限位装置对滑动摩擦隔震桥梁地震反应的影响研究

为防止滑动摩擦隔震桥梁位移过大对临跨造成不利的影响,可在桥墩上设置限位装置限制墩梁相对滑动位移,降低滑动摩擦隔震桥梁的纵向位移。本文提出了滑动摩擦隔震支座和限位装置同时使用的抗震构造措施,利用滑动摩擦隔震支座降低固定墩的地震反应,利用限位装置降低墩梁相对滑动位移。建立了同时考虑支座滑动摩擦非线性、限位装置接触碰撞及其材料非线性和桥墩材料非线性的桥梁结构非线性地震反应分析模型,改变活动支座摩擦系数、限位装置与梁体之间的碰撞初始间隙等参数,进行了非线性时程反应分析,针对限位装置对滑动摩擦隔震桥梁的非线性地震反应的影响进行了综合分析。研究表明,限位装置对于限制滑动摩擦隔震桥梁的梁部位移、均衡地震动输入能量在各墩之间的分配有着较大的作用。设计时可通过详细的有限元分析,改变限位装置的间距、刚度等设计参数,使限位装置起到降低滑动摩擦隔震桥梁的纵向位移而不显著增加固定墩地震反应的作用。     

非规则梁桥纵向地震反应及碰撞效应

针对我国西部山区典型的非规则梁式桥梁 ,采用非线性时程地震反应分析方法 ,探讨了纵向地震作用下非规则梁桥相邻联的非同向振动特性和伸缩缝处的碰撞效应。结果表明 :当梁式桥相邻联周期相差较大时 ,纵向地震作用下 ,会导致伸缩缝处相邻梁体较大的相对位移和碰撞 ,碰撞导致低墩地震反应增大 ,对结构抗震不利。还提出了减小相邻联非同向振动和伸缩缝处碰撞效应的措施和方法     

地震作用下大跨斜拉桥主桥与多联引桥伸缩缝处连锁碰撞效应研究

针对地震作用下大跨斜拉桥主桥与多联引桥间易发生连锁碰撞现象,以一座典型大跨斜拉桥为研究背景,采用SAP2000 Nonlinear有限元程序,建立考虑主桥与多联引桥伸缩缝处碰撞效应的桥梁结构三维非线性计算模型,采用非线性时程分析法,研究大跨斜拉桥主桥与多联引桥伸缩缝处连锁碰撞效应对桥梁抗震性能的影响,并分析初始间隙、引桥周期比对连锁碰撞效应的影响规律。研究结果表明:若仅在引桥-引桥相邻梁体间发生碰撞,碰撞效应对短周期联引桥影响不大,但对长周期联引桥有一定影响,即会增大长周期联引桥梁端位移、梁墩相对位移以及固定墩墩底地震响应;而若主桥与多联引桥间发生连锁碰撞,不仅会显著增大短周期联引桥梁端位移、梁墩相对位移以及桥墩地震响应,而且会进一步增大长周期联引桥梁端位移、梁墩相对位移以及桥墩地震响应,更易引起各联引桥桥墩破坏或梁体落梁;随着初始间隙的增大,连锁碰撞效应对引桥结构的影响减弱;随着短周期联引桥基本周期的减小,连锁碰撞效应对短周期联的影响也有所降低。     

附加限位装置对钢管混凝土拱桥的减震效果

以某钢管混凝土拱桥为工程背景,在动力特性和反应谱分析结果的基础上,分析其在地震荷载作用下主桥伸缩缝处采用限位装置后的结构地震响应。研究结果表明,附加限位装置能显著减小伸缩缝处相邻桥面系的相对位移,提高结构的抗震安全性。     

桥台伸缩缝处的碰撞对地震反应的影响

连续梁桥在地震作用下,伸缩缝处发生碰撞而造成结构破坏。本文在建立考虑桥台与梁之间碰撞效应的简化刚体模型的基础上,采用有限元分析软件ANSYS对模型进行地震反应时程分析,研究了在考虑桥台与梁之间碰撞作用下,纵向地震作用时梁与梁伸缩缝处的碰撞效应。并分析了梁与桥台的碰撞对桥梁结构位移的影响,研究结果对类似的连续梁桥的抗震设计有一定的参考价值。     

非规则梁桥伸缩缝处的碰撞对地震反应的影响

针对非规则梁桥在地震作用下伸缩缝处的碰撞现象,在建立考虑双边碰撞效应的简化动力分析模型的基础上,采用非线性地震反应时程分析方法,研究了纵向地震作用下非规则梁桥伸缩缝处的碰撞效应,并分析比较了双边碰撞与单边碰撞对桥梁结构位移的影响,研究结果对同类型的非规则梁桥的抗震设计具有一定的参考价值。     

采用拉索模数伸缩缝的连续梁桥地震响应

针对多跨连续梁桥在地震作用下发生的落梁和碰撞等震害,采用了拉索模数伸缩缝限位装置。对拉索模数伸缩缝的工作原理及其有限元模拟进行了简单的介绍;以一座典型的三联连续梁桥为背景,建立了该桥有限元模型;分析了不同场地、烈度条件下该桥3种体系的地震响应:联间相对位移、墩梁相对位移和墩底剪力。结果表明:在不同场地、烈度下,拉索模数伸缩缝能有效限制联间梁体的相对位移,避免碰撞发生;同时,将拉索模数伸缩缝与拉索支座结合的体系不仅能够限制联间和墩梁相对位移,而且使地震力在各个墩的分布更加均匀,真正实现了力与位移的完美协调。     

桥梁中抗震限位装置设计方法的研究

目前,地球的形势越来越严峻,人类所面临的挑战也越来越多,特别是自然灾害,比如说地震。在地震中,桥梁联结间的伸缩缝处就会发生过大变位的情况,因此成为造成桥梁破坏的直接原因,所以就需要在支座宽度不是特别大的伸缩缝间设置一个适当的限位装置,用来限制伸缩缝间的相对位移。本文通过对限位装置设计的方法进行了研究,从而达到其限位的目的。     

橡胶伸缩缝对连续梁桥地震反应的影响

以一座三联连续梁桥为原型,建立考虑橡胶伸缩缝弹性刚度的简化动力分析模型,研究了伸缩缝弹性刚度对结构动力特性的影响;并采用线性时程分析方法在四类不同场地条件下研究了伸缩缝刚度变化对结构地震反应的影响。研究结果表明,橡胶伸缩缝弹性刚度增加能有效限制由相邻联相向运动产生的纵向相对位移从而防止碰撞,伸缩缝刚度在一定范围内变化可以减小墩、梁相对位移,但是可能对固定墩的剪力、弯矩带来不利影响。     

地震作用下城市高架连续梁桥碰撞单元刚度参数分析

本文基于Kelvin碰撞单元建立3联城市高架连续梁桥地震碰撞分析模型,采用非线性时程方法对碰撞单元刚度的取值进行了参数分析。分析结果表明:当碰撞单元刚度较小时,相邻梁体间的碰撞力受碰撞单元刚度影响较大,单元刚度取值对于相邻联梁体最大相对位移影响不大;而当碰撞单元刚度大于1联梁体的2倍轴向刚度时,碰撞力和位移的计算结果随碰撞单元刚度的增加变化不超过10%。     

Pounding mitigation and unseating prevention at expansion joints of isolated multi-span bridges

Damage of adjacent bridge structures due to relative responses, such as pounding and unseating, have been observed in many earthquakes. The isolators in bridge structures are effective in mitigating the induced seismic forces. However, the deck displacement becomes excessively large when subjected to ground motion with unexpected characteristics. This increases the possibility of pounding; and contributes to the unseating of bridge decks and subsequent collapse. An analytical model of expansion joints, that takes account of the interaction between adjacent bridge segments and the effect of impact and restrainers, is developed and nonlinear time history analyses are performed on a typical isolated multi-span bridge using three standard ground motions. The numerical simulation results show that pounding between adjacent bridge segments could amplify the relative displacement, resulting in the requirement of using an unseating prevention system. Restrainers are substantially effective in reducing the relative opening displacements and impact forces due to pounding at the expansion joints. However, the impact and the stretch of cable restrainers at expansion joints results in a large lateral force transfer from one deck to the other, which, consequently, significantly changes the global response of the participating structural systems. Therefore, it is effective to provide a shock absorber for the mitigation of impact effects between bridge segments or at the restrainers’ ends. The sudden changes of stiffness during poundings can be smoothed by using a natural rubber shock absorber, which prevents, to some extent, the acceleration peaks due to impact. The reaction forces at the pier bases and the pounding forces exerted on the superstructure can be satisfactorily reduced.     

Numerical assessment of new compound restrainer for seismic retrofit of bridges

This paper studies through numerical simulation a practical compound restrainer to use for the improvement of seismic performance of bridges. A mechanical model has been introduced for the restrainer and a basic optimisation approach has been conducted to evaluate the performance of the restrainer to changes in the properties of its components. A real 2-span simply supported plate girder bridge has been selected for case study. Using a detailed three-dimensional model, several non-linear time history analyses were performed under seismic excitations in order to assess the performance of the bridge retrofitted by conventional restrainers including linear and non-linear viscous dampers on one hand and the new compound restrainer, proposed in this study, on the other hand. The results illustrate the effectiveness of the proposed compound restrainer in improving the seismic performance of the bridge by restricting its lateral displacement and applying smaller loads to the substructure. Moreover, noticing past earthquakes have shown the deficiencies of conventional restrainers, the new restrainer seems a suitable alternative since it has been successful in dissipating significant amount of seismic energy as well as reducing the internal forces induced in substructure.     

Seismic performance of isolated curved steel viaducts equipped with deck unseating prevention cable restrainers

This paper presents an in-depth analysis to evaluate the efficiency of using cable restrainers connecting isolated and non-isolated spans for preventing unseating of curved steel viaducts. For this purpose, the overall three-dimensional non-linear bridge response is examined in detail under the action of strong earthquake ground motions. The expected seismic vulnerability of bridge structures with curved deck geometries has been demonstrated, providing a refined estimation of seismic demands on most critical bridge components. The advantage of using a precise three-dimensional model has revealed the concentration of large seismic forces on specific steel bearing supports and cable restrainer units that greatly increase their failure possibility. Moreover, the unbalanced distribution of pounding forces found across the expansion joint is able to cause local damage to colliding girders and transmit high impact forces to bearing supports. In general, restrainers perform effectively to minimize the possibility of deck unseating and reduce the pounding forces at the expansion joint. Special attention should be paid to the non-linear bridge dynamic response in order to avoid failure of restrainers and ensure the adequate proportioning of the cables according to the characteristics of isolation bearings.     

Devices for protecting bridge superstructure from pounding and unseating damages: an overview

Previous earthquakes have highlighted the seismic vulnerability of bridges due to excessive movements at expansion joints. This movement could lead to the catastrophic unseating failure if the provided seat width is inadequate. Moreover, seismic pounding is inevitable during a strong earthquake due to the limited gap size normally provided at the expansion joints. Various types of restrainers, dampers and other devices have been proposed to limit the joint movement or to accommodate the joint movement so that the damages caused by excessive relative displacements could be mitigated. To select and design appropriate devices to mitigate the relative displacement-induced damages to bridge structures during earthquake shaking, it is important that results from the previous studies are well understood. This paper presents an overview on various pounding and unseating mitigation devices that have been proposed by various researchers. Based on an extensive review of up-to-date literatures, the merits and limitations of these devices are discussed.     

屈曲约束钢板剪力墙约束板研究(II)——承载力需求及试验验证

本文基于薄板大挠度理论,推导了钢板剪力墙所受剪力与面外挠度的关系,并考虑了弹 塑性屈曲的影响,得到了屈曲约束钢板剪力墙达到极限承载力时的面外挠度,将其代入平衡偏 微分方程后得到了芯板与约束板间面荷载的计算公式。根据国内相关规范,提出了约束板的整 体抗弯、冲切、局压等承载力验算方法,并最终得到约束板的承载力需求公式。此外,本文还 给出了芯板与约束板间连接螺栓的设计公式。最后,本文通过试验对屈曲约束钢板剪力墙约束 板的设计要求进行了验证。     

钢板剪力墙抗震行为与设计

本研究主要目的在于针对未束制型钢板剪力墙的使用性与消能特性加以改良,并研发束制型钢板剪力墙试体,共规划四座试体,3cm厚之低降伏LYS钢板为墙体:一座完全不加束制构件,另两座试体分别在LYS钢板墙体之两面以矩型钢管束制之,第四座则以钢筋混凝土板(简称为CP板)束制LYS钢板墙,于地震工程研究中心进行试验,同时并研究钢板剪力墙的分析模型,包括精准的Strip Model供研究者应用,与较简易的等效斜撑模型供工程实务应用。试验结果显示,束制型钢板剪力墙,LYS钢板挫屈所产生之声响减小,且平面外侧向挫屈变形也随之减少,而消能效果也明显增加。束制与未束制钢板剪力墙之分析模型采用Strip Model,皆可以准确仿真出试验所得之迟滞循环。在单向侧推分析中,采用等效层斜撑模型仿真束制型钢板剪力墙的初始劲度以及强度与试验结果接近。     

中小跨径板式橡胶支座梁桥横向抗震设计研究

为提高中小跨径板式橡胶支座梁桥在强震作用下的横向抗震性能,在总结汶川震区该类梁桥震害特点和国内外桥梁抗震设计规范中相关抗震设计策略规定的基础上,归纳当前我国板式橡胶支座梁桥横向抗震体系存在的问题,提出适合我国中小跨径板式橡胶支座梁桥的横向抗震设计方法,即允许上、下部结构连接构件牺牲的准隔震设计方法,介绍该抗震设计方法设计思想,给出在两设防水准下结构各部件的性能目标要求。选择一座典型板式橡胶支座简支梁桥为研究对象,基于文中抗震设计方法的设计思想,提出采用新型隔震系统对计算桥例进行准隔震设计。结果表明：通过对横向限位装置力学性能参数的合理设计,通过桥梁结构在强震作用下板式橡胶支座的滑移、横向限位装置的损伤或牺牲,控制上、下部结构间传递的梁体惯性力,保护墩柱和基础等下部结构免遭严重损害,同时能有效控制墩梁相对位移,防止过大的梁体移位导致的交通阻断、甚至落梁。     

梁式桥防止地震碰撞及落梁装置与措施的研究进展

在强烈地震中,桥梁上部结构在伸缩缝处发生的碰撞能够引起上部结构的破坏,并影响到支座、墩身和基底的受力状态,在地震作用下的落梁现象也多有发生。本文综述了国内外在避免地震时桥梁之间的碰撞及防止落梁措施方面的研究进展,并且介绍了几种纵向连接装置的性能。对进一步研究提出了新的思路。     

Seismic response control of high arch dams including contraction joint using nonlinear super-elastic SMA damper

In this study, the shape memory alloy (SMA) restrainer bars utilized to reduce the seismic response of arch dams with vertical contraction joints were investigated. The SMA damper model and the nonlinear behavior of arch dams affected by contraction joint opening/closing during earthquakes were simulated in ANSYS. Moreover, the nonlinear damping control principle and method were discussed. The effectivity of the SMA restrainer bars in arch dams was assessed through comparing with a traditional measure of reinforced steel across contraction joints. The SMA restrainer bars were effective in limiting the relative openings of the contraction joints and reducing the seismic acceleration. In addition, the new SMA vibration damper devices of arch dams are simple and easy to install.