桥梁中抗震限位装置设计方法的研究

为防止桥梁上部结构在地震中发生落梁破坏,通常在伸缩缝处安装限位装置。在调查影响伸缩缝处相邻梁体相对位移因素的基础上,根据线性化模型提出一种限位装置设计方法。该方法既考虑了相邻桥跨不同向振动的动力特性,又考虑了相邻梁体间碰撞对相对位移的影响。运用替代结构法考虑墩柱的弹塑性,使用考虑碰撞效应的相对位移反应谱考虑碰撞对相对位移的影响。通过参数研究对提出的限位装置设计方法的可靠性进行验证,并通过与已有的限位装置设计方法相比,评估了所提出的限位装置设计方法的限位效果。与已有的设计方法相比,本文提出的限位装置设计方法与非线性时程分析结果的相关性更好。     

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。     

无桥台伸缩缝多联桥跨结构地震碰撞响应研究

针对地震作用下多联长桥结构中伸缩缝处的碰撞破坏,提出一种取消桥台伸缩缝保留两联间桥墩伸缩缝的新型多联桥跨结构。用Kelvin接触单元模拟桥台伸缩缝和桥墩两联间伸缩缝在地震作用下的碰撞效应,构建包括墩柱、主梁、支座和伸缩缝在内的全桥空间动力分析模型。依托某市立交体系中一座独立多联长曲线匝道桥梁工程,建立4个计算模型;分别输入2组地震波的单维和多维8种地震动工况;利用非线性时程分析法,研究各计算模型在多种地震输入工况下桥台伸缩缝和桥墩两联间伸缩缝的碰撞响应差异。结果表明:无桥台伸缩缝多联桥跨结构可以有效消除或减小地震荷载作用下桥跨结构中伸缩缝处的碰撞破坏,是一种十分有利的抗震结构形式。     

带限位多层隔震结构抗震影响参数研究

高烈度地震下隔震层较大水平位移易造成碰撞或上部结构失稳倾覆,限位装置能够降低其倾覆概率。首先,对多自由度隔震结构设置带间隙弹簧限位装置动力学方程进行了讨论;其次,结合某4层隔震框架结构进行了限位方案设计,并针对限位间距(D)、限位刚度(K)取值范围进行了分析;最后,进行罕遇地震下带限位隔震结构数值计算,并结合顶层加速度峰值、层加速度、层位移、层剪力峰值等指标展开抗震性能对比分析。结果显示随着限位间距D减小、限位刚度K增加,限位效果提升但易造成上部结构响应发生突变,对隔震结构响应影响较大。当限位间距D与罕遇地震下隔震层位移Drar比值在[0.38,0.69]、限位刚度K与罕遇工况隔震层刚度Kh比值在(0,1)时限位效果较好,且降低了上部结构响应突变影响。     

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     

高铁隔震桥梁横向限位装置的研究

我国属于地震多发的国家,在地震作用下,隔震桥梁可能发生落梁。基于摩擦摆支座隔震装置,在大震作用下,为减小支座的位移,需要在横桥向加横向限位装置,但因限位装置参与桥梁受力,改变桥墩受力模式。为分析限位装置的作用,采用非线性时程分析方法进行研究,对比得出:加了限位装置能有效地减小墩梁相对位移,但增加了桥墩的地震影响。     

成都博物馆基础隔震结构隔震层抗拉性能设计研究

对不规则结构进行基础隔震时,在地震作用下会在隔震层的局部位置产生较大拉力,橡胶隔震支座易受拉破坏进而影响结构安全性。而采用抗拉限位装置可有效解决隔震层抗拉问题,但相关规范对此未提出相应设计方法及安全性能设计指标。结合已建成的成都博物馆基础隔震工程,通过橡胶隔震支座竖向拉伸及剪拉试验,提出橡胶隔震支座抗拉性能设计指标,并配套开发提升橡胶隔震层抗拉性能的抗拉限位装置,通过对整体结构模型在不同强度地震作用时程分析,提出了该不规则结构基础隔震时隔震层抗拉性能的设计方法及设计指标。研究实现了8度罕遇地震作用时,抗拉限位装置不参与工作或保持弹性工作状态;9度罕遇地震作用时,抗拉限位装置处于不屈服状态,橡胶隔震支座出现塑性,但仍具有很高的拉伸承载能力。     

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。     

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。     

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.     

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.     

地震输入工况对曲线桥梁伸缩缝碰撞响应的影响

针对曲线桥梁伸缩缝地震碰撞破坏现象,结合某多层互通式立交体系中单支多联曲线箱梁桥工程,建立带伸缩缝曲线桥梁的空间动力分析模型。用Kelvin接触单元模拟伸缩缝处地震碰撞效应,建立包含墩柱、主梁、支座和伸缩缝的全桥有限元模型。利用非线性时程分析法,分别输入两组地震波的单维和多维8种地震动工况,分析不同地震工况作用下曲线桥梁伸缩缝的碰撞响应。结果表明:曲线桥梁不同方向地震动响应存在耦合,其伸缩缝碰撞响应的研究应采用多组地震波的单维和多维输入工况分别计算。     

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.     

大跨度双塔悬索桥在地震动行波激励下的响应规律研究

本文以一座主跨850m的大跨双塔悬索桥为工程背景,采用时程分析法研究了行波效应大跨双塔悬索桥地震响应的影响。通过建立三维有限元分析模型,在分析了大跨度双塔地锚式悬索桥动力特性及一致激励下地震响应规律的基础上,进一步探讨了行波效应对大跨双塔地锚式悬索桥地震响应的影响规律。分析结果表明:地震波纵向行波作用下,主塔的地震响应随着视波速的减小而先减小后增大;主梁的竖向振动则较一致激励下显著增大;主缆及吊索轴力则受地震动行波效应的影响不大。     

Seismic behaviour of infilled and pilotis RC frame structures with beam-column joint degradation effect

The influence of the exterior joints capacity deterioration on the local and global failure mechanisms of reinforced concrete structures with infills is investigated. Exterior beam-column joints with reduced capacity is the common case for the majority of RC structures designed according to older design standards. Nevertheless in common practise the response of these regions is typically assumed as rigid. A key parameter of this investigation is the inclusion of the joints strength and stiffness degradation in the study of the seismic performance of the structures. In this direction, a special-purpose rotational spring element that incorporates a special behaviour model is employed for the simulation of the exterior joints’ local response. The spring element has been incorporated in a well-established general program for nonlinear static and dynamic analysis. The effectiveness of the used joint element model has been demonstrated in a previous paper through comparisons with experimental data reported in literature. In this paper an attempt is presented for the investigation of the influence of the exterior joint damage on the seismic behaviour of bare and infilled RC frame structures. Two types of masonry infilled structures are considered: (a) infilled frame and (b) infilled frame without infills at the base storey (pilotis frame). A parametrical study of the overall seismic response using push over analyses and step-by-step analyses is performed. Results in terms of interstorey drifts, base shear, failure mode, ductility requirements and joints rotational requirements demonstrate that neglecting the possible local damage of the exterior joints may lead to erroneous conclusions and unsafe design or seismic behaviour evaluation that subsequently may become critical in some cases. Furthermore the influence of exterior joints degradation has been proven of vital importance for the overall behaviour of pilotis frames.     

Seismic vulnerability assessment of a Californian multi-frame curved concrete box girder viaduct using fragility curves

Seismic response of multi-frame curved viaducts has been proved to be very complex due to typically inherent irregularities identified in this class of bridge structures such as deck in-plane curvature, altitudinal irregularity and deck discontinuity. The discontinuity provided by the expansion joint has made this class of bridges prone to catastrophic damages caused by multiple collisions between adjacent frames during both torsional and translational modes of responses as well as deck unseating at the expansion joints. This paper presents the seismic response of a Californian multi-frame curved concrete box girder viaduct, considering four different radii of curvature and five altitudinal coefficients, using fragility curves. Fragility curves are developed by considering different sources of uncertainties related to earthquakes, structural geometries and material properties. The full nonlinear time-history analyses are performed utilising 3-D numerical bridge models generated in OpenSees finite element platform. The results show that bridge vulnerability increases with increasing irregularity in bridge plan and elevation. It is observed that bridge components and system fragility show different sensitivity to each type and level of irregularity for each damage state. In addition, the obtained results can be used to aid seismic retrofit prioritisation, financial loss estimation, pre-earthquake planning and design improvement processes.     

三跨飞燕式异型钢管混凝土拱桥地震反应及控制

利用ANSYS有限元软件,计算并分析了某三跨飞燕式异型钢管混凝土拱桥的动力特性和一致激励与行波激励下的动力响应,并对拟安装在桥上Lock-up装置的减震效果进行了评价.研究表明,纵向和竖向联合输入下结构的动力反应明显高于纵向和竖向单独输入工况;横向地震激励时,拱肋出平面位移及内力均很大,但可以不考虑行波效应的影响;纵向...     

高墩大跨度连续刚构桥的抗震分析

本文以一座高墩大跨度连续刚构桥的设计实例为背景,建立起动力分析模型,对桥梁结构的动力特性进行了计算分析;并采用线性时程方法,输入实际地震波激励,对该结构在地震作用下的时程响应进行了分析研究,探明了高墩连续刚构桥在纵向、横向和竖向多维地震动作用下的响应特点,为该类结构的抗震设计提供参考。