Experimental investigation of axially loaded steel fiber reinforced high strength concrete-filled steel tube columns

An experimental study on the compressive behavior of steel fiber reinforced concrete-filled steel tube columns is presented. Specimens were tested to investigate the effects of the concrete strength, the thickness of steel tube and the steel fiber volume fraction on the ultimate strength and the ductility. The experimental results indicate that the addition of steel fibers in concrete can significantly improve the ductility and the energy dissipation capacity of the concrete-filled steel tube columns and delay the local buckling of the steel tube, but has no obvious effect on the failure mode. It has also been found that the addition of steel fibers is a more effective method than using thicker steel tube in enhancing the ductility, and more advantageous in the case of higher strength concrete. An analytical model to estimate the load capacity is proposed for steel tube columns filled with both plain concrete and steel fiber reinforced concrete. The predicted results are in good agreement with the experimental ones obtained in this work and literatures.

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.

Ductility and Ultimate Capacity of Concrete-Filled Lattice Rectangular Steel Tube Columns

A kind of concrete-filled lattice rectangular steel tube(CFLRST)column was put forward.The numerical simulation was modeled to analyze the mechanical characteristic of CFLRST column.By comparing the load-deformation curves from the test results,the rationality and reliability of the finite element model has been confirmed,moreover,the change of the section stiffness and stress in the forcing process and the ultimate bearing capacity of the column were analyzed.Based on the model,the comparison of ultimate bearing capacity and ductility between CFLRST column and reinforced concrete(RC)column were also analyzed.The results of the finite element analysis show that the loading process of CFLRST column consists of elastic stage,yield stage and failure stage.The failure modes are mainly strength failure and failure of elastoplastic instability.CFLRST column has higher bearing capacities in comparison with reinforced concrete columns with the same steel ratio.In addition,the stiffness degeneration of CFLRST column is slower than RC column and CFLRST column has good ductility.

Axial Bearing Capacity of Short FRP Confined Concrete-filled Steel Tubular Columns

The bearing capacity of FRP confined concrete-filled steel tubular （FRP-CFST） columns under axial compression was investigated. This new type of composite column is a concrete-filled steel tube （CFST） confined with fiber-reinforced polymer （FRP） wraps. Totally 11 short column specimens were tested to failure under axial compression. The influences of the type and quantity of FRP, the thickness of steel tube and the concrete strength were studied. It was found that the bearing capacity of short FRP-CFST column was much higher than that of comparable CFST column. Furthermore, the formulas for calculating the bearing capacity of the FRP-CFST columns are proposed. The analytical calculated results agree well with the experimental results.

A simplified model to predict blast response of CFST columns

In order to study the dynamic response of concrete-filled steel tube(CFST) columns against blast loads,a simplified model is established utilizing the equivalent single-degree-of-freedom(SDOF) method,which considers the non-uniform distribution of blast loads on real column and the axial load-bending moment(P-M) interaction of CFST columns.Results of the SDOF analysis compare well with the experimental data reported in open literature and the values from finite element modeling(FEM) using the program LS-DYNA.Further comparisons between the results of SDOF and FEM analysis show that the proposed model is effective to predict the dynamic response of CFST columns with different blast conditions and column details.Also,it is found that the maximum responses of the columns are overestimated when ignoring the non-uniformity of blast loads,and that neglecting the effect of P-M interaction underestimates the maximum response of the columns with large axial load ratio against close range blast.The proposed SDOF model can be used in the design of the blast-loaded CFST columns.

基于结构应力法的钢管混凝土焊接接头疲劳评估

裂纹尖端应力的奇异性导致传统疲劳评估法和部分标准对焊接结构疲劳寿命预测精度不够,影响工程结构可靠性。裂纹扩展是焊趾或焊根所在截面外载荷驱动造成的,基于焊缝处力平衡关系提出结构应力法。该方法将单元节点力转换成线力,并综合考虑不同焊接接头类型、板材厚度和加载模式。运用断裂力学理论将微小复杂裂纹扩展至疲劳失效全过程统一起来,以等效结构应力幅值推导出主S-Nd曲线疲劳评估表达式。采用不同单元仿真试件证明了结构应力法具有网格不敏感力学特征,与试验数据对比,焊缝的薄弱位置和实际疲劳裂纹一致,验证了结构应力法具有较高的疲劳预测精度。钢管混凝土焊接结构验证了结构应力法在疲劳寿命评估时具有有效性和可靠性。

Static behavior of planar intersecting CFST connection in diagrid structure

Intersecting connection plays an important role in the new diagrid structural system for high-rise buildings.To investigate the static behavior of the intersecting connection of concrete-filled steel tubular(CFST)columns,a typical reduced-scale planner connection specimen is tested under monotonic axial compression.The failure modes,force mechanism and bearing capacity of intersecting CFST connections are analyzed further in the follow-up numerical simulation,considering influences of intersecting angle,elliptical plate and ring plate.Test and simulation results prove that,intersecting connection can develop fully plastic deformation and provide sufficient bearing capacity.Parametric analysis indicates that bearing capacity of planar intersecting CFST connection mainly depends on intersecting angle and thickness of elliptical plate,while the ring plate affects that little.Capacity estimation method for planar intersecting CFST connection is proposed basing on the capacity of the critical section which is located near intersecting center for a distance of steel tube radius,and the design suggestions is provided in the end of this paper.

钢管混凝土混合结构设计原理及其在桥梁工程中的应用

钢管混凝土混合结构是由钢管混凝土和钢或混凝土通过优化混合而成的一类高性能结构,成为我国强震区桥梁主体结构的优选形式之一。文章简要论述了两种钢管混凝土混合结构的工作机理和设计原理,即:①桁式钢管混凝土结构,由钢管混凝土弦杆和钢管腹杆混合而成的桁式结构;②钢管混凝土加劲混合结构,由内置的多肢桁式钢管混凝土及其外包的钢筋混凝土混合而成的空心结构。文章还论述了钢管混凝土混合结构在桥梁工程中的应用情况,并展望了该类结构的发展前景。

我国钢管混凝土拱桥应用现状与展望

共收集到截止2015年1月的已建和在建的钢管混凝土拱桥413座(跨径不小于50m)。统计分析表明,钢管混凝土拱桥在我国修建的数量不断增多、跨径不断增大。从行业分布来看,在公路、城市桥梁中的应用仍是主体,在铁路尤其是高速铁路中的应用不断增多。在结构体系方面,上承式、中承式、拱梁组合式、飞鸟式和下承式刚架系杆拱5大类,仍为主要应用的桥型,占总数的85%。在截面形式方面,以圆钢管混凝土为基本单元组成的单圆管、哑铃形和桁式是应用的主流。提篮拱被应用于各种桥型,尤其是大跨度铁路桥。无风撑拱主要应用于120m跨径以下的桥梁,且以斜靠拱和拱梁组合桥为主,截面多采用横向刚度较大的形式。拱肋的材料强度不断地提高,钢管以Q345钢为主,混凝土以C40、C50为主。虽然对桥面系强健性的重视在不断提高,然而强健性好的整体式和具有加劲纵梁的悬吊桥面系的应用还不够普及。钢管拱的架设方法仍以支架法、悬臂法和转体法3种为主,其中悬臂拼装法应用最多,适用跨径最大范围也最广。

钢管混凝土巨型斜交网格筒体结构非线性分析

钢管混凝土巨型斜交网格体系作为筒中筒结构的外筒,使筒体结构具有很大的抗侧刚度,其抗震性能的研究是迫切的需要.本文根据基于性能的抗震设计方法,采用PERFORM-3D软件的纤维模型对超高层钢管混凝土巨型斜交网格筒中筒结构进行了强震作用下的非线性分析,比较了结构在7、8、9度地震作用下的反应。结果表明该结构体系适用于较高抗震设防地区,为该结构体系的应用提供了依据。

极软岩巷道交岔点钢管混凝土支架结构设计与应用

为解决极软岩巷道交岔点支护问题,结合钢管混凝土支架和极软岩巷道围岩的力学特性,分析了钢管混凝土支架控制极软岩巷道变形的机理。对查干淖尔一号井井底车场中3个极软岩巷道交岔点支护问题采用了工程类比法进行分析,结果认为:若能充分发挥钢管混凝土的结构优势,采用"194 mm×10 mm钢管混凝土支架+钢筋网+400 mm厚混凝土喷层"的支护方案可有效控制3个极软岩巷道交岔点的围岩变形。因此,设计了适用于极软岩巷道交岔点的钢管混凝土支架结构形式:极软岩巷道交叉点钢管混凝土支架,采用由支撑架和"C"形异形支架组成的组合结构。提出了查干淖尔煤矿井底车场3个交岔点的支护方案,并进行现场支护试验。现场支护试验证明:巷道交岔点支护2 a后,收敛量小于100 mm,巷道稳定性良好。

新型装配式钢框架结构建筑体系研究与应用

近些年,我国开始大力推进装配式钢结构建筑的应用,国家和地方政府也相继推出多个政策来鼓励和促进其应用和推广,因此,装配式钢结构建筑体系得到了广泛的发展。东南大学、浙江东南网架股份有限公司、北京津西赛博思建筑设计有限公司以及天津大学等研究机构和企业依托"十三五"国家重点研发计划项目"新型框架钢结构体系建筑产业化技术与示范",针对当前装配式钢框架体系建筑在应用中存在的梁柱外露、工业化程度低、施工复杂等问题,提出多腔柱钢框架-支撑、多腔体框架-钢板组合剪力墙、新型框架-核心筒以及钢管混凝土组合异形柱框架结构等新型钢框架结构建筑体系,并对新体系建筑中的关键技术开展深入研究和工程应用,提高了我国装配式钢结构建筑的技术和应用水平,有利地促进了我国建筑工业化的发展。

钢管混凝土平面框架子结构抗连续倒塌精细有限元分析

竖向关键构件失效后,结构的抗倒塌能力主要以失效柱上部钢梁的梁机制和悬链线机制为主。选取"两跨三柱"型钢管混凝土平面框架子结构形式为研究对象,采用精细有限元法细致剖析竖向荷载全过程作用下平面框架的倒塌全过程,分析中柱竖向位移与承载力的全过程曲线特征,研究不同几何和物理参数对框架的抗力曲线的影响规律。结果表明:中柱承载力P-竖向位移Δ曲线分为四个阶段:梁机制阶段、转换机制阶段、悬链线机制阶段、破坏阶段。综合抗力指标和位移延性指标可以看出,钢梁翼缘厚度和钢管含钢率对该类结构的抗连续倒塌影响较为显著,工程实际设计和应用中应予重视。

我国钢管混凝土劲性骨架拱桥发展综述

为了解我国钢管混凝土劲性骨架拱桥的发展动态,明确下一步研究工作的重点,在调查大量该类型桥梁的基础上对其特点及在我国的发展研究现状、设计计算理论、施工方法和跨径的发展进行系统的总结。该桥型具有结构体系转换次数更多、施工周期更长、结构性能更好的特点。目前的研究工作主要集中在收缩徐变效应和施工阶段稳定性两方面。其设计计算方法中应力叠加法更能反映拱桥施工阶段真实的应力状态。钢骨架的安装方法主要分为转体施工法和缆索吊装斜拉扣挂法2种。该桥型增大跨径的方法主要有增强劲性骨架、减轻主拱自重和采用组合施工方法3种。需要进一步开展的工作包括细化桥梁模型试验设计、仿真程序开发及注重结构的耐久性设计。

钢管混凝土-钢板深梁结构抗震性能分析

提出了钢管混凝土-钢板深梁结构,它由钢管混凝土柱、柱间钢板深梁两种构件组成。为深入研究该结构的抗震性能,在典型模型构件试验基础上,用ABAQUS软件对不同钢板深梁布置与间距、不同钢板深梁厚度、不同钢板深梁跨高比的试件进行了数值模拟,模拟中考虑了基础锚固滑移对试件顶部位移的影响。研究表明:随着钢板深梁布置数量的增多和钢板深梁厚度的增大,结构承载力和刚度明显提高,但提高幅度逐渐减慢,而延性有所降低;随着钢板深梁跨高比的增大,结构的刚度和承载力逐步减小,延性逐步提高;合理设计钢板深梁布置位置与间距的试件与整体钢板试件相比,虽承载力和刚度有所降低,但延性和钢板弹塑性耗能能力显著提高,有利于抗震。在满足构造要求下,钢管混凝土-钢板深梁结构具有良好的抗震耗能性能,可用于高层建筑结构抗震设计。

钢管混凝土斜交网格筒结构抗震性能研究

采用PERFORM-3D对钢管混凝土斜交网格筒结构进行静力弹塑性和动力弹塑性时程分析。分析该结构的屈服路径、侧向位移及层间位移角、剪力滞后效应、斜柱损伤及损伤分布模式。结果表明:钢管混凝土斜交网格筒结构传力途径明确,具有较大的抗侧刚度和较好的空间工作性能,且主次节点可以有效地平衡各斜柱内力差,使节点层变形小于其它非节点层;斜交网格筒结构的剪力滞比沿楼层高度由正剪力滞比转变为负剪力滞比,且随着结构的塑性发展,结构首次出现负剪力滞后的位置有所下降;不同类型地震波及不同加速度幅值对斜柱层损伤值影响较大,而对斜柱层损分布模式影响较小。

格构式钢管混凝土风力机塔架的设计

针对风力机塔架高度增加使常用的锥筒式塔架结构的力学性能、经济性、施工性下降的问题,探讨了格构式钢管混凝土风力机塔架的设计方法.以某3 MW风力机工程为例,采用钢管混凝土统一理论和简化空间桁架法设计了符合性能要求的格构式钢管混凝土塔架,并给出了柱肢、腹杆及节点构造.基于ANSYS有限元软件分析了格构式钢管混凝土塔架与锥筒式塔架的力学性能和用钢量,结果表明,三肢柱格构式钢管混凝土塔架的设计方法可行,力学性能优越,经济性较好.

设置阻尼支撑对钢管混凝土拱桥纵桥向减震效果的分析

以主跨为85 m的无推力靠背式下承拱桥为研究对象,旨在供大跨度钢管混凝土拱桥采用消能减震技术进行抗震设计提供参考.在分析动力特性的基础上进行不同强度纵桥向地震荷载作用下的地震反应分析;然后采用消能减震技术在不同部位设置阻尼支撑,并进行相应的地震反应时程分析,确定阻尼支撑的合理设置形式,比较阻尼支撑设置前后的位移、加速度响应时程,探讨阻尼支撑对钢管混凝土拱桥减震效果.研究成果表明,在钢管混凝土拱桥的拱圈与桥面主梁间设置与桥面系成约45°的阻尼支撑有较好的减震效果,能降低位移响应峰值约30%,同时能够降低结构的内力(尤其是弯矩).故可通过消能技术使钢管混凝土拱桥在地震荷载作用下有效控制位移和内力,并使内力分布均匀化,降低拱圈失稳发生的可能性.

考虑几何非线性影响的大跨度拱桥静动力分析

以某大跨度钢管混凝土拱桥为分析对象,应用大型通用软件ANSYS探讨了结构几何非线性对该桥的自振特性及静力受力性能的影响.结果表明:结构几何非线性对该桥的动力性能及结构的内力影响较小,但对结构的变形有一定的影响,在工程设计中应予考虑.

芯钢管连接的钢管混凝土节点偏压承载力

为研究芯钢管连接的钢管混凝土梁柱节点偏心受压承载力的计算方法,应用节点试验和有限元方法对节点承载力进行了分析,表明节点承载力主要由芯钢管混凝土和芯钢管外的环形钢筋混凝土共同承受。根据塑性理论的下限定理,推导出芯钢管混凝土和节点区环形钢筋混凝土的弯矩轴力相关曲线,并对曲线进行了简化。采用叠加原理将芯钢管混凝土和节点区环形混凝土的承载力叠加得到节点偏心受压时极限承载力,给出节点偏于安全的偏压承载力的计算公式,公式中给出考虑芯钢管混凝土受外围环形钢筋混凝土约束后的承载力提高系数k。以35层商住楼钢管混凝土结构实际工程为算例,介绍了节点偏心受压承载力公式的应用方法。