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%

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.

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.

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.

大跨CFST拱桥拱轴线形的综合评分法

为探究500m级钢管混凝土拱桥拱轴线形的合理程度,从钢管混凝土拱桥成桥状态的强度、刚度、稳定性和拱轴线形优化方法的操作复杂性角度,对各最优拱轴线形进行拱轴线形评判指标计算对比,提出一种可用于定量评判钢管混凝土拱桥拱轴线形的优化程度的方法——钢管混凝土拱桥拱轴线形优化综合评分法(CFST-ARO综合评分法)。文中以波司登大桥为工程实例,对经优化后的抛物线、悬链线及三次样条曲线拱轴线形采用综合评分法进行定量评定。结果表明选用3次样条插值函数优化的拱轴线形内力状态优化效果显著,沿跨径方向应力幅度比其他曲线小且均匀,刚度和稳定性都有所提高;以期为同类型拱桥拱轴线形优化评价提供科学参考。

近断层地震作用下大跨CFST拱桥的动力稳定性

为研究大跨度CFST(钢管混凝土)拱桥在近断层地震作用下的动力稳定性能,以主跨132 m的下承式钢管混凝土拱桥为工程背景,以台湾集集地震记录作为横向输入,采用动态增量分析(IDA)方法,对动力失稳临界荷载的确定进行了探讨.为提高IDA的分析效率,采用了高性能数值计算并行处理方法.此外,还讨论了加强IDA曲线簇收敛的问题.结果表明:脉冲型近震可导致非线性极值动力失稳,失稳临界荷载明显降低;采用加权平均加速度峰值作为地震强度指标,能显著改善IDA曲线簇的离散性,有利于揭示近断层地震对钢管混凝土拱桥造成动力失稳的特点.

弹塑性钢阻尼器用于大跨度CFST拱桥的减震控制研究

弹塑性钢阻尼器具有良好的减震效果,但目前的研究和应用主要集中在房建领域。以主跨368m的茅草街大桥为研究对象,进行了弹塑性钢阻尼器用于大跨度钢管混凝土拱桥地震响应的减震控制研究,采用非线性时程分析法进行了阻尼器关键参数的敏感性分析,研究了不同屈服荷载、不同弹性刚度及不同空间布设阻尼器的减震效果,最后重点分析了行波效应对弹塑性钢阻尼器减震效果的影响。结果表明,对于该中承式钢管混凝土系杆拱桥,弹塑性钢阻尼器的减震效果明显;综合考虑各部位的地震响应,在主梁各支承间均匀布设阻尼器为最佳布置方式;考虑行波效应后,阻尼器的减震效果更佳。

Expansion performance and self-stressing behavior of CFST columns considering concrete creep and shrinkage effect

Expansive concrete is used in the steel tube of Concrete-filled steel tubular(CFST)columns to solve the problem of steel-to-concrete debonding.Self-stress is generated between concrete and steel plate due to concrete expansion,which can effectively improve the mechanical performance of CFST columns.Deformation tests were conducted on concrete and CFST columns,respectively.The free deformation of concrete and circumferential deformation of steel tubes were measured and analyzed.A calculation method was proposed to evaluate the hoop strain,self-stress and creep deformation of the CFST columns.The test and calculation results indicate that the proper addition of expansion agent in the internal concrete can keep concrete expansive and generate self-stresses for a long time.The expansion and self-stresses prevent the debonding between the steel tube and the internal concrete.Increasing the dosage of expansive agents and reducing the curing age both increase the expansive deformation and self-stress of CFST columns.Increasing the tube thickness reduces the expansive deformation and increases the initial self-stress of CFST columns.

大跨径钢管混凝土拱桥管内混凝土顶升灌注工艺试验

主拱管内混凝土顶升灌注是钢管混凝土拱桥建设的关键工序和技术难点,大跨钢管混凝土拱桥的管内混凝土方量大、强度高、泵送距离远、灌注时间长,容易出现堵管、爆管现象,国内已有多座桥梁发生该类事故。为降低主拱管内混凝土灌注施工风险,开展了大跨径钢管混凝土拱桥管内混凝土顶升灌注工艺试验研究,探讨了管内混凝土顶升灌注施工过程对混凝土坍落度、扩展度、塑性黏度、运动模式和泵送压力的影响规律。结果表明:管内混凝土经历高压泵送过程后,其坍落度、扩展度和塑性黏度有所降低,对抗压强度影响不明显;在高泵压条件下,混凝土含气量增加,在泵送过程结束时,混凝土含气量降低;混凝土在大直径主拱钢管和小直径泵管内的运动模式存在明显差异,前者运动速度极慢,以管内混凝土自身剪切运动为主,后者运动速度较快,以活塞式整体推移运动为主;管内混凝土运动模式差异导致泵送压力计算方法不同,大直径主拱钢管内混凝土泵送压力以克服重力做功为主,小直径泵管内混凝土的泵送压力以克服管壁摩阻力和自身剪切力为主。通过试验提出了小直径泵管和大直径主拱钢管的管内混凝土泵送压力计算方法,并通过工程实例验证了此方法的适用性。

钢管混凝土拱梁组合桥拱脚构造设计及应力计算分析

浙江省杭州市320国道大桥为单跨161 m钢管混凝土拱梁组合桥,详细介绍了该桥拱脚构造设计特点、施工临时铰构造和拱脚混凝土防裂措施,采用ANSYS软件建立了拱脚实体有限元模型进行局部应力计算分析。分析结果表明,拱脚主拉应力、主压应力基本满足规范要求,局部应力集中区域超出了规范限值,根据应力分析结果对拱脚进行了优化设计,分析成果可为同类桥梁设计提供参考。

新西海桥的振动特性及舒适性评价研究

以日本首座公路钢管混凝土拱桥——新西海桥为对象,进行该桥的自由振动特性分析,采用考虑路面不平整的桥梁与车辆相互作用力学模型,分析了在移动车辆作用下该桥的动力特性,包括冲击系数和舒适度评价。研究结果表明,在移动车辆作用下钢管混凝土拱桥主跨的拱肋和桥面冲击系数都较小,钢管混凝土拱肋的振动小于主桥桥面的振动。从振动舒适性的观点看,采用纵横梁格构桥道体系的新西海桥在车辆荷载作用下拱肋、桥面和人行桥均满足舒适性要求,具有较好的行车性能。

下承式钢管混凝土刚架系杆拱桥吊杆断裂动力分析

以一座下承式钢管混凝土刚架系杆拱桥为研究对象,采用ANSYS/LS-DYNA软件建立有限元模型,通过接触碰撞的方式进行吊杆断裂的模拟,分析吊杆断裂前后拱桥各结构构件受力状态的变化,判断结构可能发生的破坏形态。分析结果表明,吊杆断裂过程中吊杆、钢管混凝土拱肋和桥道系均会受到断索冲击的作用;与断裂吊杆相邻的吊杆受到断索冲击的作用最大,其轴力变化量为初始轴力的3倍以上,需要考虑由于吊杆断裂过程中产生的大于静力响应的动力作用;吊杆断裂对主梁产生的影响远大于拱肋,拱肋内力变化较小;由于横梁两侧与纵梁连接处焊缝强度不足发生破坏可能导致桥道系局部坍塌。

钢管混凝土拱桥肋拱面内极限承载力全过程计算机模拟

采用钢管混凝土统一理论和多线性随动强化模型 ,并引入等效紧箍力 ,研究钢管混凝土肋拱面内极限承载力 ,给出了模拟钢管混凝土肋拱面内受力全过程的物理模型、力学模型、数学模型。通过模拟全过程的位移变化和极限承载力 ,对各个阶段的定性和定量分析 ,并与两个模型试验的比较 ,说明了该模型的适用性和正确性 ,模拟结果表明与试验结果吻合良好 ,并探讨了弹性极限值、屈服极限与极限承载力的比例关系。

脱粘圆形钢管混凝土拱肋的极限荷载试验研究

为了研究钢管混凝土拱桥脱粘后的承载能力情况,将一根圆截面钢管混凝土拱肋成型后置于实验室发生自然脱粘,对自然脱粘后的拱肋进行了四分点处单点非对称加载至破坏的模型试验,采用数值方法和《钢管混凝土拱桥技术规范》(GB 50923-2013)等现行规范的方法分别分析了模型拱肋无脱粘时的极限荷载。试验获得了加载过程脱粘钢管混凝土拱肋模型的应力、变形曲线及面内极限荷载。结果显示:钢管混凝土模型拱肋在自然脱粘情况下,荷载—挠度曲线及荷载—应变曲线仍表现出较大的延性,脱粘后其极限荷载实测值相比无脱粘时的有限元理论计算值略低10%,较按现行几本规范方法的计算值均高40%左右。分析表明,自然脱粘后的钢管混凝土拱肋在外荷载作用变形后仍受到约束,具有良好的弹塑性力学性能及承载能力。研究成果可为钢管混凝土拱桥的进一步研究提供试验数据,并为同类桥梁的发展提供参考。

钢管初应力对钢管砼拱桥承载力影响非线性分析

基于非线性问题的平衡方程和空间梁单元非线性几何方程,推导了一般线弹性关系下计入初应力影响的空间梁单元显式切线刚度矩阵。针对钢管混凝土哑铃型截面的构造特点,提出了组合空间梁单元法,较好解决了哑铃型截面钢管初应力的计算与存储问题,并给出了承载力分析时单元划分的具体方法,编制了专用计算程序,计算结果与试验吻合良好。开展了不同钢管初应力系数、不同截面含钢率和不同跨径对钢管混凝土拱桥承载力的影响分析。结果表明,钢管初应力将使钢管混凝土拱桥的承载力降低,降低幅度与拱肋截面型式有关,承载力最大降低值可超过30%。最后给出了三种考虑钢管初应力影响的常用拱肋截面型式拱桥承载力影响系数实用计算公式。

500m级钢管混凝土拱桥施工控制

为解决500 m级钢管混凝土拱桥施工控制的难题,对既有施工控制方法的局限性进行了分析.根据结构在施工过程中的力学特征,提出了施工控制的可调域法,并对该方法的计算公式进行了推导.基于可调域法的优点和拱肋拼装的要求,给出了吊装线形控制方法.可调域法通过将结构的线形、应力以及索力控制在一定范围内,只在关键施工阶段进行调整,从而减少了调索次数.将该方法应用于波司登大桥,合龙后线形和应力误差均在规范JTG/T F50—2011允许范围内.实践表明,可调域法在500 m级钢管混凝土拱桥施工控制中是可靠的.

设计参数对钢管混凝土系杆拱桥力学性能的影响分析

以中承式钢管混凝土系杆拱桥为计算实例,采用通用软件ANSYS建立了拱桥的有限元计算模型,通过改变其主要设计参数,对该类桥梁在恒载作用下的受力情况进行了对比分析,得出了不同矢跨比、拱轴系数、主拱拱肋含钢率等设计参数对拱桥各控制截面内力、应力、位移变化的影响规律.研究结果表明:改变矢跨比和拱轴系数对系杆拱桥在恒载作用下的内力有较大的影响,且对恒载作用下全截面弯矩的影响比对轴力的影响更为显著;改变钢管的壁厚对于主拱肋各控制截面的轴力、弯矩及应力影响不大.该计算结果可为优化同类桥型的设计提供参考.

飞鸟式钢管混凝土拱桥健康监测系统研究

以东莞水道特大桥为背景,根据该桥桥型及结构受力特点,对该桥进行系统全面的结构受力分析计算,以作为大桥健康监测系统测点布设方案、元器件选型以及安全评估决策分析的依据;叙述了飞鸟式钢管混凝土拱桥健康监测系统构成及各子系统的组成。其中子系统包括:1自动化传感监测系统;2结构安全综合评估子系统。介绍了静态参数监测系统的各传感子系统的部分监测结果,监测数据表明桥梁各监测指标处于正常的变化范围,桥梁总体处于安全、可控的运营状态。

自密实钢管混凝土的研究与应用

采用自密实混凝土作为钢管核心混凝土,针对钢管混凝土的受力特点和施工工艺,进行自密实混凝土材料的选择和配合比优化。为了确保自密实钢管混凝土的顺利施工和硬化后良好的力学、变形性能,进行了自密实钢管混凝土与普通泵送钢管混凝土拱的现场模拟施工对比试验,以及钢管混凝土短柱的轴心受压对比试验。试验结果表明,自密实混凝土作为钢管核心混凝土,其施工性能明显优于普通泵送混凝土,在施工过程中不泌水、不离析,硬化的混凝土能在各截面上均匀分布;自密实钢管混凝土短柱的组合弹性模量、极限承载力和延性以及后期承载能力方面均与普通泵送混凝土短柱相似。在此基础上,成功地将自密实混凝土应用于莆田市一钢管混凝土拱桥工程,应用结果表明,采用自密实混凝土技术,钢管混凝土拱桥施工顺利、快捷,且更好地保证了工程质量,同时混凝土材料造价与普通泵送混凝土基本持平。