Learning Forum

[akbarin]

Hi everyone

I am modeling the mooring system of OC3 spar model (delta-type) and I need to define the torsional stiffness which is 98,340,000 Nm/rad. 

Is there anyone to help me how I can define the yaw stiffness for mooring line which affects time-domain results?

Cheers

[Mike Pettit]

Hello,

The easiest way to do this is to define a Connection Stiffness matrix (right-click on Connections and Insert Connection > Connection Stiffness), set Connected Structure A as your spar structure, then set the RZ-RZ term as required.

However, by default the Connection Stiffness will only be used in the Hydrodynamic Diffraction analysis. We assume that the stiffness due to moorings would usually be accounted for by actual cables in the hydrodynamic model. To include Connection Stiffness in the time domain calculations, you need to turn on the Workbench beta options. Close the Aqwa Workbench editor, and from the main Workbench page go to Tools > Options. From the list of categories click on Appearance, scroll towards the bottom of the list of settings and you should find a 'Beta Options' checkbox. Click to enable this. Then re-open the Aqwa Workbench editor.

In the Analysis Settings of the time response analysis you should now see an option to 'Include Linear Connection Stiffness Matrices'. Set this to Yes, and re-run your time domain calculation.

I hope this helps!

Mike