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.

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.

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.

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.

An Experimental Study on the Behavior of Square Concrete-Filled High Strength Steel Tube Columns

The paper presents an experimental study on the behavior of square concrete-filled high strength steel tube columns until failure.Four specimens were tested to investigate the effect of high strength steel and plain strength concrete on the load carrying capacity of the square concrete-filled steel tube columns.The effect of the concrete which filled in the steel tube was also investigated.Also,the effect of high strength steel and the presence of concrete were also investigated.The main parameters in the tests were:(1) the ultimate strength of steel (800 Mpa),(2) the presence of concrete in steel tube (hollow steel tube and concrete-filled steel tube),and (3) slender ratio.The main objectives of these tests were three-step:(1) to describe a series of tests on composite columns,(2) to analyze the influence of several parameters,and (3) to compare the accuracy of the predictions by using the specifications in the code (AISC-LRFD,EC4 and AIJ etc.) for the design of high-strength composite columns.Experimental results indicate that the ultimate strength of steel and presence of concrete had significant influence on both the axial compressive load capacity and the ductile of the square steel tube.

单向载荷下建筑用方钢管柱螺栓连接节点的抗冲击性能

用高强螺栓与Q345B钢制备方钢管柱螺栓连接节点试件,分别施加80、120、160 kN的预紧力,制成3种不同预紧力的连接节点试件。通过落锤冲击试验对试件施加单向载荷,并进行承载力与耗能测试,分析单向载荷下方钢管柱螺栓连接节点的抗冲击性能。结果表明:当单向载荷冲击速度较大时,试件的冲击力、位移均增大;其中,施加160 kN预紧力的试件的冲击力与位移始终较低,且冲击持续时间较短,具有良好的抗冲击效果;当试件经单向载荷冲击后,3组试件的极限承载力均有所降低,但施加160 kN预紧力的试件的承载力与耗能较高。因此得出,施加160 kN预紧力的方钢管柱螺栓连接节点抗冲击性能最优,更适用于高层建筑钢结构。

方钢管混凝土桁架结构优化的拟满内力遗传算法

为解决离散变量方钢管混凝土桁架的结构优化问题,以桁架杆件最低总造价为目标函数,采用拟满内力遗传算法对杆件截面进行结构尺寸优化.拟满内力遗传算法引入拟满内力算法作为遗传算子,并将部分初始种群由拟满内力算法产生以增加种群多样性.对传统遗传算法罚函数进行改进,以增强算法的寻优效率.通过两个算例的对比分析,结果表明运用拟满内力遗传算法进行方钢管混凝土桁架结构优化,相对于拟满内力算法和传统遗传算法其造价分别降低了15%、15%、45%、53%.拟满内力遗传算法进行方钢管混凝土桁架结构优化的是有效、可行的.

广州白云国际会议中心国际会堂结构设计和施工重难点

采用YJK和ETABS对广州白云国际会议中心国际会堂结构进行弹性分析,采用Perform-3D进行罕遇地震作用下的整体结构弹塑性动力分析,并通过采取针对性的加强措施,改善了结构受力,提高了结构抗震性能,达到了预设的抗震性能目标。对大跨度钢结构构件进行方案选型,提出了大跨度钢结构桁架局部构件后装施工控制法和大悬挑钢结构桁架构件局部弯矩释放法,可以有效地减小结构构件局部受力,更加经济合理。对主会场大跨度楼盖进行竖向舒适度分析,结果表明竖向振动加速度满足规范要求,人群激励模式起控制性作用。通过采用合理的结构方案,以及与建筑专业的密切配合,很好地实现了建筑功能及建筑造型,以及项目快速建造的要求。

Experimental Study on Seismic Behavior ofSeismic-damaged Lateral Joints in CompositeFrame Consisting of CFSST Columns and SteelBeams Strengthened with Enclosed ReinforcedConcrete

A new composite strengthening method of seismic-damaged lateral joints in composite frame consisting of Concrete-Filled SquareSteel Tubes （CFSST） columns and steel beams strengthened with enclosed Reinforced Concrete （RC） at the ends of columns andwelding steel plates at the ends of beams was presented. Based on the current design specifications, one half scaled models of 4lateral joints in composite frame consisting of CFSST columns and steel beams were designed and manufactured. One model wasoriginal control specimen, one was strengthened by enclosed RC, and the others were strengthened after pre-damage. The destructiontests under lateral cyclic load on the models were carried. The effectiveness of seismic-damaged joints strengthened with enclosedRC and the reinforcement effect on different levels of seismic damage were studied. The test results show that seismic- damagedjoints in composite frame consisting of CFSST columns and steel beams strengthened with enclosed RC meets the strongcolumn-weak beam joints requirement of seismic design, and the failure modes are of all joints are the bending failure of steel beam.The reinforcement with enclosed RC has a significant on increasing the ultimate capacity and the seismic behaviors of joints. Thestudy indicated the rehabilitated joints recover the level of their original seismic performances before seismic damage in a certainextent damage level. Based on the test data, namely the ultimate capacity, limit displacement, ductility, the energy consumptioncoefficient, limit displacementthe strengthening method of seismic-damaged joints by strengthened with enclosed RC is an effectivemethod for seismic strengthening.

高铁站站前广场大跨度钢结构吊装施工技术分析

在钢结构施工过程中,吊装是核心环节,设备选型及吊装计算等对施工安全至关重要,要结合施工现场实际情况制订合理的施工方案,为钢结构吊装施工质量和安全提供保障。文章以贵安高铁站东广场项目为例,在顶板混凝土施工完成后,结合施工条件,选用相应的施工方案,为解决类似工程问题提供了参考。

基于硅钢叠铁心方形铁心轭结构能效变压器的设计和结构研究

变压器制造材料主要由铁心、绕组、变压器油以及钢板等组成。现有变压器制造企业的硅钢叠铁心变压器的铁心柱和铁心轭均采用类圆形(圆形、长圆形、椭圆形)结构,制造材料成本较高。因此,提出一种基于硅钢叠铁心方形铁心轭结构能效变压器的设计和结构研究方案,即增大铁心轭的截面,减小铁心柱的截面,减少绕组所用铜线的长度,减小绕组所用铜线的截面积,达到在变压器各种性能指标及制造企业制造工艺相同的情况下降低制造企业变压器制造材料成本的目的。在不改变绕组结构的基础上,通过硅钢叠铁心方形铁心轭结构能效变压器的结构研究,大幅增强变压器的抗轴向短路能力,以增强变压器制造企业的市场竞争力,提升变压器产品的运行稳定性。

矩形钢管混凝土柱的超声波检测试验及计算公式研究

分析了目前用于矩形钢管混凝土柱计算的三种理论,依据理论分析和钢管混凝土超声波检测的试验数据,提出了矩形钢管混凝土柱计算中叠加原理的应用论据。基于日本矩形钢管混凝土柱计算的叠加理论,按照计算简洁、概念明确和安全可靠的原则,确定了矩形钢管混凝土柱的计算公式,并用于天津市钢结构住宅设计规程(DB29—57—2003)。

方钢管混凝土柱抗剪性能试验研究

研究方钢管混凝土柱在弯剪和压弯剪受力状态下的力学性能,进行了6个足尺方钢管混凝土柱的抗剪承载力试验,以剪跨比和轴压比作为主要参数,讨论试件的破坏形态、剪力-位移曲线等试验结果,分析剪跨比和轴压比等因素对构件抗剪承载力的影响,并对构件的抗剪性能进行非线性有限元分析.根据有限元计算结果,拟合推导出考虑轴压力影响的方钢管混凝土柱弯剪试件抗剪承载力与剪跨比关系的经验公式,公式计算结果与试验结果吻合较好,稍偏于安全,可供工程实践参考.

厚壁方矩形管冷弯效应对比分析

为了对厚壁型钢管的冷弯工艺改进、性能分析、结构强度设计和数值模拟结果的验证提供重要依据,进行了冷弯厚壁钢管上截取的平板件、弯角件、母材和相应方、矩形截面短柱的力学性能试验研究,获得了短柱全截面屈服强度相对于母材强度的提高值。分别运用北美等国厚壁冷弯型钢规范、国内薄壁冷弯型钢规范以及相关文献中的修正规范,对我国厚壁冷弯方矩形型钢管全截面强度进行设计和对比分析。结果表明:因冷弯工艺不同,国外公式计算的结果高于国内短柱实测值,国内厚壁冷弯型钢的强度设计不能照搬现有的国外厚壁冷弯型钢设计规范;国内薄壁公式能否适用要视型钢的冷作硬化效应程度决定;原料的强屈比和冷弯应变程度越大,则冷作硬化效应越大;焊接热使板件受到低温"退火"的作用不可忽略,其常常导致竖直配辊冷弯厚壁矩形型钢时,两竖直侧平板件强度低于母材。

钢-混凝土组合框架结构体系抗震性能研究

为了研究钢-混凝土组合框架结构体系的抗震性能,本文分别建立了组合梁-方钢管混凝土柱框架结构(CB-CFST)、钢梁-方钢管混凝土柱框架结构(SB-CFST)、组合梁-等刚度RC柱框架结构(CB-ETRC)、钢梁-等刚度RC柱框架结构(SB-ETRC)和RC框架的结构模型.并对该5种结构进行了模态分析、多遇地震下的反应谱分析、弹性时程分析和罕遇地震下的弹塑性时程分析.结果表明:与钢梁-方钢管混凝土柱框架结构相比,组合梁-方钢管混凝土柱框架结构整体刚度得到提高,自振周期变短,结构位移反应总体变小.与组合梁-RC柱框架结构相比,在罕遇地震下,RC柱在通常配筋下已不能满足'大震不倒'的要求,增大柱截面配筋后,柱端仍出现塑性铰.

方钢管混凝土轴压短柱的力学性能研究

为研究方钢管混凝土轴压短柱力学性能,采用试验和ABAQUS有限元模拟分析相结合的方法,得到方钢管混凝土短柱实用承载力计算公式.对3根方钢管混凝土轴压短柱试件进行试验研究,并应用ABAQUS软件对其进行三维实体有限元分析,模拟结果与试验结果吻合较好.首先,在有限元模型得到验证的基础上,基于有限元法进行大量参数分析,确定方钢管混凝土轴压短柱极限状态时方钢管平均纵向应力与屈服强度的比值;其次,根据有限元模型得出核心混凝土处于极限状态时的应力云图,并将其简化为不受方钢管约束的非加强区核心混凝土和受方钢管均匀约束的加强区核心混凝土,确定两者的面积比;最后,在前两者的基础上根据极限平衡理论,提出一种新的方钢管混凝土轴压短柱承载力实用计算公式,并将该公式和现有公式计算结果以及已有的98组方钢管混凝土轴压短柱有效试验结果进行对比.结果表明,该公式计算结果与试验结果吻合最好.

方形薄壁钢管轻骨料混凝土短柱的承载力

采用双剪统一强度理论,综合考虑方形薄壁钢管的局部屈曲效应以及轻骨料混凝土与普通混凝土多轴强度准则差异的影响,推导出了方形薄壁钢管轻骨料混凝土轴压短柱的极限承载力计算公式,同时分析了拉压比、材料强度参数、宽厚比和混凝土强度对极限承载力的影响。结果表明:该计算结果与文献试验结果吻合良好,验证了公式的合理性;该结果为方形薄壁钢管轻骨料混凝土轴压短柱的承载力分析计算提供了理论依据,具有工程参考价值。

基于高频压电阻抗谱的钢框架损伤识别研究

采用压电阻抗技术(EMI)对三层钢框架进行了损伤模拟实验,通过拧松钢框架节点的螺栓来模拟损伤,测试了钢框架在不同损伤程度下的电导纳值.并采用均方差(Root Mean Square Deviation,RMSD)、协方差(Covariance)和均方根(Root Mean Square,RMS)作为损伤程度参数指标对实验数据进行了分析,验证了利用压电阻抗技术进行结构健康检测的有效性,表明RMSD指标对反映结构损伤程度更准确可靠.