大跨度斜拉桥横桥向减震研究

Seismic design for long-span cable-stayed bridges in transverse direction

斜拉桥在横桥向采用塔-梁、墩-梁固结的约束体系,导致其整体刚度增加,地震惯性力增大,给边墩及其基础的抗震设计造成困难。分别采用位移相关型(方案1)和速度相关型(方案2)两类减震装置对一座斜拉桥的横桥向进行了减震研究。方案1在边墩-主梁间设置位移相关型减震装置,并对其屈服荷载进行了参数分析;方案2对速度相关型减震装置的安装位置和数量进行了优化分析,并对其参数取值进行了参数分析;对横桥向固结体系和减震体系的地震反应进行了对比。结果表明:地震作用下两类减震装置发生滞回变形,延长了结构在横桥向的周期,有效降低了边墩的地震剪力和弯矩反应;横桥向墩-梁间的相对位移会增大,可通过减震装置参数的选取将其控制在合理的范围内;塔底的地震剪力和弯矩反应变化不明显。2种方案均可用于斜拉桥横向减震。

Transverse fixed-restraints employed in the tower-girder connections and the pier-girder connections are able to increase the lateral stiffness,and amplify the inertial force of cable-stayed bridges,which makes it difficult to design the piers and their foundations.Two kinds of damping devices,displacement-dependent（scheme 1） and velocity-dependent（scheme 2）,are adopted to reduce the transverse seismic forces of a cable-stayed bridge.For scheme 1,displacement-dependent devices are utilized in the pier-girder connections and a parametric analysis of their yield loads is carried out;for scheme 2,optimization is conducted for the mounting position and the amount of velocity-dependent devices,and then a parametric analysis is carried out;seismic responses of the transverse fixed system and the damping system are compared.The results show that： under the earthquake load,the two devices could both go in hysteretic deformation and elongate the transverse period,which effectively reduces the seismic shear forces and moments of piers;the transverse relative-displacements in pier-girder connections increase,but is controlled by selecting appropriate parameters of damping devices;the seismic forces at the bottom of towers are slightly changed.The two schemes are both effective for the transverse seismic design.