...
Here, c M and c K are the mass- and stiffness-proportional damping coefficients, M j is the mass matrix, and K j is the initial stiffness matrix. Dynamic equilibrium is then computed as the sum of stiffness forces, damping forces, inertial forces, and applied loading.
Significant differences between axial forces in axial-force discrepancy between adjacent columns expected to demonstrate similar response indicate indicates excessive damping from the c K K j contribution. This effect will magnify with shorter columns because their axial stiffness, and K j value, is larger. Given a dynamic loading condition, the cyclic bending of concrete sections will generate axial velocity. As axial extension increases with cracking and the ratcheting of yielding tensile rebar, velocity can become significant. This will cause improper damping to further effect results.
...