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.

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.

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.

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.

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.

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.

斜撑对方钢管柱-桁架梁节点抗震性能影响试验

为实现施工现场绿色、高效率、高精度的模块化装配式钢结构建筑的建造,分别提出基于柱座式的带斜撑和不带斜撑的装配式方钢管柱-桁架梁节点。共设计4个十字形足尺试件,并对其进行滞回加载试验。分别考察梁破坏和斜撑破坏模态下试件的抗震性能,探究两种破坏模态产生的原因。评估斜撑对节点极限承载力、延性、刚度以及能量耗散能力等抗震性能的影响,分析两种破坏模态下节点的传力机制,并结合破坏模态和受力特性分别给出带斜撑和不带斜撑节点的设计建议。结果表明:不设置斜撑的试件表现出良好的塑性变形和能量耗散能力等抗震性能;斜撑的设置不仅有效地将塑性铰由桁架梁转移到斜撑端部,而且大幅度地提高节点的承载力和刚度,但在斜撑破坏前桁架梁塑性变形能力受限。整个加载过程中,4个试件的柱座与桁架梁之间的连接未出现破坏,且柱子与柱座之间的法兰板未出现明显的滑移现象,该柱座式连接可靠。

薄壁方钢管/竹胶合板组合空芯柱偏心抗压试验研究

对9根薄壁方钢管/竹胶合板组合空芯柱(SBCC)进行了偏心抗压试验,考察了SBCC受压破坏形态,分析了SBCC长细比、偏心距、空心率和净横截面面积对其极限承载力的影响,建立了SBCC极限承载力计算模型.结果表明:SBCC受压破坏形态主要包括柱端部不同基体胶合面开胶和竹胶合板材料开裂破坏、柱身中部受拉侧不同基体胶合面开胶和抗压侧竹胶合板材料压屈破坏、柱整体开胶破坏.SBCC极限承载力随其净横截面面积增大而提高,随其长细比、偏心距和空心率的增大而降低.所建立的SBCC极限承载力计算模型可为其工程应用提供参考.

一种改进型方钢管柱与钢梁连接节点抗震性能研究

该文主要讨论了一种改进型方钢管柱与钢梁连接节点的抗震性能。通过对3个试件进行低周反复荷载试验,研究了是否采用T型件和梁截面高度比两个设计参数对节点域剪切承载力和变形能力的影响。在试验基础上,采用MSC.Marc 2012有限元软件进行了数值模拟分析,有限元模型能够较好地模拟试验试件的各项性能。试验和有限元分析结果表明:改进型高低梁柱异型节点试件应力集中主要发生在T型连接件与梁2的焊接处;虽然两种节点各部分的变形分担率十分接近,但改进型高低梁柱异型节点的剪切承载力和耗能能力分别提高了20%和200%。文末提出了T型连接装置的计算模型和设计方法,为今后实际工程应用提供了参考依据。

配筋空心方钢管高强混凝土偏压短柱有限元分析

目的研究配筋空心方钢管高强混凝土偏压短柱受力性能及延性性能,为配筋空心方钢管混凝土组合柱试验研究提供参考依据。方法利用有限元软件ABAQUS建立了22个配筋空心方钢管高强混凝土偏压短柱模型,对构件的受力全过程及钢材屈服强度、混凝土强度、偏心距和含钢率等参数对其受力性能的影响进行分析。结果配筋空心方钢管高强混凝土偏压短柱受力过程分为弹性阶段、弹塑性阶段、塑性强化阶段、下降阶段。增大钢材强度和含钢率可以使构件的承载力显著提升,延性也越好;提高混凝土抗压强度,构件的承载力增加但延性变差;配普通钢筋可以增加构件的承载力且改善构件的延性。结论配筋空心方钢管高强混凝土偏压短柱充分发挥了各材料的受力特点,在减轻自重的条件下承载力较高且延性较好。

预制方桩用作深基坑混凝土内支撑立柱的设计

为了解决预制方桩用于深基坑工程混凝土内支撑体系竖向承重构件所存在的问题,以盐城某基坑工程为例,介绍了预制方桩与混凝土内支撑结构采用抗剪构件的连接方法,在结构基础底板位置采用刚性止水结合柔性止水的双重防水措施,并对用作混凝土内支撑竖向构件的预制方桩在施工中应注意的问题做出相应的限定.工程监测结果表明:基坑施工过程中,预制方桩立柱最大沉降量为29.62 mm,满足施工要求.采用的这些关键技术措施在实践中取得了良好的效果,可供同类基坑工程参考.

火灾后方钢管混凝土压弯构件滞回性能理论分析

采用数值计算方法,对ISO-834标准火灾作用后方钢管混凝土压弯构件荷载-位移滞回关系曲线进行理论分析,计算结果与实验结果吻合较好,并比较规程BS5400(1979)、LRFD-AISC(1999)、AIJ(1997)、EC4(1994)、GJB4142-2000(2001)、DBJ13-51(2003)在进行火灾后方钢管混凝土压弯构件往复荷载作用下极限承载力计算时的差异。在此基础上,对该类构件荷载-位移关系骨架线进行了参数分析,选用的参数包括含钢率、钢材屈服极限、混凝土抗压强度、轴压比、长细比、受火时间。

配筋空心方钢管高强混凝土轴压中长柱有限元分析

目的 研究配筋空心方钢管高强混凝土轴压中长柱受力性能,改善传统空心钢管混凝土的力学性能,并为该类型柱的设计及试验研究提供依据。方法 基于有限元分析软件ABAQUS,对配筋空心方钢管高强混凝土轴压中长柱的力学性能进行有限元分析,在分析受力全过程的基础上,重点分析长细比、钢管宽厚比,混凝土强度、钢管强度、管桩类型、配筋率等参数对轴压力学性能的影响,并基于统一理论提出承载力计算公式。结果 配筋空心方钢管高强混凝土轴压中长柱各组分之间组合作用良好,内置管柱、增大钢管宽厚比、减小长细比及缩小夹层混凝土强度与管柱混凝土强度差距可以改善构件的延性、提升构件组合作用;笔者提出的修正公式计算结果精确且安全。结论 提高配筋空心方钢管高强混凝土的钢管强度、增大宽厚比、减小夹层混凝土与管柱混凝土强度差距可有效改善空心钢管混凝土脆性破坏,充分发挥构件的性能。

带约束拉杆方钢管/竹胶合板组合柱轴压蠕变性能

对4根带约束拉杆薄壁方钢管/竹胶合板组合空芯柱(SBCCB)试件进行轴压蠕变试验以及蠕变后二次轴压破坏试验,考察试件的轴压蠕变特点、蠕变后受压破坏形态,并分析长期承载对SBCCB试件轴压极限承载力的影响.结果表明:SBCCB试件的轴压蠕变应变随试件长细比的增大而减小、随轴压应力水平增加而增加;不同长细比试件的蠕变应变-时间曲线均包含瞬态蠕变阶段和稳态蠕变阶段,温湿度变化对其局部蠕变有影响;蠕变对试件的轴压承载力、轴向及侧向变形能力有较大影响;基于流变力学理论的Burgers计算模型可较好地预测SBCCB试件的蠕变应变发展.

高强方钢管-混凝土-圆钢管组合短柱轴压性能

为研究高强方钢管-混凝土-圆钢管(HSCS)组合短柱的轴压性能,以环混凝土轴心抗压强度(f ck)、外高强方钢管的抗拉强度、壁厚和宽度、内圆钢管的抗拉强度、壁厚和直径,以及试件的长细比和空心率等为控制参数,共设计27根试件。基于合理的材料本构模型、网格合理性分析和既有试验试件验证分析,确定该模型的预测精度,进而获得各个参数对足尺寸HSCS组合短柱轴压性能的影响规律。结果表明:随宽度、壁厚、内钢管抗拉强度、外钢管抗拉强度和混凝土抗压强度的增加,HSCS组合短柱的轴压承载力显著提高;随试件空心率增加,组合短柱的轴压承载力逐渐减小,建议空心率最佳取值为0.1~0.3。HSCS组合短柱轴压承载力计算表达式具有较高的预测精度,可满足工程实践需要。

薄壁方形钢管/竹胶板组合空芯短柱抗压测试

对带约束拉杆和不带约束拉杆2组各5个薄壁方形钢/竹胶板组合空芯短柱(SBCC)进行轴心抗压试验,考察SBCC受压破坏形态,重点分析横向约束拉杆对试件破坏特征荷载的影响.结果表明:不带约束拉杆试件以竹胶合板基体之间的开胶破坏为主,而带约束拉杆试件主要为柱端材料压折破坏.相对于不带约束拉杆试件,带约束拉杆试件的开裂破坏荷载提高约19.4%,平均极限承载荷载(平均极限压应力)提高约17.2%,轴向压缩变形和压应变均有提高.拉杆约束可抑制SBCC短柱的开胶失效,改变其极限破坏形式而提高其抗压能力.

CFRP加固轴心受压方钢管柱稳定承载力试验研究

结合英国建筑工业研究与情报协会(CIRIA)编写的CFRP(Carbon-Fiber-Reinforced Plastic)加固钢结构设计指导手册《Strengthening metallic structures using externally bonded fiber-reinforced polymers》与我国《钢结构设计规范》(GB 50017—2003),在原轴压钢构件理论计算的基础上,引入稳定承载力修正系数,提出了带有修正系数的CFRP加固轴心受压方钢管柱稳定承载力计算公式,并通过对1个足尺未加固长柱和6个足尺加固长柱进行了轴心受压加载试验研究,分析了CFRP纤维粘贴方向及层数等因素对试件的承载力、破坏模式和延性的影响。利用ANSYS有限元程序建立"壳-弹簧-壳"有限元模型,将有限元计算结果和公式计算值进行了对比。综合考虑各类因素影响,给出利用CFRP布纵向加固时修正系数取为1.05,先环向后纵向或环向加固时修正系数取为0.95。该研究成果为编制国家标准"钢结构加固设计规范"提供了理论和试验依据。

高铁虹桥站钢桁架-钢管混凝土柱节点性能试验研究

最近建设完成的京沪高速铁路上海虹桥站结构中,有一种钢桁架-钢管混凝土柱焊缝连接的新型节点,该节点构造和受力性能极其复杂。本文对该节点进行了1∶4缩尺模型承载力试验研究,介绍了如何实施对该复杂节点加载的试验方法,讨论了节点的受力性能、薄弱环节和破坏模式。试验表明该节点构造设计有效,具有足够的承载力,可达到设计荷载的3倍,并具有良好的塑性变形能力。但是,节点也显示出薄弱坏节,表现为在钢桁架受拉斜腹杆翼缘与节点环板竖向加劲肋的焊接部位出现开裂现象。建议适当增大受拉斜腹杆端部的翼缘弯折曲率半径,平缓腹杆向竖向加劲肋的传力,可使节点性能得到进一步完善。

方钢管柱与桁架梁十字形节点滞回试验研究

提出了一种基于柱座式的装配式方钢管柱-桁架梁连接节点,以实现现场高效率、高精度的层装配式钢结构建筑的建造。该节点主要由柱座、带法兰方钢管柱和桁架梁等组成,其中柱座与桁架梁在工厂完成焊接,现场通过高强度螺栓将柱座与上下柱完成装配。为了研究该新型节点的抗震性能,对3个足尺十字形方钢管柱-桁架梁连接试件进行了滞回加载试验,考察了各试件的破坏模态,评估了梁柱截面尺寸及轴压比对滞回曲线、极限承载力、延性、耗能能力和刚度退化等抗震性能指标的影响规律。试验结果表明:3个试件均表现出良好的抗震性能,各个试件的破坏均始于桁架梁弦杆或腹杆的局部屈曲,结束于桁架梁弦杆或腹杆的开裂;柱壁厚及桁架梁弦杆厚度对试件的承载能力和初始刚度均有显著影响,而轴压比对试件的抗震性能影响较小。加载过程中所有试件的柱座并未发生破坏、法兰板之间无明显滑移,且柱座与桁架梁之间的裂缝未出现撕裂现象,满足“强节点,弱构件”的抗震设计原则。

冷成型轴压方钢管柱破坏模式的数值模拟研究

为准确揭示冷成型轴压方钢管柱的受力全过程,对其极限承载力和破坏模式进行了数值模拟研究,并与试验结果进行了对比。分析中考虑了材料非线性和几何非线性的影响。详细阐述了使用ANSYS进行冷成型轴压方管柱建模时需要注意的问题,并根据模拟结果分析了网格密度、初始缺陷等参数对模拟效果的影响。提出了合理的有限元分析模型、网格划分密度、初始缺陷施加方式等一系列具体措施。数值模拟结果与试验结果吻合良好。给出了实际工程中柱边界条件模拟方法的建议。