Erik Kostson
Ansys Employee

 

Hi
 
See if the courses help answer some of your questions:
https://courses.ansys.com/index.php/courses/linear-column-buckling/
https://courses.ansys.com/index.php/courses/structural-instabilities/lessons/buckling-lesson-3/
 
As for the stiffness, say for a beam element in FE, the Axial stiffness term in the element stiffness matrix is (E*A_cross_section)/Length_element, and similar for bending stiffness and so on – Ansys will than assemble a global stiffness matrix by adding the contributions from all these element stiffnesses. See a book on FEA theory, the EDX Cornell University free FEA course, and or the ansys help manual for more info.