Composite Sections

[sirwan]

Hi
I have some questions regarding defining a composite section using fiber section command
1-When I define the geometry of the section using patch command, should I give the coordination of nodes according to the local axes (located at the geometric center) of the whole section, or I need to define it based on the actual local axes which is shifted away from the geometric center of the section due to the different materials used for the patches? (Does OpenSees automatically consider the effect of different materials and calculates the real position of principle axes or not?)
2- how the local axes of a section are arranged in a 2d frame? which one is the main?

[fmk]

1. do either, results will be the same.
2. bending about yy

[sirwan]

great! thanks so much!