具自复位摩擦阻尼器的桥梁隔震性能研究

Investigation on Seismic Performance of Bridge with Self-centering Friction Dampers

目前桥梁隔震技术的应用越来越广泛,但这一技术不可避免地会引起震后桥梁上下部结构之间残余位移过大的问题。为有效降低上部结构的惯性力传递至桥墩,使其具有良好的隔震能力,同时减小上部结构复位时的阻尼,增强其自复位能力,降低震后桥梁的修复费用,提出由一种新型自复位摩擦阻尼器和聚四氟乙烯滑板支座代替传统的隔震支座。该阻尼器当活塞向远离平衡位置方向移动时,具有较为稳定的摩擦力使其具有较好的耗能能力;当活塞向平衡位置方向移动时,不具有摩擦力,减小了摩擦力对复位力的消耗,提高了其自复位能力。采用柔性拉索将此阻尼器与桥梁的上下部结构相连,保证阻尼器只受拉且可实现上部结构相对桥墩的往复运动,形成自复位隔震桥梁体系。为验证该隔震桥梁体系的效果,利用OpenSees建立一座4跨连续梁桥模型,分别配置非隔震桥梁支座、铅芯橡胶支座和自复位摩擦阻尼器与聚四氟乙烯滑板支座联合工作的隔震体系,在横桥向输入地震动记录进行时程分析,考察3种桥梁结构的墩顶位移、墩梁相对位移和桥墩内力。结果表明:在相同地震作用下,自复位隔震桥梁体系相对于非隔震桥梁墩顶位移降低为原来的1/8,墩底剪力和墩底弯矩降为原来的约1/3;与配置铅芯橡胶支座的隔震桥梁体系相比,自复位隔震桥梁体系基本没有墩梁相对残余位移。以上说明提出的自复位摩擦阻尼器及具自复位摩擦阻尼器的桥梁隔震体系有较好的隔震和自复位能力。

Seismic isolation has been already applied in bridges widely.It will inevitably cause large post-earthquake residual displacement between bridge superstructure and substructure.In order to effectively reduce the inertia force transferring to the pier to improve the ability of seismic isolation and reduce the damping force to improve the capability of self-centering,a new-type self-centering seismic isolated bridge system was proposed.This system was composed of a new type friction damper with self-centering function and the teflon sliding bearing instead of the traditional seismic isolation bearing.This new-type friction damper with self-centering function had stable friction force when the piston of the damper moves away from the equilibrium position.On the contrary,it had not friction force to reduce the consumption of the re-centering capacity when the piston moved to the equilibrium position.In addition,the bridge structure and the damper were connected by the cable in order to ensure that the damper was tensioned only and the superstructure could move relatively to the pier back and forth.In order to verify the validity of this self-centering seismic isolated bridge system,this new-type self-centering seismic isolated 4-span continuous bridge system and the same bridge structure with non-isolation bearings and lead rubber bearings(LRBs)were modelled via OpenSees.Then time history analysis was conducted for each model under the transverse ground motion record respectively.The pier top displacement,the relative displacement between pier and girder,and the internal forces of the pier were mainly investigated.Analytical results showed that the pier top displacement of self-centering seismic isolated bridge system is reduced to 1/8 and the internal forces at the pier bottom such as moment and shear force are reduced to 1/3 comparing with the non-isolated bridge.Comparing with the isolated bridge with LRBs,the post-earthquake residual displacement between the girder and the pier of the self-centering seismic isolated bridge system was very small,which indicates that the proposed new-type self-centering friction damper and the self-centering seismic isolated bridge system have better self-centering and seismic isolation capacity.