由支座支撑的城市梁桥上部结构在强震作用下会发生较大的水平位移。为减小地震作用下主梁漂移，实现多级抗震目标，本文提出两种组合减震措施：流体粘滞阻尼器（FVD）联合板式橡胶支座（RB）减震措施，屈曲约束支撑（BRB）联合铅芯橡胶支座（LRB）多级减震措施。本研究以一座Y型墩人行钢结构连续梁桥(20m+30m+20m)为工程背景，利用OpenSees软件建立全桥模型并进行动力学分析，研究两种组合减震措施在梁桥结构中的多级抗震机理，并基于抗震机理进行了粘滞阻尼器和屈曲约束支撑的参数优化分析。主要研究内容如下：

（1）采用非线性时程分析研究粘滞阻尼器联合板式橡胶支座减震措施在梁桥结构中的多级抗震机理，提出粘滞阻尼器在不同桥宽和地震频率下的优化设计建议。研究发现，在支座支撑梁桥的墩梁之间安装粘滞阻尼器可显著降低上部结构的水平位移和支座剪切需求。进一步参数分析表明，采用适当的阻尼系数和速度指数，可以使得安装粘滞阻尼器梁桥的动力学响应对地震动特征周期不敏感。

（2）提出一种屈曲约束支撑联合铅芯橡胶支座的抗震措施，采用非线性时程分析研究其在梁桥结构中的多级抗震机理。研究发现，增加屈曲约束支撑核心区面积可显著降低主梁的水平位移和支座剪切需求，但同时也增加了桥墩的内力和位移响应。设置间隙可有效降低墩底内力和墩顶位移响应，但是会增加主梁位移和支座剪切需求。

（3）对比研究铅芯橡胶支座、屈曲约束支撑及其组合减震措施下的桥梁动力学响应，提出组合减震措施在近、远断层地震动作用下的性能优化措施。对桥墩内力、位移响应及其损伤概率等主要性能的研究表明：经过参数优化设计的屈曲约束支撑和铅芯橡胶支座的组合减震措施，既可降低主梁位移和支座的剪切需求，又可减低桥墩内力和墩顶位移。该组合减震措施适应于城市钢结构梁桥的多级抗震设防目标，具备向工程实际推广的潜力。

     The upper structure of the urban girder bridge supported by the bearings has a large horizontal displacement under strong earthquakes. In order to reduce the drift of the girder under the earthquakes and achieve the goal of multi-level earthquake resistance, this paper proposes two composite damping measures: one is fluid viscous dampers (FVD) working with plate rubber bearing (RB), the other is buckling restrained braces (BRB) working with lead rubber bearing (LRB). This research studies the pedestrian bridge with spans（20 m + 30 m + 20 m）, which is a steel structure supported by Y-shaped pier. Aiming at studying the multi-level seismic mechanism of two damping measures in bridge structure, we use OpenSees to establish the bridge model and analyse dynamic characters. Based on the above mechanism, the parameter optimization analysis of viscous damper and buckling restrained braces is carried out. The main research contents are as follows:

(1) The multi-level seismic mechanism of viscous dampers combined with plate rubber bearing damping measures in the beam bridge structure is studied by the non-linear time history analysis method, and the optimal design of viscous dampers under different bridge widths and seismic frequencies is proposed. The study found that installing viscous dampers between the piers and beams of the bearing-supported beam bridge can significantly reduce the horizontal drift of the superstructure and the need for bearing shear. Further parameter analysis shows that the dynamic response of the beam bridge with viscous damper can be insensitive to the characteristic period of ground motion by using appropriate damping coefficients and velocity exponents.

(2) ‘BRB + LRB’ is proposed for seismic resistance, and its multi-level seismic mechanism in the bridge structure is studied by way of the nonlinear time history method. The study found that increasing the core area of buckling restrained braces can significantly reduce the horizontal displacement of the girder and the shear demand of the bearing, but it also increases the internal force and displacement response of the pier. Although setting the gap can effectively reduce the internal force of the pier bottom and the displacement response of the pier top, it will increase the displacement of girder and the shear demand of bearing.

(3) This study contrasts the dynamic response of the bridge under the lead rubber bearing, buckling restrained braces and their composite damping measures and puts forward a optimization method of performance of the composite damping measures under the action of near and far fault ground motions. The research on the main performance of the pier's internal force, displacement response and its damage probability shows that parameter optimization design and the composite damping measures of ‘BRB + LRB’ not only reduce the horizontal displacement of girder and the shear demand of bearing, but also decrease internal force of the pier bottom and the displacement response of the pier top. The composite seismic reduction measure applies to the multi-level seismic fortification targets of urban steel bridges, and has potential to be popularized in the actual projects.

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