Numerical Analysis of Cold-Formed Thin-Walled Steel Short Columns with Pitting Corrosion during Bridge Construction

Pitting corrosion is harmful during bridge construction,which will lead to uneven roughness of steel surfaces and reduce the thickness of steel.Hence,the effect of pitting corrosion on the mechanical properties of cold-formed thin-walled steel stub columns is studied,and the empirical formulas are established through regression fitting to predict the ultimate load of web and flange under pitting corrosion.In detail,the failure modes and load-displacement curves of specimens with different locations,area ratios,and depths are obtained through a large number of non-linear finite element analysis.As for the specimens with pitting corrosion on the web,all the specimens are subject to local buckling failure,and the failure mode will not change with pitting corrosion,but the failure location will change with pitting corrosion location;the size,location,and area ratio of pitting corrosion have little influence on the ultimate load of cold-formed thin-walled steel short columns,but the loss rate of pitting corrosion section area has a greater impact on the ultimate bearing capacity.As for the specimen with flange pitting corrosion,the location and area ratio of pitting corrosion have less influence on the ultimate load of cold-formed thin-walled steel short columns,and the section area loss rate has greater influence on the ultimate bearing capacity;the impact of web pitting corrosion on the ultimate load is greater than that of flange pitting corrosion under the same condition of pitting corrosion section area.The prediction formulas of limit load which are suitable for pitting corrosion of web and flange are established,which can provide a reference for performance evaluation of corroded cold-formed thin-walled steel.

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.

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.

Experimental study on the seismic behavior of high strength concrete fi lled double-tube columns

To study the seismic behavior of high strength concrete fi lled double-tube(CFDT) columns,each consisting of an external square steel tube and an internal circular steel tube,quasi-static tests on eight CFDT column specimens were conducted.The test variables included the width-to-thickness ratio(β1) and the area ratio(β2) of the square steel tube,the wall thickness of the circular steel tube,and the axial force(or the axial force ratio) applied to the CFDT columns.The test results indicate that for CFDT columns with a square steel tube with β1 of 50.1 and 24.5,local buckling of the specimen was found at a drift ratio of 1/150 and 1/50,respectively.The lateral force-displacement hysteretic loops of all specimens were plump and stable.Reducing the width-to-thickness ratio of the square steel tube,increasing its area ratio,or increasing the wall thickness of the internal circular steel tube,led to an increased fl exural strength and deformation capacity of the specimens.Increasing the design value of the axial force ratio from 0.8 to 1.0 may increase the fl exural strength of the specimens,while it may also decrease the ultimate deformation capacity of the specimen with β1 of 50.1.

新型波纹管连接方钢管混凝土拼接柱抗震性能试验研究

为研究一种新型波纹管连接方钢管混凝土拼接柱的抗震性能,以不同节点配筋率、不同节点锚固长度和轴压比为主要研究变量,对1个整浇柱和4个装配柱进行低周往复加载试验。研究分析了整浇柱与装配柱在破坏模式、滞回性能、位移延性等方面的抗震性能差异。结果表明:装配柱与整浇柱破坏模式类似,采用不同节点构造的装配柱与整浇柱在滞回曲线、骨架特性和刚度退化等方面差异不大,装配柱的耗能性能优于整浇柱。各装配柱极限位移角为1/16.7~1/25,满足规范设计要求。在较大轴压比下,装配柱的承载力提升,延性降低。在较大位移角下,装配柱节点抗震性能受焊缝质量的影响较大,建议实际工程中加强焊接质量管理,以保证构件具有足够的变形能力。

轴压比对波纹侧板-方钢管混凝土柱抗震性能的影响研究

为研究轴压比对波纹侧板-方钢管混凝土柱抗震性能的影响,使用ABAQUS软件建立了组合结构柱的有限元模型,通过破坏形态和滞回曲线等对模型的准确性进行了验证,运用参数模型讨论了不同轴压比对试件的破坏形态、滞回曲线、骨架曲线、压弯承载力和延性系数的影响。结果表明,随着轴压比增大,方钢管的高应力高度逐渐升高,波纹板的应力由水平分布变化为斜向分布;提高轴压比会使试件的压弯承载力和延性系数呈先升高后降低的趋势,建议轴压比不应超过0.30,满足规范中对延性系数的要求并在一定程度上提高结构的压弯承载力。通过合理控制轴压比,可以提升波纹侧板-方钢管混凝土柱抗震性,确保其在实际应用中的安全性和稳定性。

方钢管螺旋筋约束自密实高强混凝土柱抗震性能试验研究

为研究方钢管螺旋筋约束自密实高强混凝土柱的抗震性能,以轴压比、剪跨比、有无配制螺旋筋以及螺旋筋间距作为设计参数,进行了7个试件的低周反复加载试验,获取了各试件的滞回曲线以及应变分布。试验结果表明:试件破坏特征主要为方钢管柱脚区域出现明显鼓曲形成塑性铰区域;随轴压比的提高,试件抗剪承载力、环线刚度和耗能能力均有提升,剪跨比对试件抗震性能的影响规律不明显。配制螺旋筋对峰值承载力和刚度的影响较小,而对试件延性及耗能的提升明显,与无配筋试件相比试件延性平均提升了15.4%,耗能平均提升了114.9%。螺旋筋间距越密对试件抗震性能提升效果更优;适当增大轴压比,控制剪跨比在5以内以及增设螺旋筋对提升其承载能力和变形能力有积极作用。

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。

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。

方钢管再生混凝土中长柱的抗震损伤分析

方钢管再生混凝土柱可以充分发挥钢材与再生混凝土的材料性能优势,不仅具有良好的力学性能和抗震性能,而且还科学地处理了建筑垃圾。为了探索方钢管再生混凝土中长柱在低周往复荷载作用下的损伤演化规律,文章根据6根柱的低周往复加载试验,研究钢管壁厚、轴压比和长细比3个参数对试件抗震损伤的影响,分析各试件的破坏形态和刚度退化规律,且采用4种损伤分析模型对各试件进行损伤分析研究。基于不同损伤模型的计算结果,给出方钢管再生混凝土中长柱对应不同抗震性能水准的量化损伤指标。研究结果表明:对于不同变化参数下的方钢管再生混凝土中长柱试件,不同损伤分析模型计算所得各个试件的损伤指标值都呈单调增加趋势;随着轴压比的增加,试件的承载力有所提高,变形能力减小,累积损伤加重;随着长细比的增加,试件的承载力降低,变形能力提高,累积损伤减轻;随着钢管壁厚的增加,试件的承载力和变形能力均提高,累积损伤有所减轻。

柱中设缝的方钢管约束型钢混凝土中长柱受压性能研究

钢管约束混凝土柱的钢管通常在柱端设缝以使其不直接承受荷载。该文主要对两种设缝模式的方钢管约束型钢混凝土柱(仅柱两端设缝、柱两端和柱中均设缝)的受力性能进行分析对比。以钢管宽厚比、荷载偏心率为主要变化参数,对柱中设缝的方钢管约束型钢混凝土中长柱进行了受压力学性能试验。分析对比了各组试件的破坏模式、承载能力及钢管应力发展规律,结果表明:设缝模式对试件破坏形态无明显影响,柱中设缝试件的轴压承载力略有提高,而偏压承载力呈降低趋势。采用精细化的有限元模型进行了参数分析,依据试验及有限元结果,提出用于计算构件弯矩增大效应的刚度折减系数公式,进而建立柱中设缝构件偏压作用下的承载力计算方法。

方中空不锈钢管混凝土短柱轴压承载力性能

为促进方中空不锈钢管混凝土构件在土木工程中的应用,以不锈钢外管厚度和混凝土强度为变量的6组试件为研究对象,首先,进行轴压试验,得到了不同试件在轴压荷载作用下的破坏模式、荷载-位移曲线、荷载-应变曲线,并进一步分析了不锈钢方管宽厚比、核心混凝土强度以及不锈钢方管约束效应系数对方中空不锈钢管混凝土短柱极限承载力的影响;然后,初步讨论了倒角对强度和延性的影响,提出了避免内管先于外管屈曲的最小厚度计算方法;最后,基于试验结果以及已有文献数据,采用拟合方法推导了方中空不锈钢管混凝土短柱的抗压承载力计算式,并与已有文献的简化模型及国外主要规范的计算结果进行对比.研究结果表明:试件宽厚比由34.9降至20.9,极限承载力的提升率平均为98.5%,核心混凝土强度由C40提升至C60时,试件极限承载力的提升率平均为7.3%;短柱的轴压极限承载力随约束效应系数近似呈线性增加,约束效应系数ξ越大,短柱的承载力越高;本文得到的计算式可以较好地预测方中空不锈钢管混凝土短柱的轴压承载力.

绿色纤维钢管混凝土轴压性能有限元分析

为研究绿色纤维对方钢管混凝土短柱受力性能的影响,通过ABAQUS对不同纤维体积掺量钢管混凝土短柱进行数值模拟分析,共设计3组试件,纤维掺入量分别为0%、1%、1.5%,通过观察不同掺量下构件的变形图以及荷载-位移曲线来研究绿色纤维对其构件力学性能的影响。结果表明绿色纤维对构件的横向变形影响较大,随着掺入量的增加,绿色纤维对构件的承载能力有明显提高,改善了构件的脆性和延性,并提高了整体构件的力学性能。

内嵌轻质墙板L形方钢管混凝土组合柱框架结构抗震性能试验与数值模拟

针对内嵌轻质墙板双钢板连接L形方钢管混凝土组合柱(LCFST柱)框架结构的抗震性能,设计并制作了未安装墙板的LCFST柱框架试件SJ-1和内嵌轻质墙板的LCFST柱框架试件SJ-2进行低周反复荷载试验,并通过有限元软件对内嵌墙板厚度、墙板强度进行参数化分析.试验结果表明:两框架结构属于“强柱弱梁”的破坏模式;SJ-2中墙板破坏多出现墙板顶端和角部,内嵌墙板可在一定程度上延缓主体框架的破坏;SJ-1和SJ-2均具有良好的耗能能力、延性和变形能力;SJ-2较SJ-1,正、负向弹性刚度、极限承载力均有明显提高,耗能能力比SJ-1略有增加.参数分析表明:增大墙板的厚度或强度,整体结构初始刚度的提升很小,但其峰值荷载的提升较为明显;其中墙板厚度由100 mm增至200 mm,墙板对峰值荷载的贡献率从22.76%提升至30.70%;墙板强度由2.5 MPa增至7.5 MPa,墙板对主体结构峰值荷载的贡献率从23.68%提升至34.52%.

方形截面不锈钢管混凝土短柱轴压性能有限元研究

不锈钢管混凝土(CFSST)结构在工程的应用愈发广泛,但目前对其轴压性能的研究较少。该文利用ABAQUS创建方形不锈钢管混凝土短柱(CFSSST)模型,并利用收集到试验结果对其进行验证。采用已被验证的模型进行参数分析,研究截面宽厚比和混凝土强度对其轴心受压性能的影响,并将参数分析轴压承载力结果与GB 50936—2014《钢管混凝土结构技术规范》、欧洲规范EN 1994-1-1和美国钢结构规范AISC 360-16中钢管混凝土(CFST)短柱轴压承载力的计算值进行对比,结果表明:规范的计算值偏于保守。最后,基于GB 50936—2014《钢管混凝土结构技术规范》提出适用于CFSSST短柱轴压承载力的计算公式,收集到的试验结果与计算值吻合良好。

方钢管再生混凝土叠合柱轴压性能有限元非线性分析

为研究方钢管再生混凝土叠合柱的轴压性能与非线性力学性能,在叠合柱轴压性能试验研究基础上,利用ABAQUS软件建立了叠合柱精细化模型,对其轴压性能进行非线性数值模型分析研究。并在此基础上进一步扩展分析了再生混凝土强度等级、拉结筋间距、箍筋间距、方钢管壁厚及长细比对叠合柱轴压性能的影响,获得了叠合柱的应力应变云图以及荷载-位移曲线。结果表明:试验结果与数值模拟结果基本吻合,验证了叠合柱有限元模型的合理性;加载结束,叠合柱中部呈鼓曲破坏,表现为再生混凝土保护层压碎脱落,钢筋和钢管局部鼓曲,核心再生混凝土压碎等;随着再生混凝土强度等级增加,叠合柱承载力和耗能均逐渐提高;设置拉结筋可显著提高叠合柱承载力和耗能能力,但延性仅有小幅度提高;增大箍筋间距和长细比,叠合柱承载力、延性和耗能均降低;随着方钢管壁厚增加,叠合柱承载力、变形性和耗能能力均显著增强。

H型钢连接L形方钢管混凝土组合异形柱偏压性能研究

为提升方钢管混凝土组合异形柱加工制作的便捷性与精度、减小焊接对板件变形的影响,提出了新型H型钢连接L形方钢管混凝土组合异形柱(LCFST-H),并研究其偏压荷载下的力学性能。设计了两个试件进行偏压加载试验,建立计算模型开展有限元分析。在验证有限元模型准确性的基础上,分析了H型钢连接板尺寸、方钢管截面尺寸、柱高度等参数对组合异形柱偏压受力性能的影响。结果表明:构件破坏形式为整体弯曲失稳与局部屈曲破坏,达到极限承载力后,单肢柱之间仍能通过H型钢连接板很好地协同工作,具备一定承载能力,体现出较高的延性性能。方钢管截面尺寸和柱高度对其偏压性能影响较大。结合相关规范,给出了H型钢连接L形方钢管混凝土组合异形柱单向偏压承载力计算公式,公式计算结果与有限元结果吻合较好。

L形方钢管再生混凝土组合异形柱压弯扭力学性能有限元分析

目的研究不同粗骨料取代率下L形方钢管再生混凝土组合异形柱在压弯扭等复合受力下的力学性能。方法采用ABAQUS软件建立L形方钢管再生混凝土组合异形柱有限元模型,分析其在压弯扭等复合受力下的受力机理,及常见参数对其力学性能的影响。结果在压弯扭复合受力作用下,不同粗骨料取代率下各试件的受力全过程均分为弹性阶段、弹塑性阶段和塑性阶段,当试件承受的轴压力大于0.4 F p且弯矩值大于0.6 M p时,试件抗扭承载力降低、延性较差。在相同的轴压力及弯矩作用下,随着粗骨料取代率的增大,试件的峰值扭矩和延性逐渐降低。结论在工程设计中,大轴压比试件应重点考虑扭矩对L形方钢管再生混凝土组合异形柱的影响。