Experimental investigation of axially loaded steel fiber reinforced high strength concrete-filled steel tube columns

An experimental study on the compressive behavior of steel fiber reinforced concrete-filled steel tube columns is presented. Specimens were tested to investigate the effects of the concrete strength, the thickness of steel tube and the steel fiber volume fraction on the ultimate strength and the ductility. The experimental results indicate that the addition of steel fibers in concrete can significantly improve the ductility and the energy dissipation capacity of the concrete-filled steel tube columns and delay the local buckling of the steel tube, but has no obvious effect on the failure mode. It has also been found that the addition of steel fibers is a more effective method than using thicker steel tube in enhancing the ductility, and more advantageous in the case of higher strength concrete. An analytical model to estimate the load capacity is proposed for steel tube columns filled with both plain concrete and steel fiber reinforced concrete. The predicted results are in good agreement with the experimental ones obtained in this work and literatures.

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 of Composite Columns Filled with Eucalyptus nitens Timber under Axial Compression

Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an innovative composite column.The composite column was comprised of a rectangular steel tube with E.nitens timber infill.The nonlinear compressive behaviour of the composite column filled with E.nitens wood for both dry and wet conditions was examined.The same tests on rectangular steel tubes and bare dry and wet E.nitens samples were also undertaken as a comparison.For samples with different conditions,the ultimate capacity was evaluated and the effect of each condition on the compressive behaviour of the composite column was clarified.The steel tubes showed greater ductile behaviour,and more ductility was found in the wet samples.The steel tubes with E.nitens timber infill samples exhibited a greater linear elastic range connected with higher maximum loads,while the bare timber samples could support only lower maximum loads.The results from this research were promising for the use of rectangular steel tubes with E.nitens timber infill in structural applications.

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.

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.

内置工字型CFRP型材高强圆钢管高强混凝土轴压短柱组合效应分析

目的 研究内置工字型CFRP型材的高强圆钢管高强混凝土短柱在轴心压力作用下三种材料的组合效应。方法 采用有限元分析软件ABAQUS对其进行数值模拟,通过相关试验验证模型的准确性,并对典型构件的破坏形态、受力全过程曲线进行分析,揭示构件各组成部分之间的相互作用和工作机理,评估CFRP配置率、钢材屈服强度、混凝土抗压强度、约束效应系数对组合效应的影响。结果 在高强圆钢管高强混凝土柱中内置CFRP型材,对构件的延性及安全裕度有显著提高,并改善了高强圆钢管对高强混凝土的约束,提高了构件的组合效应。结论 CFRP配置率控制在5.9%~8.4%,约束效应系数在1.2~1.4,钢材屈服强度不大于770 MPa时,构件中三种材料组合效应最佳。

高温后钢管高强混凝土柱的黏结性能

为了研究高温后钢管高强混凝土柱的黏结性能,通过有限元软件ABAQUS建立模型,并与已有试验结果进行验证,吻合良好。研究表明:钢管高强混凝土柱的黏结应力随着温度的升高呈现出先增加后减小的趋势;黏结应力随着混凝土强度的增大而增大,随着径厚比的增大而减小;长径比在2.74~7.72的范围内,随着长径比的增加,黏结力逐渐增加;黏结界面破坏的速度随温度的增加而减缓;随着温度的增加耗能因子呈现先增大后减小的趋势。

钢管混凝土叠合柱-H型钢梁外套筒式连接节点抗震性能试验与有限元研究

以钢管混凝土叠合柱为研究对象,设计了一种高强对穿螺栓连接的外套筒式梁柱节点。为了研究该新型节点的抗震性能和破坏机理,对3个缩尺比为1∶2的节点进行了拟静力试验。观察节点损伤过程及破坏模式,分析了梁端荷载-位移滞回曲线、骨架曲线、节点延性及耗能能力,采用ABAQUS软件建立有限元模型,研究套筒宽厚比和加强肋板厚度对节点抗震性能影响。试验及有限元研究结果表明:节点滞回曲线饱满,延性系数介于3.13~4.19之间,等效黏滞阻尼系数介于0.211~0.296之间,节点域的变形较大且耗能能力较强;随着套筒厚度增大,核心区混凝土开裂减少,破坏位置由节点外移至梁端截面;减小套筒宽厚比和增大加强肋板厚度可以有效提高节点刚度。为保证外套筒式节点达到刚性节点要求,建议套筒宽厚比不大于25,加强肋板厚度不小于梁翼缘厚度。

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。

十字形钢管束高强混凝土组合剪力墙的抗剪承载力研究

为研究不同参数对十字形钢管束高强混凝土组合剪力墙抗剪承载力的影响,通过ABAQUS有限元软件建立了十字形钢管束高强混凝土组合剪力墙的有限元模型,重点考察钢材强度、混凝土强度、钢板厚度、钢管厚度、轴压比、墙体长度、墙体高度、腔体长度等参数对此类组合剪力墙抗剪承载力的影响。分析结果表明:随着钢材强度、钢板厚度、钢管厚度、墙体长度的增加和墙体高度的减小,试件的抗剪承载力呈显著增大趋势;随着混凝土强度的提高和腔体长度的减小,试件的抗剪承载力略呈增大趋势;当轴压比较小时(n∈(0,0.3]),轴压比对试件的抗剪承载力有一定的提高作用;当轴压比较大时(n∈(0.3,0.8]),随着轴压比的增加其抗剪承载力逐渐降低。最后,提出了十字形钢管束高强混凝土组合剪力墙的抗剪承载力计算公式。

偏心率对工字型CFRP-高强圆钢管高强混凝土短柱力学性能的影响

目的研究偏心率对内置工字型CFRP型材的高强圆钢管高强混凝土短柱力学性能的影响。方法利用ABAQUS有限元软件建立了工字型CFRP-高强圆钢管高强混凝土短柱模型,分析不同偏心率下构件的受力-变形关系、各材料分担荷载以及应力发展,探究混凝土强度、钢材屈服强度、含钢率和CFRP型材对组合柱力学性能的影响。结果随着偏心率的增大,构件延性提高,初始刚度与极限承载力降低,且降低幅度减小,偏心率与极限承载力呈非线性关系;偏心率越小,加入CFRP型材对组合柱承载力的提高越显著。结论偏心率越大,混凝土强度的利用率越低,钢管力学性能发挥越充分。偏心率小于0.328时,建议采用增大混凝土强度的方式增加构件极限承载力;偏心率大于0.328时,建议采取增大钢材屈服强度和含钢率的方式增加构件的极限承载力。

内置方钢管高强再生混凝土叠合柱轴压性能有限元分析

为研究内置方钢管高强再生混凝土柱的轴压性能,使用ABAQUS软件对现有试验的2个试件进行建模分析,验证了模型的准确性,并在可靠的模型基础上进行了13个试件的参数分析,变化参数为方钢管厚度、方钢管强度和长细比。结果表明:所建立的有限元模型出现了与试验结果一致的纵筋屈曲和钢管撕裂变形,荷载–轴向位移曲线高度一致,极限承载力平均误差在5%以内;钢管厚度的提高对轴压承载力和刚度影响不大,钢管屈服强度的提高对轴压承载力和残余承载力提升较大;随着长细比的增大,叠合柱的轴压刚度和极限承载力出现明显退化,拟合了轴压稳定系数与长细比之间的数值计算方法,可供叠合柱设计参考。

型钢UHTCC短柱的抗震性能研究

将具有良好控裂耗能能力和抗剥落性能的水泥基材料UHTCC应用于型钢混凝土SRC短柱,制作并完成了7个型钢-UHTCC(SUHTCC)短柱和1个SRC对比短柱的拟静力试验。试验主要变量为:配箍率、轴压比和翼缘栓钉布置。结果表明:UHTCC的使用可有效避免SRC短柱粘结裂缝的滋生,减缓剪切主裂缝的扩展,能够将SRC短柱的脆性剪切粘结混合破坏模式转变为延性较好的剪切破坏模式,大幅提升短柱的震后完整性;对SUHTCC短柱,增大配箍率对承载力几乎没有影响,但需确保箍筋最大间距以延缓粘结破坏,高配箍率的试件能显示出较好的峰后滞回曲线,具有较高的极限变形和耗能;轴压比对抗震破坏形态和力学性能影响较小,高轴压比下依然拥有较高的大变形能力和良好的抗震耗能;与型钢翼缘没有布置栓钉的SUHTCC试件相比,布置栓钉的SUHTCC短柱表现出更为饱满的峰前抗震滞回曲线,对峰前行为的影响较为显著,但峰后破坏加快导致延性降低。最后采用3种不同规范对SUHTCC短柱受剪承载力进行了预测,初步验证了现行JGJ138-2016规范受剪承载力计算公式的适用性,并对SUHTCC短柱的剪切变形进行了定量分析,讨论了各参数对剪切变形的限制能力。

带加强筋的双钢管高强混凝土柱轴压性能研究

将普通螺纹钢置于内外钢管间的空隙制成带加强筋的双钢管高强混凝土柱,借助数值模拟研究该柱与普通双钢管混凝土柱在轴向荷载下的受力差异,以及加强筋平面角度、竖向间距和强度等级等参数对其轴向荷载下力学性能的影响。结果发现:带加强筋的双钢管混凝土柱前期力学性能略高于普通双钢管混凝土柱,后期延性显著高于普通双钢管混凝土柱;不同参数对其轴压性能的影响程度不同,加强筋平面角度显著,竖向间距次之,加强筋强度影响极小。

钢管高强混凝土叠合柱抗震性能与受力机理的试验研究

本文通过四个钢管高强混凝土叠合柱与一个普通高强混凝土柱在周期往复荷载作用下抗震性能的试验研究，比较了两种柱的抗震能力和破坏形式；然后根据试验结果，分析了叠合柱受水平荷载作用时，外围钢筋混凝土与核心钢管混凝土之间轴力及水平力的分配关系；

钢管高强混凝土叠合柱的抗震性能研究

通过周期性往复试验，研究了钢管高强混凝土叠合柱的破坏形态、耗能能力、延性、承载力以及各组成部分共同工作等内容，并与钢管高强混凝土核心柱进行了对比；随后通过计算，讨论了叠合柱中有关参数对其极限承载力的影响；最后给出了叠合柱正截面极限承载力的简化计算方法。

钢骨为圆钢管的高强混凝土柱斜截面承载力计算

介绍了以圆钢管为钢骨的劲性高强混凝土柱的剪切性能试验的试验概况,在此基础上研究了它的斜截面承载力计算方法。在计算时,采用了将构件分成几个独立的抗力机构,相互叠加构成构件抗力体系的计算方法的计算模型。进而利用剪切性能试验得到的数据结果进行参数回归,得到以圆钢管为钢骨的劲性高强混凝土柱的斜截面承载力计算公式。

钢骨-方钢管自密实高强混凝土轴压长柱试验研究

钢骨-方钢管自密实高强混凝土柱是一种重载柱设计的新模式．为了研究该组合柱的轴压稳定性能，以长细比（A）为主要参数，进行了8根组合长柱的轴心受压试验．试验结果表明：由于内填混凝土和钢骨的存在，组合柱试件具有良好的稳定性能；在研究的长细比范围内（λ=11～43），所有试件都具有较高的承载力和一定的延性，但是其承载能力和延性随长细比的增大明显降低．最后给出了钢骨-方钢管自密实高强混凝土柱的轴压承载力计算公式，公式计算值与试验值吻合良好．

内置CFRP圆管的方钢管高强混凝土轴压短柱承载力计算初探

目的研究内置CFRP圆管的方钢管高强混凝土轴压短柱的承载力.方法进行了12根内置CFRP圆管的方钢管高强混凝土轴压短柱和6根普通方钢管高强混凝土轴压短柱的试验研究和理论分析,探讨了与试件的含钢率及CFRP圆管与方钢管的相对配置率之间的关系以及它们对承载力的影响.结果承载力随着含钢率及CFRP圆管与方钢管的相对配置率的增大而提高,回归得到了内置CFRP圆管的方钢管高强混凝土轴压短柱的承载力计算初探公式.结论承载力计算公式的理论计算结果与试验结果吻合良好,证明了提出的计算公式的正确性.