets in my model and therefore cannot not use the DSC algoritm which is required when using elastic releases.

How do I convert the rotational stiffness from the calculation note into the the rotational stiffness in degress required to use in the elastic supports defintion.

Do I need to just mulitiply the vlaue from the calculation note by 3.14/180 and insert the values into the support section attachde.

I'm not sure if I understand this situation correctly. Do you have a column with a support in its bottom node and you want to apply an offset to this column? In such case you will get an additional bending moment in the support and I'm not sure if for such situation the value you get from the steel connection applies. To be honest personally I would avoid using offsets for columns and I'd rather model it in the "right" position (directly over the support) and use rigid link to connect it with the remaining par of a model. This approach is illustrated in the post 4 from http://forums.autodesk.com/t5/robot-structural-analysis/supports-outside-the-central-axis/td-p/55347...

The value in the steel connection module assumes radians as rotations so you need to convert it to degrees or change the units of rotations to radians.

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.

[KillianPMG]

Hi Artur,

Thanks you for reply.

Can I send you the model via customersupport@autodesk.com. I would like you to review what I have done,

Unfortunately we replaced the rigid links as I was getting instabilities due to the large difference in stiffness and therefore applied offsets instead. The column is centred over the support and the top half half is offset.

Regards

Killian

[Artur.Kosakowski]

Hi Killian,

Check your mailbox please.

[KillianPMG]

Thanks Artur, I have sent file.

Killian

[athurD]

Hi @Artur.Kosakowski 

Can you Attachment your approach , This pictute erro I can't see it.

Thanks.

[athurD]

Hi Support,

Please help below.

How do I relate the value above (in Kn*m) to t kN*m/deg.

Thank so much