It has been observed that RC column subjected to reversed cyclic loading in orthogonal direction to eccentric moment accumulates large deformation in the direction of eccentric permanent moment through experimental work. This deformation exceeded the allowable value in design code. Analytical investigation based on 3D-fiber model has been performed to grasp the mechanism of this matter. It is verified that this behavior derives from advanced strain hardening of steel by eccentric axial forces and strongly relates to complex nonsymmetrical loading pass. This fact indicates 3D-dimensional approach is inevitable to check the residual displacement of RC piers. Moreover, it is also suggested the present design method can't possess accurate predictive value for seismic performance.