Dynamic Characteristics of Long -Span Steel -Concrete CompositeBeam Bridge Based on Vehicle -Bridge Coupling Effect

In order to investigate the effect of vehicle-bridge coupling on the dynamic characteristics of the bridge,a steel-concrete composite beam suspension bridge is taken as the research object,and a three-dimensional spatial model of the bridge and a biaxial vehicle model of the vehicle are established,and then a vehicle-bridge coupling vibration system is constructed on the basis of the Nemak-βmethod,and the impact coefficients of each part of the bridge are obtained under different bridge deck unevenness and vehicle speed.The simulation results show that the bridge deck unevenness has the greatest influence on the vibration response of the bridge,and the bridge impact coefficient increases along with the increase in the level of bridge deck unevenness,and the impact coefficient of the main longitudinal girder and the secondary longitudinal girder achieves the maximum value when the level 4 unevenness is 0.328 and 0.314,respectively;when the vehicle speed is increased,the vibration response of the bridge increases and then decreases,and the impact coefficient of the bridge in the middle of the bridge at a speed of 60 km/h achieves the maximum value of 0.192.

Ultimate negative bending-moment capacity of outer-plated steel-concrete continuous composite beams

Static load tests and bearing capacity analyses are carried out for two outer-plated steel-concrete continuous composite beams. The load-deflection curve and the load-strain curve of specimens are obtained and analyzed. The test results indicate that effective cooperation can be achieved by the shearresistant connection between the reinforcement in the negative moment area and the outer-plated steel beam, and the overall working performance of the composite beams is favorable. At the load-bearing limiting state, the plastic strain on the maximum negative and positive moment section becomes fully developed so as to form relatively ideal plastic hinges. With the increase in the reinforcement ratio, the moment-carrying capacity of the composite beams improves significantly, but the ductility of the beams and the rotation ability of the plastic hinges decrease. The formulae for calculating the limit bending capacity in the negative moment area of outer-plated steel-concrete composite beams are proposed based on the test data. The calculated results agree well with the test results.

Double-layer model updating for steel-concrete composite beam cable-stayed bridge based on GPS

In order to establish the relationship between the measured dynamic response and the health status of long-span bridges, a double-layer model updating method for steel-concrete composite beam cable-stayed bridges is proposed. Measured frequencies are selected as the first-layer reference data, and the mass of the bridge deck, the grid density, the modulus of concrete and the ballast on the side span are modified by using a manual tuning technique. Measured global positioning system （GPS） data is selected as the second-layer reference data, and the degradation of the integral structure stiffness EI of the whole bridge is taken into account for the second-layer model updating by using the finite element iteration algorithm. The Nanpu Bridge in Shanghai is taken as a case to verify the applicability of the proposed model updating method. After the first-layer model updating, the standard deviation of modal frequencies is smaller than 7%. After the second-layer model updating, the error of the deflection of the mid-span is smaller than 10%. The integral structure stiffness of the whole bridge decreases about 20%. The research results show a good agreement between the calculated response and the measured response.

Closed-form solution for shear lag effects of steel-concrete composite box beams considering shear deformation and slip

Based on the consideration of longitudinal warp caused by shear lag effects on concrete slabs and bottom plates of steel beams,shear deformation of steel beams and interface slip between steel beams and concrete slabs,the governing differential equations and boundary conditions of the steel-concrete composite box beams under lateral loading were derived using energy-variational method.The closed-form solutions for stress,deflection and slip of box beams under lateral loading were obtained,and the comparison of the analytical results and the experimental results for steel-concrete composite box beams under concentrated loading or uniform loading verifies the closed-form solution.The investigation of the parameters of load effects on composite box beams shows that:1) Slip stiffness has considerable impact on mid-span deflection and end slip when it is comparatively small;the mid-span deflection and end slip decrease significantly with the increase of slip stiffness,but when the slip stiffness reaches a certain value,its impact on mid-span deflection and end slip decreases to be negligible.2) The shear deformation has certain influence on mid-span deflection,and the larger the load is,the greater the influence is.3) The impact of shear deformation on end slip can be neglected.4) The strain of bottom plate of steel beam decreases with the increase of slip stiffness,while the shear lag effect becomes more significant.

A new 3-D element formulation on displacement of steel-concrete composite box beam

Slip of a composite box beam may reduce its stiffness, enlarge its deformation and affect its performance. In this work, the governing differential equations and boundary conditions of composite box beams were established. Analytic solutions of combined differential equations were also established. Partial degree of freedom was adopted to establish a new FEA element of three-dimensional beam, taking into account the slip effect. Slip and its first-order derivative were introduced into the nodes of composite box beams as generalized degree of freedom. Stiffness matrix and load array of beam elements were established. A three-dimensional nonlinear calculation program was worked out. The results show that the element is reliable and easy to divide and is suitable for special nonlinear analysis of large-span composite box beams.

Nonlinear finite element analysis of steel-concrete composite beams

Proposes a simplified finite element model for steel-concrete composite beams. The effects of slip can be taken into account by creating a special matrix of shear connector stiffness and using the iteration method. Meanwhile, the effect of material non-linearity of steel and concrete on rigidity and strength of composite beams is considered. With the age-adjusted effective modulus method, the analysis for the whole process of shrinkage and creep under long-term load can be performed. The ultimate load, deflection, stress and slip of continuous composite beams under short-term and long-term load are computed using the proposed finite element model. The numerical results are compared with the experimental results and existing values based on other numerical methods, and are found to be in good agreement.

Mechanical performance of shear studs and application in steel-concrete composite beams

This work experimentally investigates the effects of shear stud characteristics on the interface slippage of steel-concrete composite push-out specimens. ABAQUS is used to establish a detailed 3D finite element(FE) model and analyze the behavior of push-out specimens. The modeling results are in good agreement with the experimental results. Based on parametrical analysis using the validated FE approaches, the effects of important design parameters, such as the diameter, number, length to diameter ratio, and yield strength of studs, concrete strength and steel transverse reinforcement ratio, on the load-slip relationship at the interface of composite beams are discussed. In addition, a simplified approach to model studs is developed using virtual springs with an equivalent stiffness. This approach is demonstrated to be able to predict the load-displacement response and ultimate bearing capacity of steel-concrete composite beams. The predicted results show satisfactory agreement with experimental results from the literature.

Distortional buckling analysis of steel-concrete composite box beams considering effect of stud rotational restraint under hogging moment

Restrained distortional buckling is an important buckling mode of steel-concrete composite box beams(SCCBB)under the hogging moment.Rotational and lateral deformation restraints of the bottom plate by the webs are essential factors affecting SCCBB distortional buckling.Based on the stationary potential energy principle,the analytical expressions for the rotational restraint stiffness(RRS)of the web upper edge as well as the RRS and the lateral restraint stiffness(LRS)of the bottom plate were derived.Also,the SCCBB critical moment formula under the hogging moment was derived.Using twenty specimens,the theoretical calculation method is compared with the finite-element method.Results indicate that the theoretical calculation method can effectively and accurately reflect the restraint effect of the studs,top steel flange,and other factors on the bottom plate.Both the RRS and the LRS have a nonlinear coupling relationship with the external loads and the RRS of the web’s upper edge.Under the hogging moment,the RRS of the web upper edge has a certain influence on the SCCBB distortional buckling critical moment.With increasing RRS of the web upper edge,the SCCBB critical moment increases at first and then tends to be stable.

Bending Stiffness of Truss-Reinforced Steel-Concrete Composite Beams

This paper is concerned with a special steel-concrete composite beam in which the resisting system is a truss structure whose bottom chord is made of a steel plate supporting the precast floor system. This system works in two distinct phases with two different resisting mechanisms: during the construction phase, the truss structure bears the precast floor system and the resisting system is that of a simply supported steel truss;once the concrete has hardened, the truss structure becomes the reinforcing element of a steel-concrete composite beam, where it is also in a pre-stressed condition due to the loads carried before the hardening of concrete. Within this framework, the effects of the diagonal bars on the bending stiffness of this composite beam are investigated. First, a closed-form solution for the evaluation of the equivalent bending stiffness is derived. Subsequently, the influence of geometrical and mechanical characteristics of shear reinforcement is studied. Finally, results obtained from parametric and numerical analyses are discussed.

Seismic performance of double-skin steel-concrete composite box piers: Part Ⅱ—Nonlinear finite element analysis

An accurate finite element （ FE） model was constructed to examine the hysteretic behavior of double-skin steel-concrete composite box （ DSCB） piers for further understanding the seismic performance of DSCB piers; where the local buckling behavior of steel tubes, the confinement of the in-filled concrete and the interface action between steel tube and in-filled concrete were considered. The accuracy of the proposed FE model was verified by the bidirectional cyclic loading test results. Based on the validated FE model, the effects of some key parameters, such as section width to steel thickness ratio, slenderness ratio, aspect ratio and axial load ratio on the hysteretic behavior of DSCB piers were investigated. Finally, the skeleton curve model of DSCB piers was proposed. The numerical simulation results reveal that the peak strength and elastic stiffness decrease with the increase of the section width to steel thickness ratio. Moreover, the increase of the slenderness ratio may result in a significant reduction in the peak strength and elastic stiffness while the ultimate displacement increases. The proposed skeleton curve model can be taken as a reference for seismic performance analyses of the DSCB piers.

Experimental study on seismic behaviors of steel-concrete composite frames

Steel-concrete composite frames are seeing increased use in earthquake region because of their excellent structural characteristics, including high strength, stiffness, and good ductility. However, there exist gaps in the knowledge of seismic behavior and the design provisions for these structures. In order to better understand the seismic behaviors of composite frame systems, eight steel-concrete composite frames were designed. These composite frames were composed of steel-concrete composite beams and concrete filled steel tube columns. The axial compression ratio of column, slenderness ratio and linear stiffness ratio of beam to column were selected as main design parameters. The low reversed cyclic loading tests of composite frame system were carried out. Based on test results, the seismic behaviors of composite frames such as failure mode, hysteresis curve, strength degradation, rigidity degradation, ductility and energy dissipation were studied. Known from the test phenomenon, the main cause of damage is the out-of-plane deformation of steel beam and the yielding destruction of column heel. The hysteretic loops of composite frame appear a spindle shape and no obvious pinch phenomenon. The results demonstrate that this type of composite frame has favorable seismic behaviors. Furthermore, the effects of design parameters on seismic behaviors were also discussed. The results of the experiment show that the different design parameter has different influence rule on seismic behaviors of composite frame.

The Study of Force and the Mechanical Characteristic of Incremental Launching Construction Method on a Steel-Concrete Continuous Beam Bridge

The usage of steel-mixed composite beams is quite extensive today.During an event of constructing steel-mixed composite bridges,the incremental launching construction method is generally adopted.This paper mainly analyzes the force of incremental launching construction on a steel-concrete continuous beam bridge,the classification of incremental launching construction,the application of incremental launching construction in steel-mixed composite beams,the temporary facilities existing in incremental launching construction as well as their existing problems.Lastly,the analysis of the stress of composite beams in incremental launching construction is described by using the reference for the construction of mixed composite continuous beam bridges provided.

Seismic performance of double- skin steel- concrete composite box piers: Part Ⅰ——Bidirectional quasi-static testing

To study the seismic performance of double-skin steelconcrete composite box（ DSCB） piers, a total of 11 DSCB pier specimens were tested under bidirectional cyclic loading. The effects of the loading pattern, the steel plate thickness, the axial load ratio, the slenderness ratio and the aspect ratio were taken into consideration. The damage evolution process and failure modes of the tested specimens are presented in detail. Test results are also discussed in terms of the hysteretic curve, skeleton curve, ductility and energy dissipation capacity of DSCB pier specimens. It can be concluded that the hysteretic performance of DSCB piers in one direction is affected and weakened by the cyclic loading in the other direction. DSCB piers under bidirectional cyclic loading exhibit good performance in terms of load carrying capacity, ductility, and energy dissipation capacity. Overall, DSCB piers can meet the basic aseismic requirements. The research results can be taken as a reference for using DSCB piers as high piers in bridges in strong earthquakeprone areas.

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.

装配式槽钢组合梁中开孔钢板连接件力学性能

为研究新型装配式双拼槽钢-混凝土组合梁中开孔钢板剪力连接件(PSP剪力连接件)的力学性能,设计7组标准试件并开展推出试验,对比分析不同参数PSP剪力连接件的受剪承载力和破坏模式。利用ABAQUS非线性有限元模型对PSP剪力连接件的破坏模式和受力机制进行数值模拟,并与试验结果对比验证计算结果的可靠性。在此基础上,进一步分析开孔钢板厚度、开孔直径、混凝土强度、穿孔钢筋及连接件间距对PSP剪力连接件力学性能的影响。结果表明:除10 mm厚度的PSP剪力连接件外,所有4 mm与6 mm厚度的PSP剪力连接件均发生明显弯曲变形,试件破坏时连接件周围混凝土均出现斜向裂缝;开孔直径和穿孔钢筋对受剪承载力和抗剪刚度影响较小,而增加开孔钢板厚度、混凝土强度能提高剪力连接件受剪承载力和抗剪刚度;对于双排PSP剪力连接件,增大连接件间距能够显著提高单排PSP剪力连接件平均承载力,当间距为250 mm时,单排平均承载力达到单个PSP剪力连接件的91.2%。根据试验及有限元荷载滑移曲线提出装配式双拼槽钢-混凝土组合梁中单个PSP连接件荷载滑移曲线计算公式,为装配式双拼槽钢混组合梁的设计提供参考。

车辆荷载作用下钢-混凝土组合梁疲劳应力分析

【目的】随着桥梁服役期延长和车辆荷载增加等多种因素的影响,结构承载力会变得越来越弱,疲劳寿命不断降低,最终可能导致低应力疲劳破坏。因此有必要对车辆荷载下拱桥钢混组合梁的疲劳细节应力进行研究。【方法】采用数值模拟的方法,利用Midas FEA NX软件建立3个标准长度的三维实体精细有限元模型,分析钢混组合梁易损疲劳关键点的位置,并研究车辆荷载横向最不利加载位置和纵向加载下的疲劳细节应力变化规律。【结果】结果表明,组合梁次横梁与中纵梁交点处有三处疲劳关键点;靠近桥梁中线位置是车辆荷载下钢梁疲劳最不利的横向加载位置;四种不同标准的纵向车辆加载时,三个疲劳关键点均出现两次应力峰值,且最大应力幅值均低于常幅疲劳强度的极限值。【结论】研究成果可为钢-混凝土组合梁试验和相关研究提供参考。

装配式组合梁新型剪力键受力性能试验研究

为解决装配式组合梁剪力键存在的问题,通过在预制混凝土桥面板中预埋栓钉和钢板,再与钢梁翼缘焊接的方式改进剪力键的设计,并对新型栓钉剪力键试件进行推出试验,研究其破坏形态、荷载-滑移曲线、抗剪刚度等。结果表明:试件破坏时栓钉均被剪断,表现出延性破坏;试件的荷载-滑移曲线可以划分为弹性阶段、弹塑性阶段和破坏阶段3个阶段;在相对滑移量约为2 mm时,试件达到极限承载力,随着栓钉数目的增加,栓钉的承载力和抗剪刚度均减小。通过计算可知,该新型栓钉剪力键的承载力能够满足工程设计的需要。

轨道运梁车在宽幅平面双钢箱组合梁运输中的应用

以甘肃省兰州市某公路工程建设项目桥梁工程上部钢-混组合箱梁结构的安装施工为例,通过对宽幅平面双钢箱组合梁安装运输工况进行理论分析,从桥头待架区向已架设桥跨上引出两组钢轨,由三维空间位置可调式运梁装置运输平曲线钢箱组合梁,总结了平曲线宽幅双钢箱组合梁的运输安装施工技术。论文主要从工艺技术原理、施工准备、测量放样、桥头路基段轨道基础施工、轨道铺设及加固、轨道连接、运梁平车运输钢箱梁、箱梁架设等内容对双钢箱组合梁运输技术进行了阐述。

S型曲线小半径连续窄箱室钢混组合梁设计要点及受力研究

文章依托某项目4 m×45 m连续窄箱室钢混组合梁,介绍了连续窄箱室钢混组合梁的构造设计,采用有限元软件进行数值分析。设计出一种窄箱式钢梁和有承托混凝土桥面板结合的钢混组合梁截面形式。钢混组合梁增大了组合截面的刚度,减小了梁的挠度;提高了梁的基频,利于结构的抗震设计;整个截面重心的抬高,钢梁的腹板较大一部分处于受拉区,避免钢梁腹板产生“呼吸效应”。文章总结了钢混组合梁较常规结构的优缺点,构造上经优化后可为同类型桥梁方案提供设计参考。

横向骑跨既有地道曲线宽幅梁拱组合体系桥梁设计与分析

文章以广东省深圳市前海合作区临海桂湾河桥为背景,对异形梁拱组合体系桥梁的设计特点与施工方法进行介绍。桂湾河桥桥位处地形复杂,桩基布置需避开地下通道等构筑物,设计方案最终确定为86.84 m+124.65 m下承式梁拱组合体系桥,并采用骑跨式转换梁跨越地下通道,主梁、拱肋及转换梁构成整体,共同参与结构受力。桥梁平面位于曲线段;主梁采用封闭的正交异形钢箱梁,桥宽56.2 m~57.8 m,桥面宽度较大,按使用功能横向分为四幅桥设计,结构受力复杂;拱肋由大拱和小拱组成,拱肋之间无风撑连接;吊索采用高强钢丝高钒密封索,结构紧凑,性能稳定,在国内首次应用到大跨径桥梁中。采用有限元分析方法,验证了设计的合理性与施工方法的可行性,可为类似桥梁设计与施工提供借鉴。