近断层地震动对上承式拱桥动力响应的影响

为了揭示近断层地震作用下上承式钢筋混凝土拱桥的动力响应特点，以西南山区某上承式拱桥为背景，用OpenSEES平台建立了全桥非线性动力分析模型，探讨了近断层地震动的输入方式、脉冲效应和竖向地震动等三个关键因素对桥梁动力响应的影响规律。研究结果表明:地震输入方式对拱圈地震响应的影响较小，但对拱上立柱地震响应的影响很大，尤其是拱顶附近的短立柱，在抗震分析中，建议偏安全地采用三向地震输入方式；脉冲效应对拱桥地震响应的影响非常大，会导致拱圈、拱上立柱和桥面板地震响应大幅增加，桥面板残余平面转角甚至增大6倍以上；竖向地震动对拱圈轴力和面内弯矩、拱上立柱纵向弯矩和剪力的影响很大，拱顶处的面内弯矩放大倍数最大可达2.95，总体来说，采用规范所建议的方法考虑竖向地震是偏保守的。

Effect of near-fault ground motions on seismic response of deck-type arch bridge

In order to reveal the dynamic response characteristics of a deck-type reinforced concrete arch bridge under near-fault earthquakes,a deck-type arch bridge in Southwest China was taken as a background engineering, and a nonlinear dynamic analysis model was established for the entire bridge structure using the OpenSEES code. The effects of the three key factors,i.e.,excitation input modes,impulse and vertical motions,of the near-fault earthquakes were examined on the dynamic responses of the background bridge. The research shows that the seismic input method has a small impact on the seismic response of the arch ring,but has a great impact on the seismic response of the pillar on the arch,especially the short pillar near the arch. In the seismic analysis,it is recommended to use the three-way method safely;the impulse effect has a great influence on the seismic response of the arch bridge,which will cause a significant increase in the seismic response of the arch ring,the pillar on the arch and the bridge deck,and the residual plane angle of the bridge deck can even increase by more than 6 times;the vertical ground motion affects the arch ring axial force and in-plane bending moment,longitudinal bending moment and shear force of the pillar on the arch have a great influence. The in-plane bending moment at the vault can be magnified up to 2.95. There is no obvious law between the method of reducing the horizontal ground motion as the vertical ground motion and the result calculated by the original vertical ground motion. The reduction method needs further study.