双向地震作用下高铁FPS隔震简支梁桥纵向地震碰撞反应研究

为了准确分析FPS隔震桥梁的纵向地震碰撞反应,针对一典型3跨FPS隔震简支梁桥,建立了考虑FPS双向耦合效应和梁缝处三维碰撞效应的非线性动力计算模型,分析双向地震作用下FPS隔震简支梁桥纵向地震碰撞反应;研究支座半径和摩擦系数对简支梁桥纵向地震碰撞反应的影响规律。研究结果表明:横向地震作用会增大简支梁邻梁间纵向地震碰撞次数和碰撞力,降低墩底纵向剪力;为减小地震碰撞反应,设计时可适当增大支座半径和支座摩擦系数。     

基于随机振动理论确定桥梁地震碰撞的临界间隙

确定梁桥邻跨间避免地震碰撞的最小间隙,对于梁桥地震碰撞危险性预测及防地震碰撞措施的设计有着显著意义。本文基于随机振动理论建立梁桥地震碰撞邻跨临界间隙的计算方法,分析模型采用跨径不等的两跨简支梁桥,且考虑隔震支座非线性恢复力的影响。文中首先建立了系统的非线性运动方程;随后运用随机等效线性化理论将其线性化;最后在复模态空间推导了临界碰撞间隙的均值与方差的计算方法。人工地震动的非线性时程分析结果验证了本文算法的正确性。参数分析表明,临界间隙随邻跨长度比增大而增大,随支座屈服力与上部结构重量比值减小而增大,随隔震支座屈服位移增大而增大,随桥墩振动周期增大而增大。隔震支座屈服前后刚度比值对临界间隙大小影响很小。     

近断层地震特性对隔震曲线连续梁桥地震响应的影响

为研究近断层地震动对曲线连续梁桥地震响应及碰撞效应的影响,采用非线性时程分析法,分别研究脉冲效应、上盘效应及方向性效应对某三跨曲线连续梁桥支座位移、桥墩内力及邻梁间碰撞力的影响;通过支座隔震率的对比分析,探究不同类型近断层地震动下地震响应产生差异的原因。研究结果表明:脉冲效应、上盘效应和方向性效应均会增大曲线连续梁桥地震响应,脉冲效应的影响尤为显著;脉冲效应和方向性效应削弱了高阻尼橡胶支座的隔震特性,而上盘效应对桥梁响应的影响仅与上盘地震动自身特性有关;综合来看,脉冲效应对曲线梁碰撞响应影响最明显,上盘效应影响不大。     

支座形式对简支梁桥地震反应的影响

本文选取1座简支小箱梁桥,采用有限元分析软件SAP2000建立有限元模型,选择与规范反应谱频谱特性一致的实际地震记录作为输入进行时程反应分析,在墩、梁之间分别设置普通板式橡胶支座、铅芯橡胶支座和高阻尼橡胶支座,比较桥梁纵向和横向的地震反应,分析铅芯橡胶支座和高阻尼橡胶支座的减震效果,并从周期延长和能量耗散2方面分析减隔震支座的减震性能。结果表明,2种减隔震支座均可有效起到减隔震的作用,可以显著改善桥梁结构的抗震性能。     

基于系统地震易损性的桥梁隔震支座优化设计

隔震支座对桥梁抗震有重要意义,优化支座的参数可有效提升隔震效率。以一座三跨连续梁桥为例,建立了考虑桩-土-结构相互作用的有限元模型。将铅芯橡胶支座的特征强度及初始刚度视为优化变量,以最小化桥梁结构的系统地震易损性为目标。通过动力时程分析,得到支座参数对桥梁系统地震易损性的影响规律,确定支座参数的合理区间。高斯过程模型用来取代耗时的动力时程分析,降低隔震支座优化设计的计算成本。分析结果表明:铅芯橡胶支座的特征强度和初始刚度对桥梁系统地震易损性有明显影响;支座优化设计有效降低了桥梁系统地震易损性,大幅减小支座的剪切应变,提高了支座的隔震效率。     

隔震与非隔震支座对混凝土箱梁桥地震易损性的影响

为评估隔震和非隔震支座对桥梁地震易损性的影响,以一座3跨连续混凝土箱梁桥为分析对象,首先建立采用铅芯橡胶隔震支座与非隔震型盆式橡胶支座下桥梁的数值模型,求得不同程度地震作用下墩顶与支座的最大位移响应;再定义转角延性比损伤指标,结合支座剪应变,分析桥墩和支座的地震易损性情况;最后通过宽界限法建立全桥地震易损性曲线。研究结果表明,支座是较容易发生损坏的构件,而桥梁系统比桥墩或支座更易发生破坏,同时铅芯橡胶支座的破坏概率明显低于非隔震型盆式支座,可见采用隔震支座能有效减小桥墩墩顶在地震作用下的最大位移,此时桥墩地震易损性优于采用非隔震支座的情况。     

单层框架建筑模型基础隔震实验研究

对带叠层橡胶隔震基础的钢筋混凝土单层框架模型进行了振动台地震模拟试验,比较了隔震结构与非隔震结构的地震反应,结果表明,用叠层橡胶支座隔震后,框架模型的地震反应比不隔震时大大减小,证明叠层橡胶支座基础隔震技术是一种既有效又很安全的减震措施。     

复合隔震摩擦承压比的振动台试验研究

对复合隔震结构的重要参数之一摩擦承压比进行了振动台试验研究,分析试验结果表明摩擦承压比对复合隔震结构的减震效果影响很大,并且存在合理取值范围.合理的摩擦承压比取值可以使复合隔震结构的地震反应比橡胶支座隔震结构小.因此复合隔震结构具有显著的优越性.     

两种减隔震支座动力参数的设计方法及减隔震效果差异研究

为探讨强震区梁式桥减隔震支座的合理设计问题,根据设计经验归纳总结了铅芯橡胶和摩擦摆两种减隔震支座动力参数的一般设计方法及流程;针对实桥给出了两种支座的详细动力设计参数,并对参数进行了敏感性分析;根据时程分析结果对减隔震效果差异进行了对比,运用等效线性化理论解释了差异的内在原因。研究结果表明:支座摩擦系数并不是越大越有利,而应通过分析确定;由于铅芯橡胶与摩擦摆支座等效刚度值的明显不同,导致随着地震作用的提高结构内力响应差别将逐渐减小,而梁端位移响应差别呈显著增大趋势;建议高烈度区桥梁减隔震支座选型宜选用铅芯橡胶支座。     

板式支座与铅芯支座连续梁桥振动台试验对比分析

通过对分别采用板式支座和铅芯支座的2座3跨连续梁桥模型进行振动台试验,对比分析了这2类桥梁的动力特性、破坏过程及2种支座对连续梁桥地震反应的影响。研究结果表明：地震波特性对桥梁结构的地震反应有较大影响,在对桥梁结构进行抗震设计时,需选择合理的地震动输入;在地震强度较小时,板式支座的滑动能够起到一定的隔震效果,铅芯支座的隔震性能能得到较好的发挥;在地震强度较大时,铅芯支座的隔震性能不能得到很好的发挥,采用铅芯支座的桥梁地震反应不一定小于普通桥梁;通过合理的设计,2类桥梁都完全可以实现大震不倒的设防目标。     

考虑支座摩擦滑移及结构碰撞的非规则人字形桥梁地震响应分析

针对非规则人字形桥梁在地震作用下灾变严重的问题,以一座非规则人字形桥梁为研究对象,建立其空间分析模型,研究综合考虑支座摩擦滑移、结构碰撞对非规则人字形桥梁地震响应的影响。结果表明:邻梁间的碰撞作用可使得桥梁墩顶位移及内力相比不考虑时有所减小,但同时也使梁体产生了较大的加速度脉冲效应;当考虑支座摩擦滑移和结构碰撞时,固定墩墩顶位移和邻梁相对位移峰值有一定程度增大,然而对梁体加速度脉冲效应结果影响并无统一规律;纵向地震波作用下,非规则人字形桥梁不仅存在顺桥向的碰撞,横桥向的碰撞响应也不容忽视。非规则人字形桥梁进行抗震设计计算时应选取符合实际情况的计算模型,考虑支座摩擦滑移及结构间的碰撞。     

曲率半径对大温差地区小半径曲线梁桥地震响应影响分析

为研究曲率半径和近断层脉冲效应对大温差地区小半径曲线梁桥在地震作用下的动力响应和碰撞效应的影响规律,以某大温差地区曲线梁桥为研究对象,建立不同曲率半径的全桥非线性有限元模型,考虑温度变化对支座性能和伸缩缝间距的影响,开展桥梁地震响应分析.结果表明:随着主梁曲率半径增大,墩底内力响应逐渐增加,邻梁间碰撞效应逐渐增强;温度...     

Modelling three‐dimensional non‐linear seismic performance of elevated bridges with emphasis on pounding of girders

Unseating of bridge girders/decks during earthquakes is very harmful to the safety and serviceability of bridges. Evidence from recent severe earthquakes indicates that in addition to damage along longitudinal direction, lateral displacement and rotation of bridge girders caused by pounding to adjacent girders can also lead to unseating. To simulate this effect, 3D modelling of the dynamic performance of whole bridge structures, including pounding, is needed strongly. This paper presents a 3D model that is practically suitable to precisely analyse pounding between bridge girders. Experiments have been conducted to verify the proposed pounding model. The 3D non‐linear modelling of steel elevated bridges is also discussed. A general‐purpose dynamic analysis program for bridges, namely dynamic analysis of bridge systems (DABS) has been developed. Seismic analyses on a chosen three‐span steel bridge are conducted for several cases including pounding as a case study. The applicability of the proposed pounding model is illustrated by the computations. The effects of poundings on the response of bridge girders are discussed and the computation results are given. Copyright © 2002 John Wiley & Sons, Ltd.     

Implications of seismic pounding on the longitudinal response of multi-span bridges-an analytical perspective

Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes. The consequences of pounding include damage to piers, abutments, shear keys, bearings and restrainers, and possible collapse of deck spans. This paper investigates pounding in bridges from an analytical perspective. A simplified nonlinear model of a multiple-frame bridge is developed including the effects of inelastic frame action and nonlinear hinge behavior, to study the seismic response to longitudinal ground motion. Pounding is implemented using the contact force-based Kelvin model, as well as the momentum-based stereomechanical approach, Parameter studies are conducted to determine the effects of frame period ratio, column hysteretic behavior, energy dissipation during impact and near source ground motions on the pounding response of the bridge. The results indicate that pounding is most critical for highly out-of-phase frames and is not significant for frame period ratios greater than 0.7. Impact models without energy dissipation overestimate the displacement and acceleration amplifications due to impact, especially for elastic behavior of the frames. Representation of stiffness degradation in bridge columns is essential in capturing the accurate response of pounding frames subjected to far field ground motion. Finally, it is shown that strength degradation and pounding can result in significant damage to the stiffer frames of the bridge when subjected to large acceleration pulses from near field ground motion records.     

行波激励下考虑结构碰撞的非规则桥梁抗震性能研究

基于动力学基本原理,建立非规则桥梁的多自由度动力简化模型,根据拉格朗日方程推导简化模型的动力方程,结合龙格—库塔方法,采用自编程序研究行波激励下非规则桥梁综合考虑支座摩擦滑移、结构碰撞等非线性因素作用时的抗震性能。结果表明,行波效应和碰撞效应的共同作用可使矮墩的弯矩需求增大;行波激励可使板式橡胶支座位移增大,地震波最后到达的桥墩其上方支座位移峰值增加最为明显;相比高墩,地震作用下矮墩上部的板式橡胶支座易发生滑动。因此非规则桥梁进行防碰撞设计时应考虑行波激励及支座摩擦,找出相邻结构的最大碰撞力,以指导设计。     

Implications of seismic pounding on the longitudinal response of multi-span bridges - an analytical perspective

Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes. The consequences of pounding include damage to piers, abutments, shear keys, bearings and restrainers, and possible collapse of deck spans. This paper investigates pounding in bridges from an analytical perspective. A simplified nonlinear model of a multiple-frame bridge is developed including the effects of inelastic frame action and nonlinear hinge behavior, to study the seismic response to longitudinal ground motion. Pounding is implemented using the contact force-based Kelvin model, as well as the momentum-based stereomechanical approach. Parameter studies are conducted to determine the effects of frame period ratio, column hysteretic behavior, energy dissipation during impact and near source ground motions on the pounding response of the bridge. The results indicate that pounding is most critical for highly out-of-phase frames and is not significant for frame period ratios greater than 0.7. Impact models without energy dissipation overestimate the displacement and acceleration amplifications due to impact, especially for elastic behavior of the frames. Representation of stiffness degradation in bridge columns is cssential in capturing the accurate response of pounding frames subjected to far field ground motion. Finally, it is shown that strength degradation and pounding can result in significant damage to the stiffer frames of the bridge when subjected to large acceleration pulses from near field ground motion records.     

Reduction of pounding effects in elevated bridges during earthquakes

Pounding of adjacent superstructure segments in elevated bridges during severe earthquakes can result in significant structural damage. The aim of this paper is to analyse several methods of reduction of the negative effects of collisions induced by the seismic wave propagation effect. The analysis is conducted on a detailed three‐dimensional structural component model of an isolated highway bridge. The results show that the influence of pounding on the structural response is significant in the longitudinal direction of the bridge and significantly depends on the gap size between superstructure segments. The smallest response can be obtained for very small gap sizes and for gap sizes large enough to prevent pounding. Further analysis indicates that the bridge behaviour can be effectively improved by placing hard rubber bumpers between segments and by stiff linking the segments one with another. The experimental results show that, for the practical application of such connectors, shock transmission units can be used. Copyright © 2000 John Wiley & Sons, Ltd.