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Output of Sensor in sub structure
Hi,
I wanted to know the cooridnate system of the output force in the members of the jacket from Qblade?
additionally, Are the output force internal force of the member?
As far as my limited knowledge, the force at the two ends of any member should be in equilibrium if they are internal force.
Can anyone please clarify these points
Hi,
the output forces are given in the local beam coordinate system (see also here). You can check the coordinate system orientation of a beam in the GUI when toggling the “Struct. Coord Sys” button in the Dock.
You could interpret the local x-y forces as the shear forces, the z-force is the longitudinal force. The moments are internal benidng moments and the torsional moment.
The forces at member ends dont necessarily need to be in equilibrium, they depend on the boundary conditions at the connection point.
BR,
David
Hi,
Thanks for the reply.
Consider the member in the attachment, when i take forces at either end of this member according to my understanding they should be in equilibrium. But that is not the case.
Can you please explain more regarding the boundary condition at the connection point that you mentioned.
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Hi,
an equilibrium of forces must exist at the interface between two or more members, as every action force results in a corresponding reaction force, ensuring the overall structural system remains in a state of equilibrium.
However, while the overall structure should be in equilibrium, this does not imply that individual members are free of internal forces or moments.
Instead, the forces acting on an individual member result from the boundary conditions applied at its ends (such as fixed, free, or pinned supports) and the distributed loads acting along its length (such as hydrodynamic drag, gravitational forces, etc.).
These forces and moments must be balanced globally for the structure to be in equilibrium, but they can vary significantly along the length of each member depending on the specific conditions and loads applied.
BR,
David
Thank you for the clarification.
One more question, Is it possible to apply any point loads in the structure somehow. For example if i dont want to use the wind turbine and want to directly apply the loads at TP. Is that possible ?
Hello,
yes, thats possible. You can checkout the Turbine Behavior section the the documentation.
Through an “External Loading File” you can assign a time varying (or constant) load to any joint of the substructure. To apply a load to the transiiton piece you simply create a joint at the TP location and then constrain it to the TP.
The location ID you need to use in the loading file is JNT_X, where X is the ID of the joint connected to the TP.
BR,
David
Hi,
They way that you described to introduce load on the jacket doesnt seem to work. I have isolated the model, there are no loads execpt for the external loading file. But in the output, I dont see any forces at the Boundary Conditions.
I have attached the .qpr file. Can you please guide me.
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Hi,
in fact, there is nothing wrong with the project that you have provided – but the issue is with QBlade.
Two issues in the code:
- External loading files are not read when using a substructure only (as in your case)
- The JNT_X IS is not correctly assigned via the external loading file
I have already fixed the issues for the upcoming release, until then you can try the following:
- Load the Jacket model through the main file (not the substructure file), remove tower and blades and then apply the load directly at the hub, using the HUB keyword.
Check out the attached project, which implements these changes!
It is also possible to assign a load directly to a substructure member using the SUB_ID_POS keyword (such as SUB_23_0.5, applying the load to member 23 at its mid-position).
BR,
David
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Hi,
Thanks a lot David for the help.
I want to ask. If i read the forces at the lowest legs of the jacket at 0 length. That should give me the total reaction force ?
or do i need to sum the internal forces for each member to get the total force?
