整体式无缝桥梁桥台高度对主梁受力性能研究

利用大型有限元软件ABAQUS,建立了整体式无缝桥梁全桥与台后土体及桩周土体相互作用的三维非线性有限元计算模型,分析了在砂类土地基中,不同桥台高度在自重及温度荷载作用下对整体式无缝桥梁主梁的受力影响,得出了一些有益的结论。     

整体式无缝桥梁非线性有限元计算模型研究

以已建整体式无缝桥梁为例,利用大型有限元软件ABAQUS,采用理想线弹性模型,模拟桥梁主体结构,并在考虑地基初始地应力平衡下,建立了整体式无缝桥梁与台后土体及桩周土体相互作用的三维非线性有限元计算模型,分析在自重及温度荷载作用下整体式无缝桥梁的受力情况,通过与实桥的应力实测值和其他不同方法进行对比分析,从而验证所提出计算模型的可行性。     

基于滑坡破坏模式的桥台位移耦合计算

地震作用下桥台永久变形大小是评价桥梁基础地震稳定性的一个重要指标。首先分析地震下桥台破坏特点,提出简化桥台滑坡破坏模式,在此基础上考虑土体强度衰减效应对桥台稳定性的影响,将桥台-土体地震动力响应分析与Newmark有限滑移计算方法相耦合,提出桥台滑移计算公式。然后将计算结果与R-E方法进行对比,结果表明:提出的计算模型能较好地反映桥台-土体的破坏特点,较充分地考虑地基土软化对桥台的稳定作用,以及在一定程度上考虑桥台-土体的地震动力响应特性;土体强度衰减对桥台-滑坡体的稳定性影响很大,在计算中不可忽视。     

水平荷载作用下整体式桥台桥梁受力性能研究

整体式桥台桥梁近些年在国内外出现的越来越频繁,相比于传统的桥梁结构,其在提高桥梁的耐久性等方面发挥着极大的优势作用。以实际工程为背景和试验对象,对整体式桥台桥梁的受力性能进行了分析和研究,并通过与桩内应力试验实测值进行分析,得出在制动力的作用下,单侧桥台的受力相似于均匀温差下的受力。结果表明,P-y曲线法在分析整体式桥台桥梁水平荷载下的受力性能方面具有较好的可行性。     

温度作用下整体式桥台曲线梁桥受力特征分析

为探究整体式桥台曲线梁桥在温度作用下的受力特征,文章通过对既有曲线梁桥进行试设计,考虑土-结构相互作用,建立有限元模型并进行参数化分析。研究表明,温度作用对整体式桥台曲线梁桥的内力和变形影响显著,尤其对边跨的内力分布影响较大;曲率半径是温度变化条件下影响整体式桥台曲线梁桥梁端弯矩和径向位移的重要因素;合理选择台后填土类型,以改善主梁切向变形和梁端内力大小。     

软土地区整体式无缝桥梁数值模拟和荷载试验对比分析

由于整体式无缝桥梁在桥墩、桥台处刚接,计算活载效应相对较复杂。结合滨海软土地基区域的工程实例,进行三维有限元数值模拟和静动试验对比分析,从中了解整体式桥梁在活载作用下的位移、应力以及动力特性,为类似中心跨径的整体式桥梁提供参考。     

整体式桥台无缝桥梁技术

整体式桥台无缝桥梁是将桥梁的上部结构与桥台结为整体,避免了伸缩缝桥梁常见的水侵蚀和冻害。分析了桥梁伸缩缝装置存在的问题;介绍了国内外无伸缩缝桥梁的工程实践;提出了整体式桥台无缝桥梁应用中存在的问题。     

单跨整体式桥台钢混组合梁桥设计研究

以福州某桥梁工程为例,介绍了桥梁在景观、快速建造等要求下,桥梁的总体几何布置、主梁与桥台的结构选型以及尺寸拟定,并应用有限元分析软件MIDAS CIVIL建立了空间梁格模型,分析了单跨整体式桥台钢混组合梁桥在施工阶段和使用阶段的受力情况,论证了单跨整体式桥台钢混组合梁桥设计的可行性和合理性。     

整体式桥台桥梁极限长度

以目前世界上最长的整体式桥台桥梁Isola della Scala桥为实例建立有限元模型,通过实桥动力测试对模型进行校正;提出整体式桥台桥梁极限长度的简化计算公式,并通过有限元模型验证其精确性;利用该简化计算公式预测不同限制条件下整体式桥台桥梁的极限长度。结果表明:考虑桥墩的转动能力和桥台的承载能力时,极限长度可以达到540m;考虑温度位移产生的疲劳影响时,极限长度可以达到450m;考虑桥头搭板的耐久性时,极限长度可以达到430m。     

考虑土、上部结构和桥台相互作用的桥台抗震性能研究

 在以往的桥梁设计中并不考虑基础提离和地基土屈服等土与桥台相互作用对桥台地震反应的影响。因此,为了研究桥台在地震中的抗震性能,采用Newmark时程分析方法对考虑土、上部结构和桥台相互作用的由扩展基础支撑的桥台进行分析。采用离散的质点–弹簧模型对土、上部结构和桥台系统进行建模。利用非线性模型,模拟上部结构和桥台的碰撞反应、桥台背部填土及地基土的弹塑性反应,并采用Winkler地基梁模型模拟地基土与桥台基础的相互作用。分析结果表明,桥台基础的提离作用可以减弱桥梁上部结构及桥台在强烈地震中的反应,减小桥台墙身底部在强震作用下发生的塑性变形,起到一定的减震隔震效果。同时,桥台底部土的屈服减小了传递到桥台底部塑性铰处的弯矩,进一步增强了桥台基础提离的效果。然而,由地基土屈服引起的永久性沉降也造成桥台基础的倾斜。因此,在桥梁的抗震设计中,必须考虑桥台基础的提离和地基土的屈服等土与结构相互作用对桥台抗震性能的影响。     

索、塔参数对三跨部分斜拉桥动力特性的影响分析

以国内首座公路三跨预应力混凝土部分斜拉桥为背景,建立基准有限元动力计算模型,通过参数敏感性分析,研究索、塔构件对该桥梁体系结构动力特性的影响规律。引入动力影响度概念,量化分析索、塔参数对三跨部分斜拉桥动力特性的影响程度。     

大跨度斜拉管线桥的动力特性分析

本文结合一实际工程结构－－斜拉管线桥,从动力分析模型的建立、计算结果与实测结果的比较以及与普通斜拉桥的比较等几个方面研究了这种新型结构的动力特性。结果表明：恒载初始内力对斜拉管线桥的动力特性影响很大;尽管与斜拉桥结构相似,但二者的动力特性却有很大差别。     

独柱塔空间缆索自锚式悬索桥动力特性分析

为研究独柱塔空间缆索自锚式悬索桥的动力特性,以南京江心洲大桥为工程背景,运用有限元软件Midas/civil 2015,分别建立了成桥状态的墩底固结模型和桩-土相互作用模型,对比分析了桩-土相互作用对结构动力特性的影响,并分析了恒载集度、加劲梁刚度、桥塔刚度、主缆刚度以及吊杆刚度对该类桥梁动力特性的影响规律。分析结果表明,考虑桩-土相互作用时,结构自振周期延长了1.4s,并且振型发生了变化;恒载集度主要影响结构竖弯振型;加劲梁竖向刚度对结构竖弯振型影响较大;加劲梁扭转刚度对结构各主要振型影响均不明显;桥塔纵向刚度主要影响结构纵飘振型;桥塔横向刚度对桥塔横弯振型影响较大;主缆抗拉刚度主要影响加劲梁竖弯振型;吊杆抗拉刚度的提高对结构整体刚度的贡献可以忽略。     

Seismic assessment of masonry arch bridges

In this paper, the seismic performance of existing masonry arch bridges is evaluated by using nonlinear static analysis, as suggested by several modern standards such as UNI ENV 1998-1 2003, OPCM 3274 2004, and FEMA 440 2005. The use of inelastic pushover analysis and response spectrum approaches becomes more difficult when structures other than the framed ones are investigated. This paper delves into the application of this methodology to masonry arch bridges by presenting two particular case studies. The need for experimental tests in order to calibrate the materials and the dynamic properties of the bridge is highlighted, in order to correctly model the most critical regions of the structure. The choice of the control node in the pushover analysis of masonry arch bridges and its influence on seismic safety evaluation is investigated. The ensuing discussion emphasizes important results, such as the unsuitability of the typical top node of the structure for describing the bridge seismic capacity. Finally, the seismic safety of the two bridges under consideration is verified by presenting an in-depth vulnerability analysis.     

某双曲拱桥的动静力测试及承载能力评估

本文以某双曲拱桥的承载力评估为例,在总结几种有限元模型离散方法的基础上,结合双曲拱桥的结构形式,提出采用梁板结合的模拟方法,用大型通用有限元软件ANSYS进行了双曲拱桥的模型建立.同时,阐述了双曲拱桥的动载及静载试验的试验方法与过程,包括用等代荷载的方法确定荷载车辆、各种工况的分级加载、动载及静载试验测点的布置.依据有限元分析结果与动静力荷载结果的对比分析,对工程实例桥的承载能力进行了评估分析,得出了该桥当前的结构性能和状况.结果表明,正确的计算模型是评定双曲拱桥承载能力的关键,有限元法中的板梁法结合双曲拱桥的结构形式,是双曲拱桥结构空间分析的一种有效方法,以有限元理论分析和动静力荷载试验相结合的方法能较为全面地评定双曲拱桥的承载能力,可为同类桥梁计算分析及承载能力评定提供参考.     

Vibration of railway bridges under a moving train by using bridge-track-vehicle element

During the last two decades, much attention has been paid to various vibration problems associated with railways. They include the dynamic response of railway bridges and railway tracks at grade under the action of moving trains. However, studies on the role of track structures on the vibration of railway bridges are rather limited. In this paper, a new element called bridge-track-vehicle element is proposed for investigating the interactions among a moving train, and its supporting railway track structure and bridge structure. The moving train is modelled as a series of two-degree-of-freedom mass-spring-damper systems at the axle locations. A bridge-track-vehicle element consists of vehicles modelled as mass-spring-damper systems, an upper beam element to model the rails and a lower beam element to model the bridge deck. The two beam elements are interconnected by a series of springs and dampers to model the rail bed. The investigation shows that the effect of track structure on the dynamic response of bridge structure is insignificant. However, the effect of the bridge structure on the dynamic response of the track structure is considerable.     

Effectiveness of Soil–Structure Interaction and Dynamic Characteristics on Cable-Stayed Bridges Subjected to Multiple Support Excitation

The purpose of the study is to determine the effects of multiple support excitations (MSE) and soil–structure interaction (SSI) on the dynamic characteristics of cable-stayed bridges founded on pile foundation groups. In the design of these structures, it is important to consider the effects of spatial variability of earthquake ground motions. To do this, the time histories of the ground motions are generated based on the spatially varying ground motion components of incoherence, wave-passage, and site-response. The effects of SSI on the response of a bridge subjected to the MSE are numerically illustrated using a three-dimensional model of Quincy Bayview cable-stayed bridge in the USA. The soil around the pile is linearly elastic, homogeneous isotropic half space represented by dynamic impedance functions based on the Winkler model of soil reaction. Structural responses obtained from the dynamic analysis of the bridge system show the importance of the SSI and the MSE effects on the dynamic responses of cable-stayed bridges.     

Nonlinear Computer Model for the Simulation of Lock-in Vibration on Long-Span Bridges

Abstract:   The susceptibility of modern bridges to vortex-shedding-induced vibration is a major concern for researchers and designers. The relevance of this phenomenon is associated with the onset of large-amplitude aeroelastic vibration at moderate wind-velocity regimes due to synchronization, that is, lock-in, of the vortex-shedding frequencies with those corresponding to the natural modes of the structure. Recent observations, either recorded during the monitoring of full-scale bridges or during experimental tests of deck models in wind tunnels, confirm the importance of these aspects during the operational life of the structure. In this article, a computer model for the simulation of the aeroelastic loading associated with vortex shedding in lock-in regime is presented, for a direct application to dynamic analysis of long-span bridges. This approach is based on earlier work focused on the response of slender vertical cylindrical chimneys to vortex-shedding excitation, which is here extended to noncircular cross sections. The numerical model was employed in conjunction with a finite-element code for time-domain nonlinear simulation of the structural dynamic response. The validation of the procedure is performed through numerical simulation, conducted on two specific bridge examples.     

钢管混凝土组合格构柱高墩大跨连续刚构桥动力特性分析

结合某山区高墩大跨连续刚构桥的动力特性分析,研究了钢—混凝土组合格构柱高墩连续刚构桥的动力特性分析方法,探讨了该类桥梁的动力特性结构行为及规律;在一定参数的基础上,研究了墩高、边界约束条件、曲线形式、曲线半径和横向连接系等参数的影响。计算结果为该类桥梁的抗风、抗震设计研究提供了分析基础。     

斜拉桥单、双主梁建模动力特性比较

为研究不同建模方法对斜拉桥动力特性的影响,首先以简支梁为研究对象进行分析。文中分别采用单主梁、双主梁对简支梁和斜拉桥进行建模并进行动力特性计算,对两种建模方法计算的结果进行对比,分析两种建模方法对计算桥梁动力特性产生差异的原因。计算结果表明,两种建模方法对竖向弯曲频率、扭转频率影响较小,对横向弯曲频率影响较大。