confused by the geometric transformation matrix
Moderators: silvia, selimgunay, Moderators
confused by the geometric transformation matrix
seems the coordinate systems are disorder in the Opensees: geometric transformation matrix
The x-axis is the axis connecting the two element nodes; the y- and z-axes are then defined using a vector that lies on a plane parallel to the local x-z plane -- vecxz.
The y-axis is defined by taking the cross product of the x-axis and the vecxz vector.
***here, the direction of y defined by this sentence is not coincide with the figure in the opensees help file.****
The section is attached to the element such that the y-z coordinate system used to specify the section corresponds to the y-z axes of the element.
The y-axis is defined by taking the cross product of the x-axis and the vecxz vector.
***here, the direction of y defined by this sentence is not coincide with the figure in the opensees help file.****The section is attached to the element such that the y-z coordinate system used to specify the section corresponds to the y-z axes of the element.
have you looked at the description in the UserManual??:
http://opensees.berkeley.edu/OpenSees/m ... sermanual/
under Model-building objects
if you scroll down on the linear transformations it is pretty clear.
Actually, it seems from your quotes that you did read the manual. The orientation vector is the same as what you learned in your finite-element analysis.
I have just reviewed the manual and I am confident that it is correct. the vector vecxz has to start at the origin, as thus you need to only specify its 3 components, vecxzX vecxzYvecxzZ.
Mathematically, I believe you can take the cross product of two vectors that do not cross (The local x axis does not have to pass through the origin, but the program has enough information to determine a vector parallel to the local x-axis), as you really just want the direction of the local y axis. The program then crosses the local x axis with the local y axis to get the local z axis. This procedure is done just so that the orientation of your section is the same as that of the element.
I hope this helps, the figures should help, too.
http://opensees.berkeley.edu/OpenSees/m ... sermanual/
under Model-building objects
if you scroll down on the linear transformations it is pretty clear.
Actually, it seems from your quotes that you did read the manual. The orientation vector is the same as what you learned in your finite-element analysis.
I have just reviewed the manual and I am confident that it is correct. the vector vecxz has to start at the origin, as thus you need to only specify its 3 components, vecxzX vecxzYvecxzZ.
Mathematically, I believe you can take the cross product of two vectors that do not cross (The local x axis does not have to pass through the origin, but the program has enough information to determine a vector parallel to the local x-axis), as you really just want the direction of the local y axis. The program then crosses the local x axis with the local y axis to get the local z axis. This procedure is done just so that the orientation of your section is the same as that of the element.
I hope this helps, the figures should help, too.
Silvia Mazzoni, PhD
Structural Consultant
Degenkolb Engineers
235 Montgomery Street, Suite 500
San Francisco, CA. 94104
Structural Consultant
Degenkolb Engineers
235 Montgomery Street, Suite 500
San Francisco, CA. 94104
Thanks!!
Thank you very much!
My only confusion now is that for Element 2, cross products of x and vectorxz has the direction to point out from the paper(i.e. the contrary direction of which y direction in the manual).
Thanks a lot!
My only confusion now is that for Element 2, cross products of x and vectorxz has the direction to point out from the paper(i.e. the contrary direction of which y direction in the manual).
Thanks a lot!