Finite element analysis on axial loading behavior of stub columns of square concrete-filled steel tube with diagonal ribs

为改善方钢管对核心混凝土的约束效应和薄壁钢管混凝土柱的受力性能,提出了带斜拉肋方钢管混凝土柱,其中斜拉肋通长并焊接于钢管两邻边的三分点处。基于有限元软件ABAQUS,对带斜拉肋的方钢管混凝土短柱的轴压受力性能进行了精细化模拟,分析了斜拉肋的设置与否、钢管宽厚比、混凝土强度、斜拉肋厚度、钢材强度、斜拉肋与钢管之间焊缝间隔长度及斜拉肋孔径、间距对轴压力学性能的影响。结果表明：设置斜拉肋可使方钢管混凝土短柱的轴压承载力平均提高14.9%左右,并使方钢管对核心混凝土的约束效果增加,即组合作用系数从1.031平均增加到1.103,尤其可以明显改善大宽厚比方钢管混凝土柱的轴压承载力及组合作用;采用较薄厚度的斜拉肋,可使短柱的组合作用更好,并能充分发挥材料的性能。     

带斜拉肋方钢管混凝土短柱轴压性能有限元分析

为改善方钢管对核心混凝土的约束效应和薄壁钢管混凝土柱的受力性能,提出了带斜拉肋方钢管混凝土柱,其中斜拉肋通长并焊接于钢管两邻边的三分点处。基于有限元软件ABAQUS,对带斜拉肋的方钢管混凝土短柱的轴压受力性能进行了精细化模拟,分析了斜拉肋的设置与否、钢管宽厚比、混凝土强度、斜拉肋厚度、钢材强度、斜拉肋与钢管之间焊缝间隔长度及斜拉肋孔径、间距对轴压力学性能的影响。结果表明:设置斜拉肋可使方钢管混凝土短柱的轴压承载力平均提高14.9%左右,并使方钢管对核心混凝土的约束效果增加,即组合作用系数从1.031平均增加到1.103,尤其可以明显改善大宽厚比方钢管混凝土柱的轴压承载力及组合作用;采用较薄厚度的斜拉肋,可使短柱的组合作用更好,并能充分发挥材料的性能。     

薄壁方钢管混凝土短柱承载性能非线性有限元分析

采用ANSYS软件,对薄壁方钢管混凝土短柱的承栽性能进行非线性有限元分析.考虑轴压作用下带肋与不带肋两种截面形式的薄壁方钢管混凝土短柱力学性能,并得出其破坏模态,计算结果与试验结果吻合较好.针对该类构件,探讨加劲肋和钢管强度对其承载力的影响.结果表明,设置加劲肋能有效提高薄壁方钢管混凝土短柱的轴压承载力,与不带肋短拄相...     

带肋方钢管混凝土轴压短柱试验研究及有限元分析

以方钢管宽厚比和加劲肋高厚比为主要变化参数,进行了14个带肋方钢管混凝土轴压短柱试验研究;同时采用有限元软件ABAQUS对带肋方钢管混凝土轴压短柱的荷载-变形关系进行了计算,计算结果与试验结果吻合良好。同时从应力-应变关系、核心混凝土和钢管的纵向应力分布及其相互作用等方面对比分析了无肋、单肋和双肋方钢管混凝土轴压短柱的受力性能。分析结果表明：设置加劲肋不仅提高了核心混凝土的纵向应力,而且明显减小了钢管管壁的拉应力区范围,改善了管壁的稳定性;带肋试件的约束作用主要集中在钢管角部和加劲肋处,随着每边加劲肋数量的增加,角部约束力明显增大。图13表1参11     

方钢管约束型钢混凝土短柱抗震性能试验研究

进行了3个剪跨比为1.5的方钢管约束型钢混凝土短柱和1个相同用钢量的型钢混凝土对比试件的拟静力试验研究,试件的主要变化参数为轴压比(0.3,0.4和0.5)。试验结果表明：轴压比为0.3的方钢管约束型钢混凝土柱的破坏模式为弯曲破坏,而轴压比为0.4和0.5的方钢管约束型钢混凝土柱的破坏模式为剪切破坏和粘结破坏相结合。相同用钢量条件下,方钢管约束型钢混凝土短柱的受剪承载力、延性、层间变形能力和耗能性能明显优于型钢混凝土柱。随轴压比的增加,方钢管约束型钢混凝土短柱的受剪承载力提高,但延性和极限变形能力降低。对钢管的弹塑性应力分析结果表明：水平荷载施加过程中,发生弯曲破坏试件的钢管不屈服,而发生剪切破坏试件的钢管在下降段屈服。图8表2参13     

带肋薄壁方钢管混凝土轴压短柱受力性能试验研究

为研究带肋薄壁方钢管混凝土轴压短柱的受力性能,以钢管宽厚比、加劲肋宽度和加劲肋个数为参数,对26个薄壁方钢管混凝土短柱进行了试验研究。研究结果表明:对于无肋试件,在达到承载力以前管壁已经发生鼓曲,且试件宽厚比越大,鼓曲越早发生,鼓曲部位的钢管截面越早退出工作,没有发挥出钢管混凝土的优势。设置加劲肋后薄壁方钢管混凝土短柱的受力性能得到明显改善,钢管壁的局部鼓曲得以延缓,材料强度得到了充分利用,试件承载力提高。当试件宽厚比为60、80时,加劲肋宽度对试件承载力影响最明显,加劲肋宽度越大,承载力越高,增加加劲肋个数对试件承载力影响不大;而当试件宽厚比为100时,设置单个加劲肋已不能满足对管壁局部屈曲的抗弯刚度要求,必须增加加劲肋的个数以增加约束钢管变形的支撑点,减小管壁局部屈曲的波长,提高试件局部屈曲的临界荷载。同时利用ABAQUS有限元计算软件对薄壁带肋方钢管混凝土轴压短柱的受力全过程进行了模拟,并将试验结果与有限元模拟结果进行了对比,两者吻合良好,为下一步分析奠定基础。     

Experimental research on mechanical behavior of concrete-filled thin-walled stiffened square steel tubular short column under axial load

为研究带肋薄壁方钢管混凝土轴压短柱的受力性能,以钢管宽厚比、加劲肋宽度和加劲肋个数为参数,对26个薄壁方钢管混凝土短柱进行了试验研究。研究结果表明：对于无肋试件,在达到承载力以前管壁已经发生鼓曲,且试件宽厚比越大,鼓曲越早发生,鼓曲部位的钢管截面越早退出工作,没有发挥出钢管混凝土的优势。设置加劲肋后薄壁方钢管混凝土短柱的受力性能得到明显改善,钢管壁的局部鼓曲得以延缓,材料强度得到了充分利用,试件承载力提高。当试件宽厚比为60、80时,加劲肋宽度对试件承载力影响最明显,加劲肋宽度越大,承载力越高,增加加劲肋个数对试件承载力影响不大;而当试件宽厚比为100时,设置单个加劲肋已不能满足对管壁局部屈曲的抗弯刚度要求,必须增加加劲肋的个数以增加约束钢管变形的支撑点,减小管壁局部屈曲的波长,提高试件局部屈曲的临界荷载。同时利用ABAQUS有限元计算软件对薄壁带肋方钢管混凝土轴压短柱的受力全过程进行了模拟,并将试验结果与有限元模拟结果进行了对比,两者吻合良好,为下一步分析奠定基础。     

PBL加劲型方钢管混凝土短柱轴压承载力统一解

对于特定的PBL加劲型方钢管混凝土轴压短柱,考虑混凝土榫形成的剪力键提供的有效作用,对PBL加劲肋进行受力分析.引入混凝土有效约束系数,采用统一强度理论,考虑中间主应力和材料拉压比的影响,推导了PBL加劲型方钢管混凝土短柱轴压极限承载力的计算公式,并对其影响因素进行了分析.将计算结果与文献试验结果进行对比,吻合较好,验证了所给公式的正确性.研究结果表明,PBL加劲型方钢管混凝土短柱的轴压承载力随双剪统一强度理论参数b、混凝土内摩擦角、加劲肋的宽度和厚度的增大而提高.所得结果可以为PBL加劲型方钢管混凝土短柱轴压承载力的研究提供参考.     

穿孔肋拉杆约束方钢管混凝土短柱轴压试验研究

为研究穿孔肋拉杆约束方钢管混凝土短柱的轴压性能,完成了穿孔肋拉杆约束方钢管混凝土短柱与仅设约束拉杆、仅设加劲肋、普通方钢管混凝土短柱对比试件的轴心受压试验;观察了试件的受力全过程和破环特征,分析了试件的荷载-位移曲线、荷载-应变曲线、轴压承载力、延性、含钢率等性能指标.结果 表明:穿孔肋拉杆的设置使钢管壁对核心混凝土的约束作用更趋均匀,改变了钢管的局部屈曲变形状态,显著提高了方钢管混凝土柱的轴压承载力和延性;当柱截面含钢率相同时,与仅设加劲肋的钢管混凝土柱相比,穿孔肋拉杆约束方钢管混凝土短柱的轴压承载力提高了7％,延性提高了30％;与仅设约束拉杆的方钢管混凝土柱相比,穿孔肋拉杆约束方钢管混凝土柱的轴压极限承载力提高了10％,延性提高了19％.     

轴压作用下矩形钢管混凝土柱性能研究

为对比分析设置不同传力构件对矩形钢管混凝土柱在轴压作用下共同工作性能的影响,在钢管壁内侧设环向加劲肋和栓钉,不考虑钢管壁与核心混凝土间的摩擦粘结作用,利用有限元软件ABAQUS,进行轴压作用下矩形钢管混凝土柱共同工作性能研究分析。结果表明,在矩形钢管混凝土柱楼层节点区钢管壁内设环向加劲肋和栓钉,混凝土浇筑理想施工情况下,可以将作用在钢管壁上的部分外荷载传递于核心混凝土,迫使混凝土参与部分工作,改善了矩形钢管混凝土柱的受力性能,且栓钉作用较小。     

Seismic behavior and strength of tubed steel reinforced concrete (SRC) short columns

The seismic behavior of tubed SRC short columns has been investigated by testing eight specimens subjected to combined constant axial compression and lateral cyclic load. Three circular tubed SRC columns (CTSRC) and three square tubed SRC (STSRC) columns were tested in this research with two common SRC columns for comparison. Different axial load ratios (n₀=0.3, 0.4 and 0.5) have been adopted for the constant axial load. The test results indicate that the shear strength, plastic deformation capacity, ductility index, and energy dissipating capacity of the tubed SRC short columns were much higher than those of the SRC columns with the same steel ratio and axial compressive load. The lateral load strength of CTSRC and STSRC short columns increased with an increment in axial load level, while the axial load ratio has no obvious effect on the plastic deformation capacity of CTSRC and STSRC short columns. The steel tubes prevented the shear failure of the concrete more effectively in the circular columns than in the square ones. Shear connector studs should be used in CTSRC and STSRC short columns to prevent bond failure between concrete and flanges of the steel section. A modified ACI design method was adopted to calculate the nominal shear strength of STSRC columns as well as CTSRC columns.     

Hysteretic behavior and design of square tubed reinforced and steel reinforced concrete (STRC and/or STSRC) short columns

The square tubed reinforced and steel reinforced concrete (STRC and STSRC) short columns are ordinary RC and/or SRC short columns where most of the lateral reinforcement is in the form of thin-walled steel tubes. In this study, six specimens of STRC and STSRC short columns were experimentally tested under constant axial compression and cyclic lateral load to investigate the seismic performance of both kinds of structure. The main parameters were the axial load ratio and status of longitudinal reinforcement. Nonlinear 3D finite element model was developed to simulate the monotonic behavior and strength of tested specimens. The behavior and strength of extra assumed specimens were predicted using the developed FEM model. Depending on the test and analysis results, a design formula was proposed to predict the shear strength of STRC and/or STSRC short columns.     

Shear strength and behavior of tubed reinforced and steel reinforced concrete (TRC and TSRC) short columns

Tubed RC and SRC short columns are special kinds of concrete filled tubular columns but the steel tube does not pass through the beam–column connection and is shorter than concrete core. In areas that suffered earthquakes, the short columns are vulnerable to brittle shear failure. TRC and TSRC short columns are widely used in bridges, high-rise buildings and large factories. So it is important to investigate the behaviors and approaches to improve the ductility of these kind of columns. The aim of this study is to develop a nonlinear finite element model (FEM) for TRC and TSRC short columns and to compare the results with those experimentally captured. Depending on the FEM results, the elastic–plastic method was used to analyze the stress status of the steel tube. A modified ACI design method is adopted to calculate the nominal shear strength of TRC and TSRC short columns based on the FEM and analysis results.     

Seismic behavior and shear strength of tubed RC short columns

Reinforced concrete (RC) short columns are vulnerable to brittle shear failure during an earthquake. The objective of this research is to evaluate the performance enhancement of RC short columns tubed with circular or square tubes. Eight short columns were tested under combined constant axial load and cyclic lateral load. The tested specimens included three circular tubed RC (CTRC) columns and three square tubed RC (STRC) columns. Two common RC short columns including one circular RC column and one square RC column were also tested as control specimens. The test results indicated that common RC short columns suffered brittle shear failure with little ductility, while the ductility of tubed RC short columns was excellent due to the effective confinement of the outer thin tube to the core concrete. The lateral load strength of CTRC short columns increases with the increasing of axial load ratio, while the axial load ratio has little effect on the plastic deformation capacity of CTRC short columns. The shear strength increases with increasing of axial load ratio, while the plastic deformation capacity decreases with increasing of axial load ratio for STRC short columns. A circular tube prevents the core concrete from shear failure more effectively than a square tube for the tubed RC short columns. A modified ACI design method is adopted to calculate the nominal shear strength of STRC columns as well as CTRC columns based on the test and analysis results.     

方钢管约束钢筋高强混凝土超短柱抗震性能试验研究

本文进行3个剪跨比为1.5的方钢管约束钢筋高强混凝土超短柱和1个钢筋混凝土对比试件的试验研究,试验中的主要参数为轴压比(0.35,0.45和0.55)。试验结果表明,由于钢管对核心高强混凝土的约束作用和钢管的抗剪作用,方钢管约束钢筋混凝土超短柱的抗剪承载力、延性、变形能力和耗能性能明显高于钢筋混凝土超短柱。轴压为0.35的方钢管约束钢筋混凝土超短柱的破坏模式为弯曲破坏,而轴压比为0.45和0.55的方钢管约束钢筋混凝土超短柱的破坏模式为剪切破坏。随轴压比的提高,方钢管约束钢筋混凝土超短柱的抗剪承载力提高,但延性系数和极限变形能力降低。对钢管的弹塑性应力分析结果表明,水平荷载施加过程中,发生弯曲破坏试件的钢管不屈服,而发生剪切破坏试件的钢管可能在下降段屈服。根据试验结果和钢管应力分析结果建立方钢管约束钢筋混凝土柱的抗剪承载力公式,提出设计建议,可为工程实践提供参考。     

Nonlinear behavior of concrete-filled stainless steel stiffened slender tube columns

This paper investigates the nonlinear behavior of concrete-filled high strength stainless steel stiffened slender square and rectangular hollow section columns. The stiffened slender tubes had overall depth-to-plate thickness (D/t) ratios ranging 60–160. The concrete strengths covered normal and high-strength concrete. The investigation focused on short axially loaded columns. A nonlinear finite element (FE) model has been developed to study the behavior of the concrete-filled stiffened tube columns. A parametric study was conducted to investigate the effects of cross-section geometry and concrete strength on the behavior and strength of the columns. The results of the concrete-filled stiffened tube columns were compared with the results of the companion concrete-filled unstiffened tube columns. It is shown that the concrete-filled stiffened slender tube columns offer a considerable increase in the column strength and ductility than the concrete-filled unstiffened slender tube columns. The column strengths obtained from the FE analysis were compared with the design strengths calculated using the American specifications and Australian/New Zealand standards. A design equation was proposed for concrete-filled stainless steel stiffened slender tube columns. It is shown that the proposed modified equation provides more accurate design strengths compared to the American and Australian/New Zealand predictions.     

Behavior of square tubed reinforced-concrete short columns subjected to eccentric compression

This paper presents the experimental and theoretical studies on square tubed reinforced-concrete (TRC) short columns under eccentric compression. The main parameters of the test specimens included eccentricity and width-to-thickness ratio of the steel tube. The axial load versus lateral deformation curves, stresses in the steel tubes and the observed failure modes were discussed. The test results indicated that the eccentrically loaded specimens exhibited good ductile behavior with a bending failure mode. A new approach to determine the effective lateral confining pressure for TRC columns with square section was proposed. A numerical analysis model was developed to simulate the mechanical behaviors of square TRC short columns. Valuable attempts were made to describe the variation rules between the parameters in stress block method for tubed concrete and the magnitude of confinement. Furthermore, the axial force versus moment capacity interaction diagrams of square TRC columns were calculated.     

圆钢管约束钢筋混凝土短柱抗震性能试验研究

进行了3个剪跨比为1.5的圆钢管约束钢筋混凝土短柱和1个钢筋混凝土对比试件的拟静力试验研究,试验中的主要参数为轴压比(0.35,0.45和0.55)。试验结果表明：钢筋混凝土短柱的破坏模式为剪切破坏,延性和变形能力很差;圆钢管约束钢筋混凝土短柱的破坏模式为弯曲破坏,延性和变形能力优越。外包钢管对核心混凝土的约束作用限制了核心混凝土的受剪开裂,改变了钢筋混凝土短柱的破坏模式,显著提高了钢筋混凝土短柱的受剪承载力、延性、变形能力和耗能性能。随轴压比的提高,圆钢管约束钢筋混凝土短柱的水平承载力提高,延性系数降低,但轴压比对圆钢管约束钢筋混凝土短柱的极限变形能力无明显影响。对钢管的弹塑性应力分析结果表明：水平荷载施加过程中,钢管并未受剪屈服。根据试验结果建立了圆钢管约束钢筋混凝土短柱的荷载-位移恢复力模型,提出了设计建议,可为工程实践提供参考。图10表2参12     

钢管混凝土短柱（剪力键）受剪性能试验研究

通过对方钢管和圆钢管混凝土短柱（剪力键）进行受剪性能试验研究,分析钢管混凝土短柱（剪力键）在单调加载和反复加载条件下的受剪性能,得到方形和圆形截面钢管混凝土短柱（剪力键）无轴力剪切的荷载 位移曲线、荷载-位移滞回曲线及骨架曲线等。用精细有限元方法,对试验进行了数值模拟,通过合理的材料本构关系、破坏模式,所得有限元计算值与试验结果吻合较好,极限荷载的相对误差在8.84%之内。研究表明：钢管混凝土短柱（剪力键）具有较好的受剪性能,单调荷载作用下,方形截面和圆形截面短柱（剪力键）的相对变形均超过4.0%;循环荷载作用下,圆钢管混凝土短柱（剪力键）的滞回环更饱满、延性系数及耗能能力均优于方钢管混凝土短柱（剪力键）;理论分析方法可靠。