连续梁桥墩底自复位减隔震机理及参数优化分析

Study on Self-Centering Shock Isolation Mechanism and Parameters Optimization at Fixed Pier Bottom for Continuous Bridge

铁路连续梁桥一般只设置一个固定墩,在强震区固定墩的抗震能力难以满足需求,提出一种连续梁桥固定墩墩底自复位减隔震设计思想。在正常使用情况下,固定墩墩底与承台之间处于固接状态。在罕遇地震情况下,固定墩墩底与基础承台之间发生相对摇摆,减少了地震能量向上部结构的传递,并通过摆动过程中的相互摩擦消耗部分地震能量,起到减隔震作用。同时在地震余能和结构自重的共同作用下,使结构在震后基本能够自动恢复到初始平衡位置。以典型铁路三跨连续梁桥为例,研究了墩底自复位减隔震结构的减隔震机理,分析了墩底自复位减隔震结构主要参数对减隔震效果及滞回性能的影响。研究表明,在连续梁桥固定墩墩底设置自复位减隔震结构可以有效降低固定墩的地震响应,具有较好的减隔震效果。但在桥墩较矮时,会增大梁端纵向位移响应,在实际设计中应予以考虑。墩底自复位减隔震结构的椭圆长半径a、短半径b及桥墩高度H等参数对墩底自复位减隔震结构的减隔震效果有较大影响,而墩底自复位减隔震结构的摩擦系数μ对其减隔震效果影响相对较小。椭圆长半径与短半径之比a/b对墩底自复位减隔震结构的滞回性能有较大影响。

In general,only one fixed pier is set for a railway continuous bridge.The aseismic capacity of the fixed pier is difficult to satisfy the demand in strong earthquake area.To solve this problem,an innovative shock isolation design with a self-centering structure at the fixed pier bottom of continuous bridge was put forward.Under normal conditions,the fixed pier bottom is in a fixed state with the cushion cap.In the case of rare earthquake,the relative swing between the bottom of the fixed pier and the base platform reduces the seismic energy transmission to the bridge superstructure,and at the same time the mutual friction during the swing process can dissipate some seismic energy.At the end of earthquake,the superstructure can automatically return to the initial position under the action of earthquake residual energy and self weight.A case study of a typical 3-span railway continuous bridge was performed to study the shock isolation mechanism of self-centering structure of the pier bottom and to analyze the influence of the main parameters of the pier bottom self-centering structure on shock isolation effect and hysteretic behavior.The results show that installation of the self-centering shock isolation structure at fixed pier bottom can effectively reduce the internal force response of the fixed pier,resulting in perfect shock isolation effect.But it may increase the longitudinal displacement response of the beam end when the piers are too short,which should be considered in aseismic design.The ellipse major radius a、minor radius b and pier height H have great influence on shock isolation effect,while the friction coefficientμhas little impact on the effect.The ratio of long radius and short radius a/b has a great influence on the hysteretic behavior of the pier bottom self-centering shock isolation structure.