## MAxwell reciprocal theorem and symmetric stiffness matrix

As per Maxwell reciprocal theorem, it is valid only for elastic materials and structures indergoing small displacements.That is k12 = k21, kij = kji hence stiffness matrix is symmetric.

Howbver, I just have been going through MY OWN written programs for geometric non linear problems and I observe that stiffness matrix (assembled stiffness matrix) is well symmetric.

How can stiffness matrix be symmmetric for non linear behaviour of structures?
 Perhaps if you posted an example? What elements do you have in your matrix? kij is just a constant and therefore linear.
 I have beam elements in my matrix. It is a cantilever beema with end moment.