Rayleigh波对跨V形河谷拱桥地震反应的影响

Study on the Effect of Rayleigh Waves on the Seismic Response of a V-valley Arch Bridge

为了研究Rayleigh波输入对跨越河谷拱桥地震反应的影响,以某跨越V形河谷拱桥为例,开展了Rayleigh波在V形河谷地形中传播时引起的河谷两岸的非一致激励对桥梁结构地震响应影响的研究。以SV波输入作为参考,对比了Rayleigh波和SV波作用下的河谷场地地面运动的分布特征、拱脚处地震动输入、桥梁结构内力分布规律和桥梁结构关键部位地震响应。研究结果表明:相较于SV波,Rayleigh波入射时河谷场地的地震动峰值加速度PGA分布呈现出入射一侧放大和出射一侧减小的特点,具有显著的非一致特性;在桥梁结构内力反应方面,Rayleigh波入射时的主拱圈的轴力、弯矩和剪力均显著大于SV波入射时的情况,其中轴力和弯矩的最大放大倍数在1.8倍以上,同时2种波入射时桥梁结构的轴力和弯矩在拱圈上的分布规律也有显著区别;在桥梁结构关键部位的地震反应方面,Rayleigh波入射时主要激发绕横桥向转动的振型,而SV波输入时主要激发纵桥向的振型;Rayleigh波输入时高阶振型放大系数最大,考虑到高阶振型频率对应的反应谱值更大,会出现结构反应由高阶振型起控制作用的情况。在地震动输入时考虑Rayleigh波对桥梁结构地震反应有显著的影响,在工程设计中应予以重视。

This study aimed to investigate the impact of Rayleigh wave input on the seismic response of an arch bridge across a V-shaped river valley.Particularly,this study investigated the nonuniform excitation on both sides of a river valley caused by Rayleigh waves propagating in the river valley topography.Using the SV-wave input as a reference,this study compared the distribution characteristics of ground motion at the river valley site,ground motion input at the foot of the arch,internal force distribution of the bridge structure,and seismic response of critical parts of the bridge structure under Rayleigh and SV-wave inputs.The results indicate that the PGA distribution at the river valley site exhibited significant amplification on the incident side and a decrease on the outgoing side,which has a notable nonuniform characteristic compared with SV and Rayleigh waves.Moreover,the axial force,bending moment,and shear force of the main arch ring significantly increased under the Rayleigh wave input,with the maximum amplification of the axial force and bending moment being more than 1.8 times.The distribution patterns of the axial force and bending moment on the arch ring also differed significantly between the two incident waves.In terms of the seismic response of critical parts of the bridge structure,the Rayleigh wave input primarily excited the vibration mode of rotation around the cross-bridge direction,whereas the SV wave input mainly excited the vibration mode in the longitudinal direction.Considering that for the Rayleigh wave input,the amplification factor of the higher-order mode was the largest and frequency of the higher-order mode corresponded to a larger response spectrum value,the structural response was controlled by the higher-order mode.This study highlights the significant impact of Rayleigh waves in ground vibration input on the seismic response of bridge structures and emphasizes the importance of considering this factor in engineering design practices.