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.

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.

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.

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。

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。

隔板贯通式方钢管混凝土柱-钢蜂窝梁节点抗震性能

目的 研究隔板贯通式方钢管混凝土柱-钢蜂窝梁(DTSCFSTC-SCB)节点的抗震性能,为工程应用提供设计依据。方法 应用有限元分析软件ABAQUS对比DTSCFSTC-SCB节点与隔板贯通式方钢管混凝土柱-钢梁(DTSCFSTC-SB)节点的抗震性能,分析不同参数对其抗震性能的影响。结果 DTSCFSTC-SCB节点的承载力较DTSCFSTC-SB节点的承载力降低10%,延性系数提高6.8%;钢材强度、梁柱线刚度比对其抗震性能影响较大(25%~138%);隔板内(外)伸宽度仅在一定范围内对其延性影响较明显(13%~18%),隔板厚度仅在一定范围内对其承载力影响较明显(7%~8%),开孔率对其最大承载力、耗能能力影响较明显(4%~12%);轴压比、混凝土强度等级、含钢率、孔间距、孔壁距离对其抗震性能影响很小(1%~5%)。结论 该节点具有工程可行性,钢材强度、梁柱线刚度比是影响其抗震性能的主要因素。

宽厚比对足尺方钢管混凝土短柱抗震性能影响的试验研究

开展了6个横截面宽度为800 mm的方钢管混凝土(concrete filled steel tubular,CFST)短柱在恒定轴力和水平往复荷载作用下的加载试验,分析了钢管约束作用(宽厚比B/t=50,B/t=80和B/t=100)对足尺短柱破坏形态、滞回性能、延性性能、刚度退化和耗能能力等抗震性能的影响规律。结果表明:(1)该试验中,所有足尺方钢管混凝土短柱均发生压弯破坏,即在柱底部出现钢管环状鼓曲、核心混凝土压碎行为;(2)方钢管混凝土柱的延性能力随着宽厚比的减少(约束作用提升)并无明显改变,且足尺柱的延性能力明显低于已有试验中的小尺寸柱;(3)宽厚比对足尺方钢管混凝土柱的刚度退化和等效黏滞阻尼系数影响不大;但柱的总耗能随宽厚比的减小而增大;(4)随着宽厚比的减小,钢管约束效应提升,柱压弯承载力有所提高,但提高的幅度明显小于相关规范值。另外,与现有中国、美国、欧洲等设计规范计算结果对比发现,中国规范和欧洲规范的计算结果偏大,美国规范计算结果则较为保守。

拼接外套筒式方钢管柱-H形钢梁框架静力性能研究

为解决传统钢结构梁柱节点焊缝过多、现场施工复杂等问题,提出一种全螺栓现场拼接节点。采用该新型拼接外套筒式方钢管柱-H形钢梁装配式半刚性节点,设计和制作了一个单层单跨门式框架,并完成了梁跨中静力加载试验和有限元分析,考察框架荷载-位移曲线、应变发展规律、破坏模式和承载机制,并通过有限元参数分析,研究带肋角钢厚度及长边尺寸、框架柱距、梁上荷载分布形式、柱轴压比对框架静力性能的影响规律。结果表明:钢框架试件遵循“梁跨中-梁端部-柱及节点区”的变形和破坏顺序。梁跨中应变最大,发生严重屈曲,梁端部及节点区除局部出现轻微变形外,总体应变较小。增设带肋角钢可使梁端塑性铰外移,有效地保护节点区各部件,其上加劲肋的设置是影响框架整体静力性能的关键因素,而带肋角钢厚度及长边尺寸对承载力的提高效果有限。框架柱在高轴压比下,受压侧壁应力较大,建议对该部位进行重点关注并适当采取加强措施。

T型件单边螺栓连接方钢管混凝土柱-钢梁框架抗震性能研究

为研究T型件单边螺栓连接方钢管混凝土柱-钢梁组合框架的抗震性能,设计了一榀由T型件与单边螺栓相连的1:2缩尺的组合框架,并通过拟静力加载试验对框架的承载能力、滞回性能、刚度退化、耗能能力和延性性能进行了分析,并与一榀T型件单边螺栓连接方钢管柱-钢梁框架进行了对比分析,结果表明:两试件滞回曲线均较为饱满,无明显捏缩,方钢管混凝土柱-钢梁组合框架要比方钢管柱-钢梁框架的承载力高,且初始刚度要高出19%,但其耗能能力和延性均有所降低,两试件加载后期承载力下降均较缓慢,且水平位移达到了层间位移角1/30,表明两试件均具有良好的抗震性。

水平力作用下部分填充方钢管混凝土柱的最优填充率分析

在钢管内部分填充混凝土形成的部分填充钢管混凝土柱能提升钢管柱的强度、刚度和抗震性能,适用于桥墩柱和框架中下部柱子。基于验证的精细化有限元分析模型,对部分填充方钢管混凝土柱在轴压和水平荷载共同作用下的受力性能进行了参数分析,主要分析了轴压比(0.1~0.6)、钢管宽厚比(20~50)、钢材强度(Q235~Q690)、混凝土强度(C20~C60)、截面宽度(200~600 mm)和柱子高宽比(4~16)的影响。结果表明:填充率会影响部分填充钢管混凝土柱的破坏模式,随填充率增大,柱子破坏模式从钢管截面破坏转变为柱底部钢管混凝土截面破坏,柱子的强度和刚度提高;混凝土填充率增加到一定程度后柱底钢管混凝土截面形成塑性铰,此时达到最优填充率,继续增加填充率,柱子的强度及延性基本不变;轴压比、宽厚比、钢材强度、混凝土强度、截面宽度和高宽比对最优填充率的影响呈现出规律性变化;建立了部分填充方钢管混凝土柱在轴力和水平力作用下的简化力学模型并提出了其最优填充率的计算方法。

内置约束拉杆横肋波纹钢-钢管混凝土组合柱轴压力学性能研究

为探究约束拉杆对横肋波纹钢-钢管混凝土组合柱轴压力学性能的影响,采用有限元软件ABAQUS数值仿真模拟和轴压试验分析了内置横向拉杆的横肋波纹钢-钢管混凝土组合柱的轴压性能,通过对比分析了内置横向拉杆的数量对横肋波纹钢-钢管混凝土组合柱的荷载-轴向应变曲线、延性、屈服荷载以及核心混凝土约束效应的影响规律。研究表明,内置横向拉杆能够增强对核心混凝土的约束效应,提高横肋波纹钢-钢管混凝土组合柱的轴压承载力和延性。

双向偏压方钢管混凝土柱三面受火耐火性能有限元分析

目的 研究双向偏压方钢管混凝土柱在三面受火作用下的耐火性能,为该类型结构的工程应用提供理论依据。方法 采用ABAQUS软件建立双向偏压方钢管混凝土柱三面受火的热学分析模型与力学分析模型,分析其受力机理及常见参数对其耐火极限的影响。结果 荷载偏心角、荷载比、长细比、截面边长和偏心率是影响构件耐火极限的主要参数,荷载偏心角越大,荷载比越大,长细比越大,截面边长越小,其耐火极限越小。偏心率在0~0.3区间存在明显的极强中心,其耐火极限最大,可比轴压时提高80%以上。结论 在参数分析范围内,提出的耐火极限简化计算公式与有限元计算结果吻合较好。

基于抗震性能的方钢管混凝土柱端加劲肋构造比较与计算

通过构造措施优化方钢管混凝土柱端部加劲肋设计,提高柱抗震性能,是保证工程服役能力的重要方法。本文建立了端部设置不同加劲肋形式的方钢管混凝土柱有限元模型,通过试验验证了有限元模型的可靠性。利用验证后的模型分析加劲肋的形式、高度、宽度对柱体抗震性能的影响,提出柱端设肋试件的水平承载力计算方法。研究结果表明:柱端设肋试件的破坏形态,随着加劲肋高度的增加由肋顶截面破坏转为柱底破坏;在柱端设肋能有效提高试件的承载力和延性;双肋和斜肋对试件承载力的提升相差不大且明显强于单肋;单肋对钢材的利用率依次高于斜肋、双肋;随着加劲肋高度和宽度的增加,试件的极限承载力和延性显著提高;水平承载力计算结果与有限元模拟结果、试验结果吻合较好,达到量化控制水平承载力的目的。