The inelastic response of asymmetric structure subjected to bidirectional earthquake motion is studied in this paper. Fiber model is used to calculate the interaction of biaxial bending deformation in reinforced concrete columns. The effect of the system parameters on inelastic torsional response is evaluated:stiffness eccentricity es

yield strength eccentricity ep and lateral period T. The ensemble of earthquake records used consists of 6 two-component strong ground motions. The result of inelastic time-history analysis shows that: subjected to bidirectional excitation

different response occurs in stiff-side and flexible-side

with the increase of stiffness eccentricity es

the "ductility demand" of the stiff-side increase while the hysteretic energy reduces

the "ductility demand" of the flexible-side also increases with less degree than the former while the hysteretic energy increases; with the increase of strength eccentricity ep

the system subjected to bi-and uni-directional excitation response in the same trend

0<ep<es can result the best case to reduce inelastic torsion; with the increase of lateral period T

the absolute value of maximum rotation at the mass center increases

while the ratio of rotation to lateral deformation at the mass center reduces

which indicates that long-period system is slightly sensitive to bidirectional earthquake action.