Seismic Behavior of Diaphragm-Through Connections of Concrete-Filled Square Steel Tubular Columns and H-Shaped Steel Beams

Based on the introductions of a type of diaphragm-through connection between concrete-filled square steel tubular columns (CFSSTCs) and H-shaped steel beams,a finite element model of the connection is developed and used to investigate the seismic behavior of the connection.The results of the finite element model are validated by a set of cyclic loading tests.The cyclic loading tests and the finite element analyses indicate that the failure mode of the suggested connections is plastic hinge at the beam with inelastic rotation angle exceeding 0.04 rad.The suggested connections have sufficient strength,plastic deformation and energy dissipation capacity to be used in composite moment frames as beam-to-column rigid connections.

Influence of Axial Load Ratio on Shear Behavior of Through-Diaphragm Connections of Concrete-Filled Square Steel Tubular Columns

Nonlinear finite element analysis and parametric studies were carried out to study the influence of axial load ratio on the shear behavior of the through-diaphragm connections of concrete-filled square steel tubular columns. The analysis reveals that smaller axial load ratio can improve the shear bearing capacity and ductility while larger axial load ratio will decrease the shear behavior of the through-diaphragm connections. The parametric studies indicate that the axial load ratio should be limited to less than 0.4 and its influence should be considered in the analysis and design of such connections.

Seismic performance of recycled concrete-filled square steel tube columns

An experimental study on the seismic performance of recycled concrete-filled square steel tube （RCFST） columns is carried out. Six specimens were designed and tested under constant axial compression and cyclic lateral loading. Two parameters, replacement percentage of recycled coarse aggregate （RCA） and axial compression level, were considered in the test. Based on the experimental data, the hysteretic loops, skeleton curves, ductility, energy dissipation capacity and stiffness degradation of RCFST columns were analyzed. The test results indicate that the failure modes of RCFST columns are the local buckling of the steel tube at the bottom of the columns, and the hysteretic loops are full and their shapes are similar to normal CFST columns. Furthermore, the ductility coefficient of all specimens are close to 3.0, and the equivalent viscous damping coefficient corresponding to the ultimate lateral load ranges from 0.323 to 0.360, which demonstrates that RCFST columns exhibit remarkable seismic performance.

Axial Compression Behavior and Analytical Method of L-Shaped Column Composed of Concrete-Filled Square Steel Tubes

Based on the characteristics of an L-shaped column composed of concrete-filled square steel tubes, the axial compression experiment and nonlinear finite element analysis were carried out to study the mechanical property of the L-shaped column. The load-displacement curve for the L-shaped column, the deflection and load-strain curves for the mono columns were obtained by the axial compression experiment. The results show that the L-shaped column exhibits a flexural-torsional buckling failure mode. The numerical simulation by the finite element analysis shows that the bearing capacity and failure mode are in accordance with those of the axial compression experiment and the feasi- bility of the finite element analysis is proved. For the calculation of the bearing capacity of the L-shaped column com- posed of concrete-filled square steel tubes, an analytical method is proposed based on the theory of the elastic stability and spatial truss model. The results of the analytical method are in good agreement with those of the axial compression experiment and the finite element analysis.

Low cyclic fatigue performance of concrete-filled steel tube columns

Eight concrete-filled steel tubular(CFT) columns were tested subjected to cyclic loading under constant axial load. Experimental parameters included axial compression ratio, loading sequences, and strength of concrete and steel. The seismic performance of CFT columns and failure modes were analyzed. The test results show that different axial load ratios and loading sequences have effects on the load carrying capacity, ductility and energy dissipation capacity of CFT columns, as well as the failure modes of the CFT columns. The failure pattern can be categorized into two types: local buckling failure of steel tube in compression zone, and low cycle fatigue tearing rupture failure of steel tube. The seismic behavior was evaluated through the energy index obtained from each cycle.

Behavior of High Strength Concrete Filled Square Steel Tube Stub Columns with Inner CFRP Tube Under Biaxial Eccentric Compression

This paper studies the contribution of CFRP(carbon fiber-reinforced polymer)to the mechanical behavior of high strength concrete-filled square steel tube(HCFST)under biaxial eccentric compression.The new type of composite member is composed of an inner CFRP tube and an outer steel tube with concrete filled in the two tubes.The finite element analysis was made by ABAQUS on the behavior of high strength concrete filled square steel tubular columns with inner CFRP circular tube subjected to bi-axial eccentric loading.The results obtained from the finite element analysis were verified with the experimental results.In addition,the load-deflection curves in the whole process were calculated and analyzed,which can be divided into three segments:Elastic phase,plastic phase,descending phase.Based on the load-deflection curves,the stresses analysis on the core concrete,CFRP tube and steel tube were conducted.The confinement effect of the CFRP tube improves the ductility of HCFST-CFRP stub column.CFRP ratio and eccentricity affect the ultimate bearing capacity of HCFST stub column.Finally,a calculation formula of ultimate bearing capacity was proposed in the paper.

Prediction of Axial Capacity of Concrete-Filled Square Steel Tubes Using Neural Networks

The application of artificial neural network to predict the ultimate bearing capacity of CFST （ concrete-filled square steel tubes） short columns under axial loading is explored. Input parameters consiste of concrete compressive strength, yield strength of steel tube, confinement index, sectional dimension and width-to-thickness ratio. The ultimate bearing capacity is the only output parameter. A multilayer feedforward neural network is used to describe the nonlinear relationships between the input and output variables. Fifty-five experimental data of CFST short columns under axial loading are used to train and test the neural network. A comparison between the neural network model and three parameter models shows that the neural network model possesses good accuracy and could be a practical method for predicting the ultimate strength of axially loaded CFST short columns.

Cyclic behavior of stiffened joints between concrete-filled steel tubular column and steel beam with narrow outer diaphragm and partial joint penetration welds

This paper presented an investigation on a stiffened joint in practical engineering which was between concrete-filled steel tubular column and steel beam with narrow outer diaphragm and partial joint penetration welds. Through the low-frequency cyclic loading test, the cyclic behavior and failure mode of the specimen were investigated. The results of the test indicated the failure mode and bearing capacity of the specimen which were influenced by the axial compression ratio of the concrete-filled tubular column. On the contrary, the inner diaphragm and inner stiffeners had limited impacts on the hysteretic behavior of the joint. There was no hysteresis damage fracture on the narrow outer diaphragm connected to the concrete-filled steel tubular column with partial joint penetration welds. Due to the excellent ductility and energy dissipating capacity, the proposed joint could be applied to the seismic design of high-rise buildings in highly intensive seismic region, but axial compression ratio should be controlled to avoid unfavorable failure modes.

RPC外包方钢管混凝土柱轴压受力性能研究

为了研究活性粉末混凝土(Reactive powder concrete,RPC)外包方钢管混凝土柱的轴压受力性能,以RPC厚度和长细比为参数,对6根构件开展轴压试验研究,探讨该类组合柱的破坏模式、受力机理、套箍效应和承载力。试验结果表明:外层RPC可为内部方钢管混凝土柱提供较强的约束力,在受力后期套箍效应凸显。随着RPC厚度的增加,组合柱的承载力逐渐提高;随着组合柱长细比的增大,虽然其弹性刚度和承载力逐渐降低,但延性改善。采用ABAQUS软件建立RPC外包方钢管混凝土柱的有限元模型,分析RPC强度、RPC厚度、钢管强度等级、含钢率、内部混凝土强度和长细比等参数对组合柱承载力的影响规律,可得方钢管混凝土柱发挥系数的变化幅值为0.78~1.01。在试验研究、有限元参数分析和理论探讨的基础上,借鉴钢管混凝土结构技术规范,提出了RPC外包方钢管混凝土轴压短柱和长柱的承载力简化计算方法,公式计算值与已有数据样本吻合良好。

T型钢连接方钢管柱-H型钢梁节点抗震性能分析

目的为了研究单边螺栓和T型钢连接的方钢管柱-H型钢梁节点的抗震特性,方法采用室内试验和数值模拟分析方法,对1∶2缩尺的边节点进行拟静力试验,并通过ABAQUS有限元软件进行数值模拟,综合分析边节点的滞回特性、承载力、刚度与耗能等力学特性。有限元分析变量为T型钢加肋、梁翼缘狗骨式和梁腹板开圆孔式。结果试验中,节点试件中连接件T型钢参与耗能且其变形最明显,梁、柱构件变形较小。塑性铰主要集中在连接构件T型钢上,T型钢腹板与翼缘交接处出现应力集中状态。试验弹性阶段,节点构件共同抵抗外部作用力。进入塑性阶段,节点损伤逐渐累积至T型钢,使T型钢最终产生塑性破坏而失效。有限元模拟中,T型钢加肋的形式对节点整体承载力影响最大,其中加3号肋的形式使节点承载力的增长量达到最大;梁翼缘狗骨式的形式对节点整体耗能能力影响最大,为44.01%。结论在T型钢上加肋板对节点的承载力和刚度提升较明显,对耗能能力影响不大;梁翼缘狗骨式和梁腹板开圆孔式均能提高节点的耗能能力,节点承载力和刚度基本不变;梁翼缘做狗骨式对节点抗震性能影响最显著。

方形耐候钢管混凝土短柱轴压力学性能研究

为研究方形耐候钢管混凝土短柱的轴压力学性能,首先设计并开展了4根轴压短柱试验研究。进而采用Abaqus有限元软件建立方形耐候钢管混凝土短柱有限元模型并进行数值分析。数值模拟结果表明,轴压短柱直至破坏共经历了3个阶段:弹性段、弹塑性段和破坏段。其破坏模式均为柱中局部屈曲。耐候钢拉伸性能试验特征与低碳钢的力学性能相近,有限元建模采用低碳钢本构关系可准确模拟方形耐候钢管混凝土短柱的轴压力学性能。钢管内焊接拉筋能有效改善钢管对核心混凝土的约束作用,进而提高轴压短柱的极限承载力和延性。最后,方形耐候钢管混凝土短柱轴压力学性能与普通钢管混凝土短柱无异。

新型方钢管混凝土柱轴压力学性能试验研究

研发了一种旨在提升核心混凝土约束作用和整体承载能力的新型方钢管混凝土柱,并以抗剪钉、拉板、加劲肋等不同构造为试验参数,系统进行了多个试件的轴压试验。试验结果表明:新型方钢管混凝土柱的破坏模式为屈曲破坏,方钢管破坏区域产生局部鼓曲,最终混凝土压溃。采用ABAQUS有限元分析软件建立了4根新型方钢管混凝土柱的数值分析模型,对其在轴向压力作用下的承载力进行精细化模拟,结果表明:有限元分析得到的柱破坏形态和荷载-位移关系曲线均与试验结果吻合较好。建立了该新型方钢管混凝土柱的极限承载力表达式,理论分析结果精确度较好。对相关影响参数进行分析可知,设置加劲肋可显著提升新型方钢管混凝土柱的轴压承载力,而设置拉板和抗剪钉与否对其轴压承载力影响不显著。

花瓣形钢管混凝土柱轴压受力机理和承载力研究

花瓣形钢管混凝土柱具有造型美观的优点,为具体研究其受力机理和承载力,定义了其截面组成,提出了截面偏移比和截面对称系数以反映花瓣形截面性质,提出在花瓣柱中设置十字形加劲肋以增强其组合效应。基于某工程中墩柱和有限元模型,研究了花瓣形钢管混凝土短柱在轴压荷载作用下的受力机理,分析了加劲肋厚度、混凝土强度、钢材强度、加劲肋开孔直径和间距等参数对轴压性能的影响,研究了加劲肋厚度与钢管壁厚的匹配关系。根据理论分析和大量有限元参数分析结果,建议了加劲肋厚度与钢管壁厚之比和钢管名义径厚比的取值范围,提出了花瓣形钢管混凝土短柱的轴压承载力计算式。

柱端带肋方钢管混凝土柱抗震耗能分析

方钢管混凝土柱在高层及超高层中得到了广泛应用,但存在钢管对混凝土约束较弱与柱端部局部屈曲等问题,有必要采取构造措施以提高柱的抗震性能。通过建立端部带肋方钢管混凝土柱的三维实体精细有限元模型并与拟静力试验结果验证,有限元结果与试验结果吻合良好,之后建立多个足尺模型进行参数分析,分析了柱端设肋对钢管水平鼓曲与竖向位移、钢管与混凝土的应力-应变、塑性耗能的影响,探讨了不同肋高下柱的塑性耗能分配机制。结果表明:柱端设置加劲肋可显著减少柱的水平鼓曲和竖向位移,提高柱的峰值承载力和延性,减小钢管与混凝土的压应变并提高压应力,增大柱的总塑性耗能值,延缓柱的破坏;轴压比为0.5、0.8时,当肋高分别达到1000mm、1500mm,再增大肋高对柱的塑性耗能影响较小。研究结论可为实际工程中柱端带肋方钢管混凝土柱的设计与加固构造措施提供参考与依据。

L形多腔方钢管混凝土柱的抗火性能研究

为研究L形多腔方钢管混凝土柱的抗火性能,建立了42个不同荷载比、钢材屈服强度、柱肢宽度和混凝土抗压强度的有限元模型,并进行火灾模拟分析。结果表明:模型的测点温度和轴向位移的模拟值与试验值误差较小,模型具有可靠性,可用于异形多腔钢管混凝土柱的抗火性能模拟;荷载比的减小、钢材强度的减小、混凝土强度的增大和柱肢宽度的增大有利于构件耐火极限的提高;提出了L形多腔方钢管混凝土柱的耐火极限计算式并验证了其准确性,为此类构件在装配式住宅的工程应用中提供了抗火设计依据。

方钢管混凝土柱与钢梁连接的设计方法

在试验研究和理论分析的基础上 ,提出了方钢管混凝土柱与钢梁连接节点的设计及构造建议 ,并对试验结果和理论公式的计算结果进行了对比 .这一设计方法已被国家有关技术规程所采纳 .

钢管混凝土加强环式节点的试验研究

钢管混凝土柱由于其优越的力学性能而在工程中得到了广泛的应用 ,但是其节点的研究显得还不够完整和充分 .本文中研究了 2个钢管混凝土加强环式梁柱节点的力学行为 ,分析了梁、钢管壁和加强环的应变分布规律 .试件均采用钢梁 ,并采用构造不同的环间加劲肋 .试验结果表明 ,钢管混凝土加强环式节点力学性能良好 ,节点刚度大 ;环间加劲肋的构造对节点的受力性能影响不大 ;加劲肋可以看作加强环梁的弹性支座 。

装配式方钢管柱桁架梁节点单调加载试验研究

提出一种新型的装配式方钢管柱桁架梁节点,对4个足尺方钢管柱桁架梁节点试件进行单调加载试验研究。主要研究连接板厚度以及桁架梁的腹杆形式对节点的承载能力和破坏形态的影响,详细观察节点试件在单调荷载作用下的受力过程,分析节点的刚度、强度以及延性性能等指标,同时结合现有规范对节点的延性进行评价。研究结果表明,节点连接板的厚度对节点的承载力和刚度影响较大,桁架梁的腹杆形式对节点的承载力影响较大,此节点形式具有较好的延性性能,可满足规范中的抗震设计要求,可以在实际工程中应用和推广。

方钢管混凝土柱与钢梁的外肋环板节点抗震性能试验研究

为研究外肋环板节点的抗震性能,本文对3个十字型足尺试件进行了低周反复循环加载试验,分析了各试件的破坏过程及特征,然后根据实测的滞回曲线对节点的承载力、延性、耗能能力、强度退化、刚度退化等抗震性能指标进行了详细的比较分析。研究结果表明,外肋环板节点构造措施简单合理,具有较好的抗震性能。通过空钢管试件和填充混凝土试件的对比分析,表明在钢管中填充混凝土有利于改善节点的抗震性能。

方钢管混凝土柱-H型钢梁外肋环板节点研究

在分析方钢管混凝土柱-H型钢梁框架3种刚接节点的构造形式和特点的基础上,提出了一种新型刚接节点———外肋环板节点。以外肋环板节点梁翼缘受拉模型为对象,分析了节点的受力传力机理,并基于屈服线理论,推导出了梁翼缘受拉模型的屈服承载力计算公式,为这种新型节点今后的研究和工程应用提供了依据。