BRB在双柱式桥墩抗震体系中的工作机理分析

Working Mechanism of Buckling-restrained Braces in the Seismic System of Double-column Bridge Piers

以设置防屈曲支撑(Buckling-Restrained Braces,BRB)的双柱式桥墩体系为研究对象,系统分析上部结构惯性力在该体系中的传递机理;以某3×30m公路高架桥为工程背景,采用非线性时程反应分析法研究BRB的设置方式及参数取值对桥梁地震反应的影响规律,揭示BRB在双柱式桥墩中的工作机理。其研究结论为:(1)对于设置BRB的双柱式桥墩,当BRB未屈服时,通过其轴向刚度改变结构体系的传力路径,墩底弯矩、剪力降低,但墩底轴力改变量将增大,即以较大的墩身轴力改变量换取较小的墩底弯矩及剪力。(2)在BRB屈服的情况下,BRB通过改变下部结构的传力路径及滞回耗能双重机制影响结构的地震反应,BRB耗能作用将降低墩身的轴力改变量,使减震效果更优。(3)双柱式桥墩横桥向设置BRB是一种较为有效的减震体系,但其减震效果与BRB具体布置方式及力学参数取值有关。

This study investigates a double-column pier system with buckling-restrained braces(BRB),while focusing on the transmission mechanism of the superstructure inertial force in the system.Taking a 3×30 m highway viaduct as the engineering background,the positioning of BRB and the influence of different parameters on the seismic response of the bridge were studied by a nonlinear time-history response analysis to understand the working mechanism of BRB in double-column piers.The following can be concluded from the study:(1)For double-column piers with BRB,when BRB do not yield,it changes the force transfer path of a structure through its axial stiffness,thereby decreasing the bending moment and sheer force of the pier bottom;however,the change of axial force at the pier bottom would be enlarged.(2)When the BRB yields,it influences the seismic response of the structure by changing the force transfer path of the substructure and its hysteretic energy dissipation mechanism.The energy consumption of BRB would reduce the change of axial force of the pier and optimize the damping effect.(3)Double-column pier with BRB in transverse bridge direction is an effective damping system,and the damping effect is relevant to the specific arrangement and mechanical parameters of BRB.