地震作用下高速铁路多联大跨连续梁桥碰撞效应研究

Study on Pounding Effect of Multi-unit Long-span Continuous Girder Bridge in High-speed Railway under Earthquake

为研究采用支座隔震设计的高速铁路多联大跨连续梁桥在地震作用下的邻梁碰撞效应,选取某铁路三联12跨预应力混凝土连续梁为实际工程背景,采用SAP2000分别建立考虑CRTSⅡ型板式无砟轨道体系的线桥一体化模型和不考虑轨道约束的传统模型,基于PEER强震数据库,选取近远场共7条地震波,考虑地震波纵向和纵向+竖向两种输入模式,首先以碰撞力峰值及碰撞次数作为评价指标,讨论了两种模型伸缩缝处的响应规律,并揭示其机理,然后考虑伸缩缝不同间隙,对两种模型的碰撞响应进行对比,最后引入碰撞影响因子,对碰撞引起的固定支座的剪力变化情况进行了分析。结果表明:不同地震波激励下碰撞特征为一次碰撞激发巨大碰撞力和多次连续碰撞;轨道系统的存在使得远场地震动下碰撞消失,近场地震动下碰撞减弱;无论邻梁碰撞反应还是碰撞对下部结构的影响,相比远场地震波,脉冲特性使得近场地震波作用效应更剧烈;考虑竖向地震动时,双曲面隔震支座动反力变化可能引起支座滑移位移增大导致碰撞效应增大;碰撞对传统模型固定墩的影响较隔震体系更明显。建议位于高烈度区以支座为隔震设计的桥梁考虑邻梁碰撞进行减隔震设计计算。

In order to study the pounding effect of adjacent beams of high-speed railway multi-unit long-span continuous beam bridge under earthquake effect,by using bearing isolation design,a 3-unit 12-span PC continuous beam on railway is taken as the actual engineering background.The integrated model considering the CRTS 11-type bal/ast/ess track system and the traditional model without considering the track constraint are established by using SAP2000.Based on PEER strong earthquake database,7seismic waves which in near and far field with horizontal input and horizontal +vertical input modes are selected.First,using the peak impact force and the number of poundings as the evaluation indexes,the response rules of the expansion joints of the 2models are discussed and the mechanism is revealed.Then,the pounding responses of the 2 models are compared considering the different clearances of the expansion joints.Finally,by introducing the pounding influencing factor,the change of shear force of the fixed support caused by the pounding is analyzed.The result shows that (1)the characteristic of pounding under the excitation of different seismic waves is a large pounding and a number of successive poundings;(2)the pounding of the far-field ground motion disappears and the pounding in the near-tield ground motion as weakenea cons^aenng track constraint ; (3)whether the pounding of adjacent beams or the influence of pounding on substructure,the pulse characteristic makes the near-field seismic effect more intense compared to the far-field seismic waves;(4) considering the vertical ground motion,the change of the dynamic reaction force of the double spherical aseismic bearing may cause the.beating slip .increasing and .then cause the increase of pounding effect;(5) the impact of pounding on the traditional fnodel fixed pier is more obvious than that on the isolated system.It is suggested that for the bridges which using bearing as the isolation design in the high seismic intensity area, the pounding effect of adjacent beams shbuld be considered in the design and calculation of seismic isolation.