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.

Preliminary Estimation of Torsion of Curved Bridges Subjected to Earthquake Loading

This paper focuses on the seismic response of the curved and post-tensioned concrete box girder bridges. More specifically, it investigates how the curvature influences the response of a bridge subjected to earthquake. Parametric analysis of different radius of curvature is performed and the internal forces, torsion moment, axial and shear along the bridge are calculated. Two types of connections are investigated, the monolithic connection and deck connection with bents and abutments with rubber bearing. The response spectrum seismic analysis was performed. The models were designed, according to the provisions of EC8-part 2, EC2 and the Greek regulations E39/99. Diagrams relating the curvature with the torsion moment have been obtained from the results of parametric analysis. These diagrams could be used by engineers for preliminary design of such kind of bridges.

Identification of Connection Flexibility Effects Based on Load Testing of a Steel-Concrete Bridge

In the case of composite girders, an effective cooperation of both parts of the section is influenced by deformability of connectors. Limited flexural stiffness of welded studs, used commonly in bridge structures, does not provide full interaction of a steel beam and a concrete slab. This changes strain distribution in cross-sections of a composite girder and results in redistribution of internal forces in steel and concrete element. In the paper partial interaction index defined on the basis of a neutral axis position, which can be used for verification of steel-concrete interaction in real bridge structures rather than in specimens is proposed. The range of the index value changes, obtained during load testing of a typical steel-concrete composite beam bridge, is presented. The investigation was carried out on a motorway viaduct, consisting of two parallel structures. During the testing values of strains in girders under static and quasi-static loads were measured. The readings from the gauges were used to determine the index, characterizing composite action of the girders. Results of bridge testing under movable load, changing position along the bridge span is presented and obtained in-situ influence functions of strains and index values are commented in the paper.

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.

Study on the Mechanical Properties of Irregular Curved Steel Box Girder for City Viaduct

This paper deeply analyses the influence of different local tectonic on stress performance of spatial curved steel box Girder Bridge, using the finite element analysis software to establish space finite element model of this bridge, calculation and analysis were made on the bridge of the strength, stiffness. It has certain reference value for guiding engineering design, have a good foundation for the mechanical properties and stability of linear and nonlinear further study of curved steel box girder.

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.

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。

考虑变墩高效应的小半径曲线梁桥地震易损性研究

为分析墩高变化形式对小半径曲线梁桥地震易损性的影响,以某互通式立交匝道桥第2联为背景,设计渐变型、凹岛型、凸岛型3种墩高变化形式曲线梁桥进行地震易损性研究。在提出的压弯剪扭耦合作用破坏的基础上,采用集中铰-纤维模型的桥墩建模方法,通过SeismoStruct有限元软件建立3种墩高变化形式曲线梁桥模型;选取符合Ⅲ类场地特性的50条地震波,利用能力需求比法,以位移延性比为损伤指标,研究不同变墩高形式下桥墩与支座的地震易损性。结果表明:当小半径曲线梁桥采用3种墩高变化形式时,以弯曲受力为主的中、高墩在地震作用下发生完全破坏概率较低,以弯剪或剪切受力为主的矮墩在强震作用下发生完全破坏概率较大,变墩高曲线梁桥可以适当提高矮墩的抗震能力;凹岛型墩高变化形式会增加矮墩的损伤概率,在抗震设计中应避免选择该墩高变化形式或尽可能优化墩梁连接方式;墩高变化形式对于支座的易损性影响小于对桥墩的影响。

有轨电车小半径曲线梁桥减隔震措施对比研究

为适应交通路网发展需求,小半径曲线桥被广泛应用,其中有轨电车小半径曲线桥占据较高的比重。为确保地震区有轨电车的抗震安全,常采用减隔震装置以减小地震响应。然而,不同装置类型和布置方式对减隔震效果存在较大差异,因此有必要深入研究优化策略。本文以某典型有轨电车小半径曲线桥为工程背景,基于多个单一减震装置有机组合,依据边墩控制位移、中墩降低内力的组合减震理念,提出了一种新型的组合减隔震装置,并选择适宜参数的摩擦摆支座(FPS)、铅芯橡胶支座(LRB)和液体黏滞阻尼器(FVD)三种减隔震装置,通过动力非线性时程分析,探究了各装置关键参数对于曲线桥减震效果的影响,并对采用不同减隔震装置的有轨电车小半径曲线桥地震响应进行对比分析。研究发现:本文提出的组合减隔震方案能够明显弥补单一减隔震装置的不足,达到更好的减隔震效果,值得在同类桥梁中推广应用;FPS与LRB对墩底内力控制效果较好,但会在一定程度上放大结构的墩梁相对位移;FVD对墩梁相对位移的控制效果更好,但对墩底内力的控制效果比其他两种减隔震装置差。

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%。

衢州西站综合交通枢纽项目结构设计

杭衢高铁衢州西站综合交通枢纽及配套项目由综合交通枢纽、站前广场及匝道组成。为解决工程中大跨度拱形钢箱梁、单层网壳+钢网格筒柱、双曲面混凝土屋面以及钢箱梁弯桥等设计重难点问题,设计中对拱形钢箱梁、拉杆拱弧形屋面、钢箱梁弯桥进行结构分析,并对单层网壳+钢网格筒柱进行整体结构缩尺试验及整体结构有限元分析,同时对重要的圆管节点进行足尺试验和有限元分析。结果表明:拱形钢箱梁结构整体刚度好,设计合理;拉杆拱结构自平衡可有效减小基础推力和基础尺寸;单箱双室钢箱梁弯桥强度、刚度、抗倾覆验算均满足设计要求;单层网壳+网格筒柱整体结构在2.0倍标准组合荷载下仍能保持弹性受力状态;通过节点试验和节点有限元分析,验证了大跨度自由曲面钢结构圆管焊接节点的力学可靠性。

两跨独柱墩曲线连续钢箱梁抗倾覆设计方法

独柱墩曲线连续钢箱梁是城市立交匝道桥常用的结构形式,但因其存在支座间距小、内外侧支座支反力差别大、边墩支反力小以及钢箱梁自重轻等诸多缺点,所以抗倾覆性能差便成为此类桥型普遍存在的问题。近年来发生的数十起该类型的桥梁倾覆事故,造成了严重的社会影响及经济损失。依据相关规范中关于桥梁上部结构抗倾覆计算方法,以实际工程为例,对两跨独柱墩曲线连续钢箱梁抗倾覆性能进行计算分析,得出采用双支座并且给主梁边墩位置处配重的方法,并从特征状态1及特征状态2两方面给出了提高该类型桥梁的横桥向抗倾覆性能的设计方法。

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。

受空间约束时曲线钢箱梁步履式多点顶推策略

针对曲线钢箱梁多点步履式顶推同步控制难度高、往往受到各类空间约束限制的难题,为提高顶推施工的精确性与可靠性,应充分降低曲线顶推施工过程中的多点异向和异速顶推工况次数,根据尽量使得顶推过程中曲线箱梁各点顶推方向与速度相同这一基本原则,提出了受空间约束时曲线钢箱梁以平移和纠偏为主,旋转与调整为辅的顶推策略和方法,建立了各基本工法对应的顶推数学模型,并将其成功应用于兰州市某非对称曲线斜拉桥的钢箱梁顶推施工。研究结果表明:随曲线钢箱梁顶推行进,理论计算出的梁体尾部偏差值逐渐变大、梁体所需旋转角度逐渐变小,故曲线钢箱梁顶推初期宜多次采用旋转工法减小曲线夹角,后期宜多次采用纠偏工法减小轴线偏差;调整工法可有效减少其余工法的实施次数,其计算流程独立于其他工法,只与当前曲线钢箱梁到达的临时墩所在平面位置有关;曲线钢箱梁即将穿越桥塔等空间障碍物时,梁体与障碍物碰撞风险最大,而随顶推进程的继续,梁体与障碍物碰撞风险会逐步降低;该曲线钢箱梁顶推策略与方法思路明确、可操作性高,可大幅降低对多点步履式顶推系统的要求,提高顶推施工可靠性,适用于市政桥梁的曲线钢箱梁步履式顶推施工。

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。