A Review of the Key Points in the Design of Small-Radius Curved Ramp Bridges

This article explores the fundamentals of small-radius curved ramp bridges.It covers the selection of box girder spans,support methods,and forms,along with design optimization techniques for this type of bridge structure.The purpose of this paper is to provide robust support for enhancing the design quality of these bridges and ensuring their efficacy in real-world applications.

Simplified Method and Influence Factors of Vibration Characteristics of Isolated Curved Girder Bridge

The isolated curved girder bridge's vibration characteristics play a major part in the seismic responses of structures and anti-seismic properties.A clear analytic relationship between design parameters and the system's vibration characteristics could be established by its simplified dynamic analysis model,making it convenient for providing a reference to the optimization of design and safety analysis.A double-mass six-degree-of-freedom model for curved girder bridges with isolation bearings installed at the top of the bridge piers is built and a simplified analysis method for the vibration characteristics of the system is provided.Combined with the Matlab programming,the influences of radius of curvature,central angle,bridge deck width and damping ratio of the isolation layer and circular frequency of the isolation layer of isolated curved girder bridges on the pseudo-undamped natural circular frequency(called pseudo-frequency for short)and system damping ratio are systematically analyzed,and the sensitivity of vibration characteristics of isolated curved girder bridges is studied.The results show that the vibration characteristics of isolated curved girder bridges can be reflected well with this simplified model and calculation method.The pseudo-frequency of curved girder and system damping ratios increases with the increase of the isolation layer.The third-order vibration characteristic is more sensitive to the parameters of a curved girder,and the first-order vibration characteristic is sensitive to both central angle and radius of curvature to some extent while insensitive to the width of the bridge deck.Furthermore,the second-order vibration characteristic is not sensitive to the parameters of a curved girder.

Coupled Vibration of Long-Span Railway Curved Girder Bridges and Vehicles

The structure of a long curved girder bridge is represented with a three-dimensional curved finite element model. Each 4-axle ~vehicle is modeled by a dynamic system of 35 degrees of freedom. The random irregularities of the track are generated from a power spectral density function under the given track condition. The dynamic interaction between the bridge and train is realized through the contact forces between the wheels and track. Then based on these models, the coupled equations of motion are solved by applying the time-integration and iteration techniques to the coupled system. The proposed formulation and the associated computer program are then applied to a real curved girder bridge. The dynamic responses of the bridge-vehicle system and the derailments and offload factors related to the riding and running safeties of vehicles are computed. The results show that the formulation presented in this paper can well predict dynamic behaviors of both bridge and train with reasonable computation efforts.

Research review on steel–concrete composite joint of railway hybrid girder cable-stayed bridges

Purpose–This study aims to research the development trend,research status,research results and existing problems of the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge.Design/methodology/approach–Based on the investigation and analysis of the development history,structure form,structural parameters,stress characteristics,shear connector stress state,force transmission mechanism,and fatigue performance,aiming at the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge,the development trend,research status,research results and existing problems are expounded.Findings–The shear-compression composite joint has become the main form in practice,featuring shortened length and simplified structure.The length of composite joints between 1.5 and 3.0 m has no significant effect on the stress and force transmission laws of the main girder.The reasonable thickness of the bearing plate is 40–70 mm.The calculation theory and simplified calculation formula of the overall bearing capacity,the nonuniformity and distribution laws of the shear connector,the force transferring ratio of steel and concrete components,the fatigue failure mechanism and structural parameters effects are the focus of the research study.Originality/value–This study puts forward some suggestions and prospects for the structural design and theoretical research of the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge.

不同地震激励方向下隔震曲线梁桥易损性分析

为进一步评估隔震曲线梁桥在地震激励下的抗震性能,从地震易损性角度出发并兼顾考虑地震激励方向对其易损性的影响。利用APDL建立采用板式橡胶支座的隔震曲线梁桥有限元模型,从PEER中选取同一地震事件中的近断层地震动,按规范规定比例输入水平双向地震动进行非线性动力时程分析,结合地震响应与损伤指标计算得到各构件地震易损性曲线;考虑地震激励方向的变化,通过MATLAB编程绘制得到桥梁结构构件(桥墩与支座)以及整体系统的地震易损性曲面,分析探讨地震激励方向对隔震曲线梁桥易损性的影响。结果表明:不同极限状态下各桥墩切向损伤条件概率明显大于其径向,各支座的切向与径向易损性相差不大,但仍是各支座的切向易损性略大于径向易损性;桥梁各构件(桥墩与支座)切向易损性对地震激励方向均表现出很强依赖性,而径向易损性对其的依赖性相对较弱,且伴随损伤等级的提高,构件易损性对地震激励方向更加敏感;桥梁整体系统易损性对地震激励方向的变化不太敏感,且因各构件响应之间的相关性较高,其系统易损性更接近于易损性最大的构件——易损性下限;当进行隔震曲线梁桥抗震性能评估时,应考虑不同地震激励方向对其地震易损性的影响,从而使得易损性分析结果更加合理,能够更加真实地反映隔震曲线梁桥的实际损伤状态。

Field validation of UHPC layer in negative moment region of steel-concrete composite continuous girder bridge

Improving the cracking resistance of steel-normal concrete(NC)composite beams in the negative moment region is one of the main tasks in designing continuous composite beam(CCB)bridges due to the low tensile strength of the NC deck at pier supports.This study proposed an innovative structural configuration for the negative bending moment region in a steel-concrete CCB bridge with the aid of ultrahigh performance concrete(UHPC)layer.In order to investigate the feasibility and effectiveness of this new UHPC jointed structure in the negative bending moment region,field load testing was conducted on a newly built full-scale bridge.The newly designed structural configuration was described in detail regarding the structural characteristics(cracking resistance,economy,durability,and constructability).In the field investigation,strains on the surface of the concrete bridge deck,rebar,and steel beam in the negative bending moment region,as well as mid-span deflection,were measured under different load cases.Also,a finite element model for the four-span superstructure of the full-scale bridge was established and validated by the field test results.The simulated results in terms of strains and mid-span deflection showed moderate consistency with the test results.This field test and the finite element model results demonstrated that the new configuration with the UHPC layer provided an effective alternative for the negative bending moment region of the composite beam.

振动标线设置对连续梁桥的挠度冲击系数影响研究

为了研究振动标线设置对长大坡桥梁结构挠度冲击系数的影响,以30 m连续箱梁桥和五轴车辆为研究对象,基于实际振动标线结构形式进行不平顺度模拟,建立车桥耦合振动方程。借助ANSYS及APDL语言,采用直接积分法进行求解,得到了不同跨中位置挠度时程曲线和冲击系数,研究了振动标线数量、组间距和位置对连续梁桥不同跨中截面挠度冲击系数的影响。结果表明,设置振动标线后连续梁桥挠度冲击系数均大于规范值,且最大值为规范值的2.40倍;振动标线组数增加对下坡方向第一跨跨中位置挠度冲击系数影响不大,但对第二跨跨中挠度冲击系数有较大影响;随着振动标线组组间距增大,不同跨中截面挠度冲击系数变化规律不同;振动标线设置位置对不同跨中截面挠度冲击系数有一定影响;当振动标线组数为6时,首条振动标线宜选择距梁端距离4 m位置,振动标线组间距宜为4.5 m,当振动标线组数为4或5时,需根据不同跨径布置选择相应的振动标线设置形式。研究结论可为桥梁结构中振动标线的设置提供参考。

中低速磁浮圆曲线钢箱梁桥车致振动响应研究

随着圆曲线钢箱梁桥在城市交通中的应用愈发广泛,为探究其在中低速磁浮车辆运行作用下的振动响应特性,基于多体动力学和有限元方法建立车辆-轨道-钢箱梁刚柔耦合动力学模型,采用动态电磁阻尼力影响的二维磁轨关系,并考虑轨道关键部件的参振作用,分析圆曲线段钢箱梁的振动特性,探讨钢箱梁板厚、车辆速度及车体质量对钢箱梁振动响应的影响。结果表明:受曲率影响,钢箱梁在发生弯曲的同时亦会伴生扭转,产生弯扭耦合振动;钢箱梁的振动主要由10~20 Hz的钢箱梁整体弯曲振动、30~40 Hz的钢箱梁扭转振动以及50~70 Hz的轨道局部振动引起;计算得到的钢箱梁跨中横向及垂向最大挠度分别为1.26 mm、3.88 mm,均满足相关标准要求,钢箱梁具有足够的支撑刚度;各工况下的垂向加速度均未超过5.0 m/s^(2)的限值,且最高达到2.2 m/s^(2);在板厚10 mm以及超员载荷工况下,横向加速度大多超过1.4 m/s^(2)的限值,且最高达到4.0 m/s^(2);车辆速度的减小和车体质量的增加均会放大弯扭耦合作用影响,而板厚的增加则能够有效降低弯扭耦合作用影响,当板厚由10 mm增至40 mm时,一阶横弯及扭转频率对应振幅分别减小94.3%、98.7%。

不同桥墩布置形式下有轨电车小半径曲线桥地震响应研究

为适应现代交通的发展需要,有轨电车小半径曲线桥得到广泛应用。而由于曲线桥的几何非规则性,其地震响应相较其余桥型更为强烈和复杂,如何在设计时尽可能减小曲线桥震害值得深入研究。以某实际工程项目为背景,分别建立不同桥墩墩高布置形式的三维有限元模型,通过非线性动力时程分析,探究了等高型、渐变型、凹岛型以及凸岛型等布置形式下各个桥墩的内力响应与位移响应,并为曲线桥的抗震设计提出建议。通过对比与分析表明:有轨电车小半径曲线桥在抗震设计中应优选等高型布置形式,尽量避开渐变型,且在实际工程中需注意对固定墩采取必要的抗震构造措施。

基于墩柱增设的独柱墩曲线箱梁桥抗倾覆研究

近年来,独柱墩曲线箱梁桥整体侧翻倾覆事故时有发生,开展抗倾覆分析及加固对策的研究具有重要的工程价值。以某匝道桥为工程背景,考虑其抗倾覆稳定性,使用支座失效法并结合有限元分析软件Midas/Civil建立柔性梁格有限元模型,对独柱墩曲线箱梁桥加固前后的抗倾覆稳定性和动力特性进行了对比分析。研究结果表明:加固前该桥曲线箱梁的一阶振型为扭转振动,在4号墩处,易发生扭转,可能导致支座脱空,此时该桥抗倾覆稳定系数最小为1.97,不满足规范中抗倾覆稳定系数不小于2.50的要求。采用墩柱增设法对4号墩进行加固后,该桥曲线箱梁的一阶振型为纵向弯曲振动,抗倾覆稳定系数最小为4.31,抗倾覆能力得到显著提升。通过现场抗倾覆稳定性静载试验,对加固效果进行了实桥验证,效果较好。

曲线钢-混组合箱梁桥车桥耦合振动及支座受力研究

曲线钢-混组合箱梁桥已经建设较多,在设计中因对其车桥耦合振动认识有限,相关支座反力因弯扭耦合效应引起的变化情况等尚未很好解决。基于ABAQUS有限元软件,利用傅里叶级数描述车辆平、竖曲线运动,实现了曲线梁桥车桥耦合振动的数值分析,并基于既有试验和理论成果验证了方法的准确性。以某4跨曲线钢-混组合箱梁桥为例,分析了车辆在内、外侧车道以不同速度行驶及超高条件下对桥梁支座反力的影响。结果表明:当车辆沿着曲线梁桥内侧或外侧车道行驶时,另一侧箱梁的外支座会出现脱空的现象。车速对支座峰值反力的影响较小,但可以通过较低的车速减轻支座脱空。超高对支座反力的影响较小,车辆沿着内侧车道行驶时,缓解了外侧箱梁部分支座脱空;沿着外侧车道行驶时,加重了内侧箱梁支座脱空。

上横高速公路小曲线半径钢箱梁桥线形控制技术研究

随着我国高速公路建设的快速发展,小曲线半径钢箱梁桥的应用愈发广泛,但其线形精度更加难以控制.本文以广西上横高速公路工程为工程背景,首先研究了影响小曲线半径钢箱梁线形控制的关键因素,进而提出了相应改进措施.研究结果表明:发现安装位置与高程偏差、焊接作用影响与温度变化影响是线形控制的关键因素.温差增加10℃时,钢箱梁最大线形误差增加近20.8 mm;当拼装顺序为最优时,最大线形误差可减少14.1%.通过施工前数值模拟确定最优拼装顺序提升线形控制精度,钢箱梁焊接时在对接部位中心处开始焊接控制横向及竖向变形等改善措施的应用,显著提升了线形平顺度合格率,取得了良好的经济效益.

弯曲桥梁抗倾覆性能分析与加固设计

抗倾覆性能是曲线桥梁的一项重要安全性指标。对于某高速公路工程平面弯曲梁桥,通过空间有限元建模分析,计算了弯曲混凝土连续箱梁的抗倾覆稳定系数与支座反力,并进行了抗倾覆加固设计。由分析验算结果可知,钢板混凝土盖梁加固措施受力简明、施工方便,宜用于快捷加固独柱墩弯曲桥梁以增强其抗倾覆性能。

小曲率半径钢混组合梁预制叠合与架设施工技术

本文针对海域互通匝道小曲率半径钢混组合梁桥架桥机架设施工难题,从钢混组合梁预制叠合施工工艺与线形控制、大横坡运梁设备改造与运梁技术、小曲率半径架桥机设计与架设工艺等方面展开研究,并对关键施工工况进行了模拟计算,系统研究了小曲率半径钢混组合梁桥后场叠合与架桥机架设施工技术,保障了杭甬高速公路复线滨海枢纽工程施工的顺利实施,也为后续小曲率半径梁桥架设提供了参考经验。

曲线主梁异形拱肋桥梁结构体系设计及受力分析

景詹沙河大桥位于江苏省溧阳市天目湖景区,全长248 m,跨径布置80 m+123 m+45 m。大桥采用异形拱曲梁协作结构体系,曲线梁、异形拱和扇形空间索面共同形成古琴造型,整体造型简洁新颖,突破了传统拱桥外形。文章阐述了大桥主体结构设计,结合有限元计算模型,对结构体系进行比选,最终确定采用拱墩分离的结构体系。经验算,结构安全满足设计要求,可为类似桥梁的设计与施工提供借鉴和参考。

支座类型对曲线梁桥抗震性能的影响分析

曲线梁桥在高等级公路及城市高架桥中应用广泛,但与直线梁桥相比,曲线梁桥在遭遇地震时更容易产生损坏、垮塌等严重后果。支座在曲线梁桥抗震中起着重要的作用。以潍坊至青岛高速公路景芝互通A匝道桥为依托,通过有限元分析计算板式橡胶支座、盆式支座和铅芯橡胶支座等不同支座类型对曲线梁桥抗震性能的影响,结果表明:铅芯橡胶支座的减隔震效果最好,板式橡胶支座在提高下部结构抗震安全性方面表现较好,但支座变形过大容易引起上部梁体滑移,与上部限位措施配套使用效果更好。

高速匝道钢箱梁桥步履顶推施工研究

增设新出入口作为城区段高速网络改扩建扩容的一种方式,新增匝道需跨既有线路修建。在“保通高效”的要求下,匝道钢箱梁步履顶推作业具有施工占地少、基建土方施工少、曲直通适、施工速度快、无需封闭现有交通的特点在工程中得到广泛应用。其施工原理是通过钢箱梁及导梁节段预拼,以分布于钢箱梁底的顶推设备,通过系统控制设备同步运行将结构推送至预定位置落梁成桥。本文主要就高速匝道钢箱梁步履顶推施工技术进行了分析。