Abstract：Under the strong ground motion excited by vertical earthquakes, structural damage may occur in bridges. Based on the model of a single-pier and two-span continuous bridge under vertical earthquakes, the transient wave effect approach is presented to solve the transient responses of the bridge . The numerical results show that the propagations of stress wave including reflection, reaction and wave impacts throughout the pier and the girders can be depicted. By the comparison of the seismic responses of bridge with different vertical-to-horizontal peak acceleration ratio, it is shown that the responses characteristics change obviously with increasing of vertical-to-horizontal peak acceleration ratio. Four main variations of response characteristics might take place as the ratio increase. Firstly, the fluctuating of contact force between the superstructure and the pier increases and the larger contact force may damage bridge bearing. Secondly, the smaller contact force and even the zero contact force may largely increase the possibility of the sliding between the superstructure and pier. Thirdly, the tensile stress that even exceeds the tensile strength of concrete takes place in the pier originally in whole compressed stress state when the ratio is small, and the alternating tensile-compression stress make the pier bottom in a dangerous stress state. Finally, the maximum dynamic deflection of the middle of the superstructure exceed to the deflection of the ending, implying that the superstructure may jump up.
2012, Vol. 31 
