多跨长联连续梁桥粘滞阻尼器参数敏感性分析

Sensitivity analysis of viscous damper parameters for multi-span and long-unit continuous girder bridges

为从有利于减小固定墩地震响应的角度探讨适用于多跨长联连续梁桥的减震措施,以韩江大桥主桥(55+4×90+55)m为工程背景,研究了粘滞阻尼器对该桥抗震性能的影响。基于有限元软件ANSYS建立了全桥动力分析模型;采用Maxwell模型模拟粘滞阻尼器的力学行为;选取3条50年超越概率为2.5%的人工地震波作为地震动输入,并利用非线性动力时程分析方法,对粘滞阻尼器的力学参数速度指数α和阻尼系数C进行了参数敏感性分析;最后,将分析结果与未设置粘滞阻尼器模型的地震响应进行对比分析。分析结果表明:粘滞阻尼器在地震作用下形成了饱满、封闭的滞回环,该滞回环形状规则且包络面积较大,耗能效果良好;固定墩墩底内力和墩顶位移随着阻尼系数的增加而减小,随着速度指数的增加而增大;综合考虑粘滞阻尼器的减震效果,建议本桥粘滞阻尼器力学参数为:速度指数α取0.4,阻尼系数C取4 000 kN/(m·s^-1)0.4;与未采用粘滞阻尼器模型相比,固定墩墩底弯矩和剪力平均减震率分别为44.35%、42.52%。固定墩承受的总体水平地震荷载也降低了25%左右,并且所有桥墩承担水平地震荷载也更加均匀,所有桥墩受力更加合理。此外,还防止或减轻了上部结构顺桥向之间的碰撞以及避免了落梁震害的发生。

From the aspect of reducing seismic response of fixed pier,the vibration absorption measures of multi-span and long-unit continuous girder bridge were exploded. Taking the main bridge of Hanjiang Bridge with the span of 55+4×90+55 m as an engineering background,the seismic performance of the bridge influenced by viscous damper were studied. The finite element model for dynamic analysis of the bridge was established based on ANSYS. The mechanical behavior of viscous damper was simulated by Maxwell Model. Three artificial seismic waves with the exceedance probability of 2.5% in 50 years were chosen as the earthquake excitation. By using nonlinear dynamic time history analysis method,the parameter sensitivity analysis on velocity exponent α and damping coefficient C of the viscous damper was investigated. At last,the results were compared with the seismic response without considering the viscous damper model. All the results shown that saturated and closed lag circle of viscous damper under the action of earthquake was formed;The lag circle has regular shape,large envelope area,so that the energy dissipation effect had been proved successful. The internal force of bottom of fixed pier and displacement of top of fixed pier decreased with the increase of damping coefficient. And they also increased with the increase of velocity index. The velocity exponent α and damping coefficient C of the viscous damper were recommended as 0.4 and 4000 kN/(m · s^-1)0.4 by considering the damping effect of viscous damper.Compared with the model without viscous damper,the bending moment and shearing average damping rate of the fixed pier were 44.35% and 42.52%,respectively. The overall horizontal seismic load on the fixed pier was also reduced by about 25%,and all piers bear more uniform horizontal seismic load,the load of all piers were more reasonable. In addition,it also prevents or reduces the collision between the superstructure along the bridge direction. And the fall-beam destruction in the earthquake is avoided.