The coordinate system

[lishhit]

The element coordinate system is specified as follows:
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. 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.
But how the axis y and z defined ? the figure followed by the says in the manual can’t match the descriptions (1:use right hand rule in local system? However,if The y-axis is defined by taking the cross product of the x-axis and the vecxz vector,it’s conflict with the rule.2: vecxz does not parallel to the local x-z plane ).
I don’t known how to do “geomTransf”.when I see Example5.1 ,beam vecxz is (1,1,0),why?
Would someone can give an example!!
Thank you.

[fmk]

we will try to make the documentation clearer .. in the meantime you can quite easily figure this out for youself .. model a cantilever with a single nonlinearBeamColumn element, create a rectangular section with elastic materials and apply the same load in the 2 orthogonal directions (y,z if member along x; x,y if member along z) .. start off using the global x,y,z axis as vectors for the coordTransformation (some won't work of course, as local x along the axis) .. look at the displacements and determine the strong and weak axis for yourself .. repeat for member lying along all major axis to make sure you understand it.

once you figured this go to s simple frame and use the 1,1,0 to see if you can see how it works .. if just use more transformations for your elements.