Primary analysis on the effect of the additional moment of center axis on the whole mechanical behaviour of a column

According to the theory of the fundamental mechanics,the mechanical mode of the bi-reinforced rectangular of concrete column is simplified,the locomotive displacement of its center axis in the cracking zone is analysed by the equation of mechanics.On the base of the analysis,the additional moment of center axis is introduced,the reason of the occurring moment is discussed and the effect of the moment on the mechanical behaviour and the stiffness of column is analysed.It is indicated that the additional moment can decrease the horizontal deformation of the column,restraine the cross section to be cracked and slow down the degradation of stiffness.So it should be considered in the seismic analysis.