Stiffness/Flexibility Matrix K12/F12
Input of the sub-matrix K12 (Stiffness) or F12 (flexibility)
The Matrix K12 or F12 describes the interaction between the (local) DOF's of of the start node and those of the end node. No input is required if one of the nodes of the element is 0.
Note: User-defined length and force units are considered, but angle unit for rotations is always Radians!
Due to symmetry the user must only enter either K12 or K21, respectively either F12 or F21.