Concrete-Filled Steel Tube Arch Bridges in China

In the past 20 years, great progress has been achieved in China in the construction of concrete-filled steel tube （CFST） arch bridges and concrete arch bridges with a CFST skeleton. The span of these bridges has been increasing rapidly, which is rare in the history of bridge development. The large-scale construction of expressways and high-speed railways demands the development of long-span arch bridges, and advances in design and construction techniques have made it possible to construct such bridges. In the present study, the current status, development, and major innovative technologies of CFST arch bridges and concrete arch bridges with a CFST skeleton in China are elaborated. This paper covers the key con- struction technologies of CFST arch bridges, such as the design, manufacture, and installation of steel tube arch trusses, the preparation and pouring of in-tube concrete, and the construction of the world＇s longest CFST arch bridge-the First Hejiang Yangtze River Bridge. The main construction technologies of rein- forced concrete arch bridges are also presented, which include cable-stayed fastening-hanging cantilever assembly, adjusting the load by means of stay cables, surrounding the concrete for arch rib pouring, and so forth. In addition, the construction of two CFST skeleton concrete arch bridges-the Guangxi Yongning Yong River Bridge and the Yunnan-Guangxi Railway Nanpan River Bridge--is discussed. CFST arch bridges in China have already gained a world-leading position; with the continuous innovation of key technologies, China will become the new leader in promoting the development of arch bridges.

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.

In-Plane Creep Buckling of Concrete-Filled Steel Tubular Arches

The creep-induced deformation of the arch rib of concrete-filled steel tubular （CFST） arches under a sustained load can increase the bending moment, which may lead to earlier stability failure called creep buckling. To investigate the influences of concrete creep on the buckling strength of arches, a theoretical analysis for the creep buckling of CFST circular arches under distributed radial load is performed. The simplified Arutyunyan-Maslov （AM） creep law is used to model the creep behavior of concrete core, and the creep integral operator is introduced. The analytical solutions of the time-dependent buckling strength under the sustained load are achieved and compared with the existing formula based on the age-adjusted effective modulus method （AEMM）. Then the solutions are used to determine the influences of the steel ratio and the first loading age on the creep buckling of CFST arches. The results show that the analytical solutions are of good accuracy and applicability. For CFST arches, the steel ratio and the first loading age have significant influences on creep buckling. An approximate log-linear relationship between the decreased degrees of the creep buckling strength and the first loading age is found. For the commonly used parameters, the maximum loss of the buckling strength induced bv concrete creen is close to 40%

Recent Construction Technology Innovations and Practices for Large-Span Arch Bridges in China

Arch bridges provide significant technical and economic benefits under suitable conditions.In particular,concrete-filled steel tubular(CFST)arch bridges and steel-reinforced concrete(SRC)arch bridges are two types of arch bridges that have gained great economic competitiveness and span growth potential due to advancements in construction technology,engineering materials,and construction equipment over the past 30 years.Under the leadership of the author,two record-breaking arch bridges—that is,the Pingnan Third Bridge(a CFST arch bridge),with a span of 560 m,and the Tian’e Longtan Bridge(an SRC arch bridge),with a span of 600 m—have been built in the past five years,embodying great technological breakthroughs in the construction of these two types of arch bridges.This paper takes these two arch bridges as examples to systematically summarize the latest technological innovations and practices in the construction of CFST arch bridges and SRC arch bridges in China.The technological innovations of CFST arch bridges include cable-stayed fastening-hanging cantilevered assembly methods,new in-tube concrete materials,in-tube concrete pouring techniques,a novel thrust abutment foundation for nonrocky terrain,and measures to reduce the quantity of temporary facilities.The technological innovations of SRC arch bridges involve arch skeleton stiffness selection,the development of encasing concrete materials,encasing concrete pouring,arch rib stress mitigation,and longitudinal reinforcement optimization.To conclude,future research focuses and development directions for these two types of arch bridges are proposed.

Experimental Study on Shear Behavior of New-Type Steel-Concrete Composite Bridge Deck

To alleviate deck fatigue failure and regular pavement damage,which are congenital deficiencies of highway steel bridge deck structure,this paper proposes a newtype of composite bridge deck,consisting of steel tubular connectors and steel-reactive powder concrete (RPC). Push-out tests were conducted to study the newdeck's shear performance. During the experimental process,specimens were divided into two groups which are composed of steel tubular connectors with or without penetrative bars set in. Then,researchers analyzed destroyed models and mechanisms of the composite structure under shear forces. Results showed that test models in two groups,once destroyed,displayed similar shear fracture,which appeared on the lower margin of the steel tubular wall along the welds. Meanwhile,RPC under the connector,for varied tests,was crushed at the same stage,although the large shear and bending deformation just occurred on connectors with penetrative bars. Additionally,shear capacity of specimens with penetrative bars,compared with the ones without bars,unexpectedly decreased by 20%,but the structural ductility was 1.75 times as much,and the ductility coefficients of specimens were all larger than 3.5,demonstrating certain deformation capacity.

A method for examining the seismic performance of steel arch deck bridges

To examine the seismic resistance performance of a steel arch bridge during a strong earthquake,an approach is proposed in this paper to determine the ultimate strain of an arch rib using the static elasto-plastic large deformation theory.A steel fixed-end deck arch bridge with a span length of 200 m was used as an example in this study.The ultimate strain of the arch rib was calculated using the elasto-plastic finite element model.The seismic responses of the arch bridge exposed to strong earthquakes in two and three directions were also simulated.Moreover,the effect of earthquake motion in the lateral direction on the elasto-plastic earthquake response was discussed,and the seismic resistance of the structure was analyzed.The results show that steel arch bridges have preferable seismic resistance under strong earthquake conditions.While lateral earthquake motion has some influence on the damage to an arch bridge,it has little effect on the displacement,axial force,and bending moment responses of the arch rib.It is feasible to examine the seismic performance of the arch bridge by ascertaining the out-of-plane and in-plane earthquake responses of the bridge.

山区拱桥双层无缆塔缆索吊施工技术

平绵高速武都至九寨沟段尖山沟特大桥主桥为主跨220 m的上承式钢管混凝土拱桥,左、右幅分离式布置,两幅净间距30 m。大桥位于U形山谷,不具备支架法施工条件,拱肋采用缆索吊及扣挂法悬臂拼装,其它构件均采用缆索吊安装。从材料设备投入、吊装覆盖范围、施工进度及操作难度方面,对缆扣合建、缆扣分离和无缆塔缆索吊方案进行比选,推荐采用无缆塔缆索吊作为实施方案。在60 t主缆索吊上方设置1台15 t辅助工作缆索吊,形成双层无缆塔缆索吊系统,进行缆索吊锚碇构件运输安装;为节约缆索吊成本,利用桥位山体设置主索可横移锚碇,通过缆索吊主索横移实现单组主索横移分榀安装钢管拱肋。双层无缆塔缆索吊立体同步作业,提高了施工效率。

先梁后拱施工技术在钢结构系杆拱桥施工中的应用

下承式钢结构系杆拱桥以其独特的结构特性,在市政和公路工程中得到了广泛应用。结合上海市临洮路吴淞江桥的施工,进一步深入分析“先梁后拱”施工技术在大跨度下承式钢结构系杆拱桥施工中的应用,详细介绍“先梁后拱”的施工流程、关键工序、施工监控等施工技术,旨在为桥梁工程领域类似工程提供技术参考与实践指导。

Simplified Algorithm for Out-of-Plane Critical Loads of CFST Solid-Rib Arch

The simplified algorithm for out-of-plane ultimate loadcarrying capacity of concrete-filled steel tubular( CFST) solid-rib arches under uniform vertical load was studied. The experimentally validated finite element model was developed. The out-of-plane equivalent length coefficients of solid-rib arches were obtained using out-of-plane elastic eigenvalue buckling analysis. Then the out-ofplane elastic stability coefficient was plotted against the normalized slenderness ratio,and the out-of-plane eigenvalue buckling load or elastic buckling capability of arches was calculated. Lastly effects of different parameters on the out-of-plane ultimate load-carrying capacity of CFST solid-rib arches were determined using geometric and material nonlinear finite element analysis, and a simplified algorithm was established by fitting the out-of-plane elastic-plastic stability coefficient and normalized slenderness ratio using PerryRobertson formula. Ratio of the elastic stability coefficient to the elastic-plastic counterpart was plotted against the out-of-plane normalized slenderness ratio,from which the out-of-plane elasticplastic ultimate load-carrying capacity was determined according to the corresponding elastic buckling load. Results show that the proposed simplified algorithm can accurately predict the out-of-plane eigenvalue buckling load and the elastic-plastic ultimate loadcarrying capacity of the CFST solid-rib arches.

大倾角钢箱提篮拱桥总体设计

考虑施工技术、经济性和景观效果等方面,陕西蔡家坡渭河特大桥主桥采用(35+210+35) m大倾角钢箱提篮拱桥。该桥采用摩擦摆和环向钢丝绳阻尼支座综合减隔震约束体系,以降低结构的地震响应。拱肋为单室等宽钢箱截面,采用主、副拱肋2条悬链线,主、副拱肋共面,设计为横向内倾20°的大倾角,在提高桥梁景观效果的同时,又有效提高了结构的整体稳定性;拱肋设钢-混结合段连接拱脚与混凝土拱座。桥面系采用自重较轻的正交异性钢桥面板结构。吊杆采用抗拉强度1 860 MPa的环氧柔性钢绞线。基础采用Φ2.5 m的钻孔灌注群桩,以抵抗软弱地质条件下荷载的竖向及水平作用力。该桥总体采用先梁后拱的施工方案。整体及局部有限元分析结果表明,桥梁结构力学性能均满足规范要求,设计安全可靠。

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。

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。

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。

几何初始缺陷与初应力对钢管混凝土拱桥的影响研究

为探讨拱圈拱轴线的几何初始缺陷和钢管初应力对拱桥结构内力与应力的影响,基于实际工程案例,建立了4个有限元模型,分为2组,一组包括2个模型,考虑了拱轴线的几何初始缺陷影响;另一组也包括2个模型,首先考虑拱轴线几何初始缺陷,然后在此基础上考虑初应力影响,进行拱桥内力和应力分析对比。结果表明:几何初始缺陷对拱圈轴力影响较小,增幅<1%,但对拱圈的弯矩和应力分布影响较明显,特别是在拱顶部分,在拱顶处弯矩减小高达91.31%,而拱脚处增加17.03%,拱脚和拱顶上缘的混凝土应力增加23.19%,下缘的混凝土应力减小51.95%;考虑初应力影响后,拱桥内力分布发生显著变化。拱脚处轴力增加65.5%,拱圈弯矩最大减小68.21%,拱圈截面上缘应力增加幅度高达113.7%。因此,实际施工阶段,必须充分考虑拱圈拱轴线几何初始缺陷影响,并根据实际施工顺序准确模拟初应力。

上承式梁拱组合钢结构桥梁施工研究

为减少桥梁上部结构自重,获得更大的桥下净空,引入钢结构桥梁建设思路,开展上承式梁拱组合钢结构桥梁施工研究。在明确工程概况,完成对吊装施工方案的比选后,通过拼装支架搭设、施工中的合拢控制、支架预拱度设置与沉降消除、龙门吊安装,完成施工。在此基础上,对新的施工技术进行了总结,以期对同类工程的建设起到一定的借鉴作用。

BIM技术在钢管混凝土拱桥施工过程中的应用

钢管混凝土拱桥是大跨度桥梁中目前采用比较普遍的一种结构形式,但因其形体结构复杂、设计方案多样,也给施工带来了较大的困难和挑战。在该类型大桥施工过程中,描述了依托BIM技术辅助进行大体积混凝土温控抗裂研究、缆索吊装施工技术交底、预制构件施工深化加工与管理、施工过程信息化等方面的应用,为后续类似工程施工信息化管理提供借鉴。

南华水库大桥主跨结构的选型与动力特性分析

瑞梅铁路南华水库大桥设计时速160 km/h,铺设有砟轨道。根据地方环保要求,该桥主桥跨度需要达到150 m。本文结合现场情况,综合考虑技术、工程造价、施工难易、后期养护等因素,对上承式拱桥、V构、背索单跨斜拉桥、斜拉桥四种桥型综合比选,最终确定上承式拱桥为最佳方案。为了增加拱桥稳定性,本文引入了新型的拱肋截面形式-芯板式钢-混组合拱桥;同时与常见的上承式混凝土拱结构进行静力分析、动力特性分析、弹性稳定性分析对比,验证了其结构的安全性和稳定性。计算结果表明,上承式芯板式钢-混组合拱桥适用于铁路桥梁。芯板式钢-混组合拱桥是很有发展潜力的新型大跨度拱桥结构形式,该桥型首次应用于铁路建设后,能够为铁路桥梁设计提供新的思路,促进大跨桥梁的再发展。

大跨度蝶形钢结构组合桥梁设计与施工

丽水好溪特大桥主桥为跨径208 m蝶形钢结构组合桥梁,该桥采用先梁后拱、缆索吊拼装方式施工,钢拱系统由主、副拱肋及其连杆、风撑组成,主梁梁格体系由主纵梁、横梁、正交异性钢桥面板等组成。为平衡成桥状态钢拱系统推力,每个主纵梁内均设置可换索式体外束系杆;每个吊点设2根镀锌平行钢丝成品吊索,上下均采用叉耳销轴式锚固。有限元计算结果表明,主梁、拱肋、吊索受力均满足规范要求。

陡峭山区大跨度钢管拱桥悬臂拼装抗风性能及稳定性分析

山区隘口风速大,对桥梁施工安全构成重大风险。文中结合某陡峭山区大跨度钢管混凝土拱桥施工项目,研究不同风速条件下静风荷载三分量对结构的影响程度和设置浪风索对提高结构稳定性的效果。针对浪风索初始拉应力较小、垂度大导致的浪风索刚度弱的问题,运用几何非线性数值分析方法,通过修正浪风索弹性模量,探讨不同风速条件下施工阶段钢管拱桥悬臂拼装受力性能和抗风稳定性。分析表明,初始索力较小的浪风索在较高风速下能有效提高结构抗风能力。

中心城区狭小区域跨河桥梁建造技术及装备研究应用

针对在交通繁忙城市中心狭小区域环境下70 m大跨度钢桥梁的建造施工难题,依托上海北横通道二期工程长寿桥和跨苏州河钢拱桥梁项目,研发改造QMD50T桥面吊悬拼安装工艺装备,实现“梁上运梁、梁上起吊、梁上转体就位”,满足安装精度、施工效率等多项要求,并提出“先梁后拱、后补桥面”方式--跨过路钢拱桥整体安装施工工艺的施工方法,相较于搭设支撑、脚手架等传统方法,能够降低对城市交通的影响,具有很强的实用价值,可为后续类似工程提供经验。