Abstract: A theoretical research work in relation to the dynamic impact effects of concrete-filled steel tubular tied-arch bridge under travelling vehicles was described.The mathematical model assumed a finite element representation of the bridge together with beam,shell,and link elements.And the vehicle simulation employed a 3 dimensional linear vehicle model with 7 independent degrees of freedom.In this way,the dynamic interaction between the bridge and vehicle model was simulated.And the dynamic amplification factors were computed for displacement and internal force respectively.The impact effects of vehicle on different bridge members and the influencing factors were studied.Meanwhile the acceleration responses of some bridge components were analyzed in the frequency domain.The dynamic amplification factors of some structural elements may exceed those specified in the design codes.And road surface roughness seems to be one of the major influencing factors.Compared to the longer hangers,the shorter ones can be ore frequently suffer from mechanical or fatigue failures.