Stiffness/Flexibility Matrix K21/F21
Input of the sub-matrix K21 (Stiffness) or F21 (flexibility)
The Matrix K21 or F21 describes the interaction between the (local) DOF's of of the end node and those of the start 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.