Approach for analyzing the ultimate strength of concrete filled steel tubular arch bridges with stiffening girder

A convenient approach is proposed for analyzing the ultimate load carrying capacity of concrete filled steel tubular (CFST) arch bridge with stiffening girders. A fiber model beam element is specially used to simulate the stiffening girder and CFST arch rib. The geometric nonlinearity, material nonlinearity, influence of the construction process and the contribution of prestressing reinforcement are all taken into consideration. The accuracy of this method is validated by comparing its results with experimental results. Finally, the ultimate strength of an abnormal CFST arch bridge with stiffening girders is investigated and the effect of construction method is discussed. It is concluded that the construction process has little effect on the ultimate strength of the bridge.

Improved methods for decreasing stresses of concrete slab of large-span through tied-arch composite bridge

Mechanical behavior of concrete slab of large-span through tied-arch composite bridge was investigated by finite element analysis (FEA). Improved methods to decrease concrete stresses were discussed based on comparisons of different deck schemes, construction sequences and measures, and ratios of reinforcement. The results show that the mechanical behavior of concrete slab gets worse with the increase of composite regions between steel beams and concrete slab. The deck scheme with the minimum composite region is recommended on condition that both strength and stiffness of the bridge meet design demands under service loads. Adopting in-situ-place construction method, concrete is suggested to be cast after removing the full-supported frameworks under the bridge. Thus, the axial tensile force of concrete slab caused by the first stage dead load is eliminated. Preloading the bridge before concrete casting and removing the load after the concrete reaching its design strength, the stresses of concrete slab caused by the second stage dead load and live load are further reduced or even eliminated. At last, with a high ratio of reinforcement more than 3%, the concrete stresses decrease obviously.

Analysis on Construction Technology of Reinforced Concrete Tied Arch Bridge

Bridge construction has received a lot of attention as transportation continues to improve.Reinforced concrete linked arch bridges are a common bridge style in today’s bridge construction.This type of bridge not only has a basic and generous shape,but it is also incredibly easy to construct,resulting in significant material and construction cost savings.This article analyzes the construction technology of a reinforced concrete linked arch bridge in order to achieve good construction and application.It is hoped that this analysis can provide a scientific reference for the guarantee of the construction quality and subsequent application effect of this kind of bridge.

Longitudinal force in continuously welded rail on long-span tied arch continuous bridge carrying multiple tracks

Considering arch rib, lateral brace, suspender, girder, pier and track position, the model for the interaction between long-span tied arch continuous bridge and multiple tracks was established by using steel-concrete composite section beam element to simulate concrete-filled steel tube(CFST) arch rib, using the beam element with rigid arm to simulate the prestressed concrete girder and using nonlinear bar element to simulate longitudinal constraint between track and bridge. Taking a(77+3×156.8+77) m tied arch continuous bridge with four tracks on the Harbin-Qiqihar Passenger Dedicated Line as an example, the arrangement of continuously welded rail(CWR) was explored. The longitudinal force in CWR on the tied arch continuous bridge, the pier top horizontal force and torque due to the unbalance load case, were analyzed under the action of temperature, vertical live load, train braking and wind load.Studies show that, it can significantly reduce track displacement to set the track expansion devices at main span arch springing on both sides; the track stress due to arch temperature variation can reach 40.8 MPa; the track stress, pier top horizontal force and torque are related to the number of loaded tracks and train running direction, and the bending force applied to unloaded track is close to the loaded track, while the braking force applied to unloaded track is 1/4 to 1/2 of the loaded track; the longitudinal force of track due to the wind load is up to 12.4 MPa, which should be considered.

The New Arched Bridge over Dnipro in Kyiv

The Podilskyi Arch bridge is crossing the Dnipro River in center of Kiev and is part of a 7.4 km long link which connects the center of Kiev with the “sleeping district” on the left bank of the river. The bridge has a main span of 344 m intended for six lanes of vehicles in the top level and two metro lines in the bottom level plus large diameter water pipes. The bridge is of steel, except of the reinforced concrete bases of the lower parts of the arches. The draft design works began in 1991 and in 2005 parallel design and construction work started. Due to the financial crisis in Ukraine, the work was interrupted for several years but construction recommenced in 2018 and the bridge is now planned to be completed in 2020 and the first stage of the transition in 2022.

Typical diseases of a long-span concrete-filled steel tubular arch bridge and their effects on vehicle-induced dynamic response

A long-span concrete-filled steel tubular(CFST)arch bridge suffers severe vehicle-induced dynamic responses during its service life.However,few quantitative studies have been reported on the typical diseases suffered by such bridges and their effects on vehicle-induced dynamic response.Thus,a series of field tests and theoretical analyses were conducted to study the effects of typical diseases on the vehicle-induced dynamic response of a typical CFST arch bridge.The results show that a support void results in a height difference between both sides of the expansion joint,thus increasing the effect of vehicle impact on the main girder and suspenders.The impact factor of the displacement response of the main girder exceeds the design value.The variation of the suspender force is significant,and the diseases are found to have a greater effect on a shorter suspender.The theoretical analysis results also show that the support void causes an obvious longitudinal displacement of the main girder that is almost as large as the vertical displacement.The support void can also cause significant changes in the vehicle-induced acceleration response,particularly when the supports and steel box girder continue to collide with each other under the vehicle load.

瓮马铁路乌江特大桥设计关键技术研究

新建瓮马铁路乌江特大桥跨越两山之间深谷,地形复杂、设计难度大。为研究该桥梁方案,首先阐述了主桥的方案构思和结构设计,然后通过空间有限元软件对本桥进行静、动力仿真分析,总结了大跨铁路劲性骨架混凝土拱桥构造和受力特性。结果表明:主跨337 m上承式劲性骨架混凝土拱桥具有刚度大、徐变小、后期养护维修工作量小等优点,主拱圈采用小矢跨比设计,兼顾安全、经济、环保和美观,能够满足铁路桥梁跨越山区“V”形峡谷的要求;主拱圈由劲性钢管混凝土骨架外包C55无收缩混凝土构成,通过分层分段浇筑方案改善拱圈各构件的内力;拱上结合梁采用两片工字形钢与混凝土桥面板相结合的形式,钢梁栓焊结合,便于制造、运输和施工;拱座采用梯形断面扩大基础,基础开挖永临结合,有效降低施工风险;数值分析表明该桥结构的刚度、强度、稳定性均能满足规范要求,能够满足客货共线铁路的安全性和乘坐舒适性要求。可为其他山区铁路桥梁桥式研究提供参考。

Numerical Simulation Analysis of Welded Joints in Arch Ribs of Large Span Steel Pipe Arch Bridges

In order to study the residual stress distribution law of welded joints of arch ribs of large-span steel pipe concrete arch bridges,numerical simulation of temperature,stress and strain fields based on ABAQUS for welded joints of arch-ribbed steel tubes using 7-,8-and 9-layer welds is carried out and its accuracy is demonstrated.The steel pipe welding temperature changes,residual stress distribution,different processes residual stress changes in the law,the prediction of post-weld residual stress distribution and deformation are studied in this paper.The results show that the temperature field values and test results are more consistent with the accuracy of numerical simulation of welding,the welding process is mainly in the form of heat transfer;Residual high stresses are predominantly distributed in the Fusion zone(FZ)and Heat-affected zone(HAZ),with residual stress levels tending to decrease from the center of the weld along the axial path,the maximum stress appears in the FZ and HAZ junction;The number of welding layers has an effect on the residual stress distribution,the number of welding layers increases,the residual stress tends to decrease,while the FZ and HAZ high stress area range shrinks;Increasing the number of plies will increase the amount of residual distortion.

长阳天池口清江特大桥主拱圈悬臂浇筑斜拉扣挂系统设计

长阳天池口清江特大桥主桥为净跨径242 m的非对称上承式钢筋混凝土拱桥,主拱圈采用单箱单室截面,宽9.5 m、高4.0 m。资丘岸和五峰岸半跨主拱圈各分为24个和21个节段,第1个节段采用支架现浇,其余节段采用斜拉扣挂悬臂浇筑法施工。扣索采用星式和扇形组合方式布置,位于墩顶和扣塔的扣索为星式布置,位于交界墩墩身的扣索为扇形布置,并将墩身上的扣锚索设计成连续索以避免在墩身上搭设张拉平台;扣塔由8根∅800 mm×16 mm钢管组成,两岸扣塔分别高52.68 m和60.12 m;根据锚索最大索力,设计了能承受800 kN张拉力的岩锚索。建立主拱圈悬臂浇筑施工阶段MIDAS Civil有限元模型,对斜拉扣挂系统扣锚索索力进行计算,通过拆除部分扣索和调整扣锚索索力,施工期间主拱圈截面最大拉应力、扣塔最大偏位、主拱圈成拱后线形均满足要求。

钢筋混凝土拱桥主拱圈加固方式及效果研究

目的 寻求钢筋混凝土拱桥主拱圈最佳加固方式,以改善加固效果,给同类危旧拱桥加固提供参考。方法 基于某实际加固桥例提出3种不同卸载方式的加固改造方案,采用Midas civil软件建立有限元模型,分析不同加固方式的影响规律;对原拱圈初始应力水平、施工阶段内力、成桥状态下应力、内力及挠度进行分析;利用加固层最大应力比、荷载置换率和挠度变化率对加固效果进行评价。结果 方案三的加固层最大应力比分别比方案一、二大45.12%与52.74%,荷载置换效果最显著,最大值达3.82,挠度变化率最大。结论 选择拱上建筑拆除得越多的方式进行加固,加固效果越好;对钢筋混凝土拱桥进行加固时,应基于加固方式制定加固施工方案,同时需考虑施工工期与加固成本。

钢筋混凝土拱桥加固施工次序方案及效果评价

为研究钢筋混凝土拱桥最优的加固施工次序,以一座在役4跨箱形拱桥的加固方案为背景,设计了3组针对性的加固方案,并对不同拆除加固施工次序下的主拱圈力学性能进行了分析;采用恒载应力变化率(αD)和荷载效应变化率(αN)评价了施工中拱圈的应力变化规律及加固后原拱圈的荷载效应。研究结果表明:拱上结构的拆建次序对加固后主拱圈的力学性能影响较小,但对加固过程中主拱圈的受力状态影响较大;拱顶对称拆除时αD<0,结构处于“卸载”状态,有利于拱桥施工中的受力;αN随着拱上结构恒载减小而增大,且增速减缓,故加固层材料利用率也随拱上结构恒载减小而增大,且增幅变缓;αN越大,则加固效果越好。

外包钢壳混凝土拱形桥塔节段拼装几何姿态预测研究

赣州市集结大桥主桥为外包钢壳混凝土拱形桥塔斜拉桥,为确保钢混组合拱形桥塔节段拼装精准合龙,采用MIDAS Civil软件建立拱形桥塔空间几何模型,分析外包钢壳和混凝土湿重对桥塔变形的影响,采用切线初始位移法对桥塔施工阶段位移进行预测,通过求解制造线形对桥塔待拼装节段进行预偏修正,并与实测数据进行对比。结果表明:外包钢壳能显著减小桥塔变形;施工阶段桥塔变形主要由混凝土湿重引起,临时支撑能有效减小混凝土浇筑产生的横向变形。基于切线初始位移法的几何姿态预测方法能有效预测桥塔拼装全过程几何姿态,实测成桥阶段桥塔各节段最大偏位为6 mm,小于施工控制要求,具有较高的实施精度,可保证成桥状态下桥塔几何姿态的准确性。

100 m~150 m跨混凝土拱桥基于特定钢拱架的预拱度快速计算方法

针对100 m~150 m跨混凝土拱桥所采用的特定钢拱架的预拱度计算问题,提出了一种用拱圈自重变形和钢拱架变形比值快速计算钢拱架预拱度的方法。为了得到不同矢跨比和拱轴系数下的钢拱架变形比值,编写了通过导入MCT文件建立Midas/Civil有限元模型的辅助程序,实现从单元、边界条件、施工阶段和施工阶段联合截面定义的全过程快速建模,对拱圈混凝土分底板、腹板、顶板三环浇筑,考虑钢拱架与拱圈的联合作用,给出了钢拱架预拱度计算公式。计算结果表明,对于常用矢跨比和拱轴系数的混凝土拱桥,拱圈分环浇筑变形与拱圈自重变形比值的平均值为4.37~4.88,为方便钢拱架弹性变形计算,建议变形比值统一取5.0。将该方法应用于一座净跨径为135 m的混凝土拱桥钢拱架预拱度计算中,得到的钢拱架弹性变形与空间模型结果最大误差为4.30%,满足工程精度要求,表明该方法合理可行,可在混凝土拱桥钢拱架预拱度计算中推广应用。

曲线条件大跨度拱加劲连续梁设计

贵南高铁二塘双线特大桥采用90m+180m+90m拱加劲连续梁结构。大桥位于曲线上,梁体采用分段直线布置,悬灌施工;主拱采用哑铃形钢管混凝土拱肋,钢管直径1 m,拱肋全高3 m;采用整束挤压钢绞线吊杆,全桥拱设置36组吊杆;纵向活动主墩通过构造措施,形成半刚构结构体系,限制部分梁体问题伸缩变形;大桥采用先悬灌主梁,后在主梁上搭设支架原位拼装拱肋方式施工。经论文研究计算结果表明,该桥刚度、受力等均满足规范要求。

中小跨径混凝土3D打印箱型拱桥数字化设计建造

本文对西安市考古公园混凝土3D打印景观拱桥的结构组成及建造方式进行介绍,详细阐述拱桥核心设计元素。拱桥设计基于混凝土3D打印路径规划重构、简化古代青铜器饰纹“雷云纹”,并将其作为拱桥的外观的主元素。结合混凝土3D打印系统的打印能力及拱桥结构特点对拱桥进行优化分块,根据结构设计需求配制打印材料,完成拱桥上部结构设计建造。基于ANSYS软件对该拱桥进行数值模拟,分析其结构强度及动力特性,计算结果表明拱桥各项性能参数符合设计要求。最后结合拱桥打印构件组装和整体安装的特点,对混凝土3D打印箱型拱桥的施工工艺进行阐述。

不均匀温度场下钢管混凝土拱桥管内混凝土脱空分析

为了解不均匀温度场作用下钢管混凝土拱桥管内混凝土脱空原因,依托高原山区某跨径430 m的钢管混凝土拱桥,进行强辐射、大温差联合作用下拱肋拱顶节段足尺模型试验,分析模型温度场分布,并对该不均匀温度场作用下管内混凝土脱空机理进行研究。结果表明:钢管混凝土拱桥水化阶段和运营阶段径向温度场可简化为多段式折线变化规律。14:00时刻,水化阶段温度沿竖直径向(从向阳侧至背阳侧)先减小后升高再减小,在距向阳侧界面D/8~3D/8处(D为钢管内径)存在一个大温差面,运营阶段温度沿竖直径向(从向阳侧至背阳侧)呈先减小后不变再增加的非对称分布规律,从钢管混凝土界面至距其D/8处温度变化大。混凝土水化阶段和运营阶段管内混凝土脱空机理为:在温度场作用下钢管混凝土界面最大纵向应力差分别高达82.6 MPa和61.95 MPa,最大界面径向拉应力分别为0.8 MPa和2.06 MPa,均超过钢管和混凝土间的粘结强度。

大跨度双联连续钢管混凝土拱桥结构体系设计研究

为研究大跨度双联连续钢管混凝土拱桥的合理结构体系及中央拱座合理刚度,以主跨2×405 m渝湘复线双堡特大桥为背景,采用MIDAS Civil软件建立全桥有限元模型,分析考虑自重、汽车荷载和基础沉降作用下,拱桥刚接、铰接、半刚性连接约束体系和不同中央拱座刚度对桥梁力学性能的影响。结果表明:自重、汽车荷载和基础沉降作用下各结构体系力学性能均满足规范要求。双刚接方案拱肋变形对称,结构受力良好,且构造简单、施工方便。中央拱座刚度从0.8 EI(EI为原设计方案中央拱座截面刚度)增加至2.0 EI,自重产生的最大变形基本不变,最大拉应力减小了0.33%,最大压应力减小了0.47%,结构力学性能改善效果不明显。双堡特大桥结构体系推荐采用双刚性连接,中央拱座合理刚度取值为0.8 EI,全桥有限元计算结果表明,该结构体系的强度、刚度、稳定性均满足规范要求。

基于零位移与无应力状态控制的斜拉扣挂施工扣索力确定方法

大跨度拱桥常采用斜拉扣挂法开展拱肋施工,但在节段拼装过程中扣索索力和拱肋空间位形之间互相影响,索力优化计算以及扣索状态控制问题复杂。提出改进零位移法结合无应力状态控制法的复合扣索力计算方法:基于改进型零位移法快速得到满足成拱线形要求的扣索力大小,基于成拱索力采用无应力状态法反推各施工阶段扣索索力。该复合方法可避免传统零位移法扣索力不准和反复迭代计算的缺陷,施工中扣索可实现一次张拉,后续节段拼装中无需对扣索进行索力调整。以某跨径430 m大跨度钢管混凝土拱桥缆扣合一施工为工程应用背景,采用的零位移法结合无应力状态法对大跨度非对称式钢结构拱肋进行斜拉扣挂拼装的扣索力求解和施工模拟。分析拼装过程中扣索力变化规律,并对比验证实际线形与目标线形偏差,以及拱肋应力与设计应力之间偏差程度。结果表明,所提出的复合算法理论简单且索力求解计算便捷。所求的扣索力可有效保证拱肋拼装完成及松索后拱肋线形和受力均满足要求。

张吉怀铁路酉水大桥非对称拱桥钢拱肋架设技术研究

张吉怀铁路酉水大桥主桥为主跨292 m的非对称上承式钢管混凝土拱桥,其钢拱肋采用斜拉扣挂法进行节段悬臂架设施工。本文结合张吉怀铁路酉水大桥工程,针对高速铁路非对称拱桥钢拱肋安装施工技术展开研究,主要包括:复杂地形条件下的施工技术,因地制宜地进行缆索起重机的设计及安装,钢管拱整节段拼装和架设,合龙装置和技术等。该施工技术保障了钢拱肋架设的精度和质量,钢拱肋的成拱线形与设计值较为吻合。该桥运营以来,各结构性能指标均满足设计要求。