Local coordinates
Local coordinates
what is the meaning of the local coordinates? and why should we use the local coordinates especially when adding the inteaction?
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marafini.f
- Posts: 363
- Joined: Fri Nov 13, 2020 1:52 pm
Re: Local coordinates
Hi spater,
In OpenSees there is the concept of geometric transformation, which if you are not familiar with I can suggest you watch this video at min 28:05
https://www.youtube.com/watch?v=w8FCrWkeSyI
This construct in OpenSees it serves the purpose to move from the local coordinate system to the global one.
Each geometric element in STKO has a local coordinate system, vertices have a system collapsed in one point, edges have a 3D system with a characteristic axis "x" along the edge itself and faces have also a 3D system, with the "z" axis normal to their surface. This system has the purpose to orient the geometric elements in the global space, and for example for beam elements, arrange the section around the edge.
There is a default in which this local coordinate system is assigned to geometry in STKO, and most of the time you don't need to change them or adapt them. If you want to change the orientation of the characteristic axis, you can use the Reverse command (x for edges, z for faces). If you want to change how the other 2 axis are positioned with respect to the characteristic one, you should create a new local axis system from the work tree.
Interactions too have a local axis, and this could be relevant whenever you want to apply an element or a condition that has a local directionality, like for example contact elements. If you are using a rigidDiaphragm, the local axis orientation does not matter, as you indicate a global DOF in its definition.
If you need additional info let me know.
Enjoy your modeling
Francesca
In OpenSees there is the concept of geometric transformation, which if you are not familiar with I can suggest you watch this video at min 28:05
https://www.youtube.com/watch?v=w8FCrWkeSyI
This construct in OpenSees it serves the purpose to move from the local coordinate system to the global one.
Each geometric element in STKO has a local coordinate system, vertices have a system collapsed in one point, edges have a 3D system with a characteristic axis "x" along the edge itself and faces have also a 3D system, with the "z" axis normal to their surface. This system has the purpose to orient the geometric elements in the global space, and for example for beam elements, arrange the section around the edge.
There is a default in which this local coordinate system is assigned to geometry in STKO, and most of the time you don't need to change them or adapt them. If you want to change the orientation of the characteristic axis, you can use the Reverse command (x for edges, z for faces). If you want to change how the other 2 axis are positioned with respect to the characteristic one, you should create a new local axis system from the work tree.
Interactions too have a local axis, and this could be relevant whenever you want to apply an element or a condition that has a local directionality, like for example contact elements. If you are using a rigidDiaphragm, the local axis orientation does not matter, as you indicate a global DOF in its definition.
If you need additional info let me know.
Enjoy your modeling
Francesca