【作者】 朱昌宏；

【导师】 蔡健；

【作者基本信息】 华南理工大学 ， 结构工程， 2010， 博士

【摘要】 带约束拉杆异形钢管混凝土柱是一种新型的结构构件。在钢管对核心混凝土约束相对弱处设置了约束拉杆,方形、矩形钢管对核心混凝土的有效约束增加,使到钢管的径向应力集度变化趋于平缓,相应地钢管对核心混凝土的平均侧向约束力增大,使核心混凝土的抗压强度得以较大幅度地提高;拉杆的弹性约束作用相当于对钢管横向弹性支撑作用,从而发生在一般形式方形、矩形钢管混凝土柱钢管局部过早出现屈曲的现象得到抑制和延迟。带约束拉杆异形钢管混凝土柱已经很好地应用于实际工程,但目前对其承载力和延性的研究尚不充分。本文作为带约束拉杆异形钢管混凝土柱力学性能系列研究的一部分,从带约束拉杆方形和矩形钢管混凝土短柱受力全过程的非线性分析程序编制、承载力计算以及延性计算三个方面深入地研究这种新型结构构件的轴压、单向偏压和双向偏压性能,为后续更为系统的研究奠定良好的基础。本文的主要工作和结论如下。(1)基于带约束拉杆方形、矩形钢管混凝土短柱内核心混凝土等效单轴受压本构关系,编制出可合理模拟带约束拉杆方形、矩形钢管混凝土短柱在轴压、单向偏压、双向偏压下受力全过程截面非线性分析计算程序,程序的计算结果和试验结果的比较表明,两者吻合良好(2)通过对不同参数的轴压承载力数值计算结果的回归分析,分别提出了适合带约束拉杆方形、矩形钢管混凝土构件轴压承载力计算的简化公式。(3)通过大量的参数分析,探究了轴压比、钢管壁厚、钢管强度、混凝土强度、约束拉杆间距、约束拉杆直径、截面尺寸等各种参数对带约束拉杆方形、矩形钢管混凝土短柱截面单向偏压承载力的影响规律。轴压比较低时,单向偏压承载力随轴压比的增大而增加;轴压比较高时,单向偏压承载力随轴压比的增大而减少。随着钢管强度的提高、钢管壁厚的增大、混凝土强度的提高、约束拉杆间距的减少、约束拉杆直径的增大,带约束拉杆方形、矩形钢管混凝土短柱单向偏压承载力也随之增大;混凝土强度的提高和约束拉杆直径的增大的影响效果不如其他因素明显。通过对数值计算结果的回归分析,分别提出了适合带约束拉杆方形、矩形钢管混凝土构件单向偏压承载力计算的简化公式。(4)荷载角对带约束拉杆方形、矩形钢管混凝土短柱承载力有较大影响;对于方形截面短柱,在荷载角α= 0(或90°),截面的抗弯承载力最高;在荷载角α= 45°处,截面的抗弯承载力最低;从荷载角为0逆时针到45°,承载力也随之从最大值减小至最小值。对于矩形截面短柱,在荷载角α= 0,截面的抗弯承载力最高;在荷载角α=60°处,截面的抗弯承载力最低;从荷载角为0逆时针到60°,承载力也随之从最大值减小至最小值,而后截面承载力又逐渐增加,直至90°处,达到另一个大值。不同荷载角α下各参数对带约束拉杆方形、矩形钢管混凝土短柱的n- M曲线和M ?φ曲线的影响规律基本相同,不同参数下的M_x / M_x’ -M_y /M_y’相关曲线均为以x、y轴为对称轴的封闭曲线,通过对数值计算结果的回归分析,分别提出了适合带约束拉杆方形、矩形钢管混凝土构件双向偏压承载力计算的简化公式。(5)通过大量的参数分析,探究了轴压比、钢管壁厚、钢管强度、混凝土强度、约束拉杆间距、约束拉杆直径、截面尺寸等各种参数对带约束拉杆方形、矩形钢管混凝土短柱截面单向偏压曲率延性系数的影响规律。随着轴压比的降低、钢管强度的提高、钢管壁厚的增大、约束拉杆间距的减少、约束拉杆直径的增大,带约束拉杆方形、矩形钢管混凝土短柱单向偏压曲率延性系数也随之增大;约束拉杆直径的增大的影响效果不如其他因素明显;混凝土强度的提高反而降低曲率延性系数。通过对数值计算结果的回归分析,分别提出了适合带约束拉杆方形、矩形钢管混凝土构件单向偏压曲率延性系数计算的简化公式。(6)荷载角对带约束拉杆方形、矩形钢管混凝土短柱截面的曲率延性系数影响非常显著;在荷载角α= 0°(或90°),截面的曲率延性系数最小;在荷载角α= 45°附近处,截面的曲率延性系数最大;从荷载角为0°逆时针到45°,曲率延性系数也随之从最小值增加至最大值。通过对数值计算结果的回归分析,分别提出了适合带约束拉杆方形、矩形钢管混凝土构件双向偏压曲率延性系数计算的简化公式。更多还原

【Abstract】 Special-shaped (including square, rectangle, L-shaped and T-shaped, et al.) concrete-filled steel tubular (CFT) column with binding bars is a new type structural member for buildings. For the square or rectangle concrete-filled steel tube columns with binding bars (SCFT-WB or RCFT-WB), by setting binding bars at the middle of each cross-sectional side, the distribution of lateral confining stress from the steel tube to the core concrete becomes more uniform, and the corresponding average lateral confining stress to the core concrete becomes larger, as a result, the confinement effect of the steel tube on the core concrete is enhanced, significant enhancement of the compressive strength of core concrete can be found. The behavior of the outward local buckling of the steel plates of the square or rectangle CFT columns is delayed or even avoided before the ultimate strength is reached, because the binding bars act as lateral constraining and constrain the lateral deformation of the tubes.Special-shaped concrete-filled steel tubular (CFT) columns with binding bars have been widely used in practical engineering projects, but researches on the bearing capacity and ductility are not sufficient. As a part of the study on the mechanical behaviors of special-shaped concrete-filled steel tubular (CFT) columns with binding bars, an extensively study on the behaviors of bearing capacity and ductility of the SCFT-WB or RCFT-WB stub columns subjected to axial load, uniaxial compressive load, and biaxial compressive load are conducted, based on the fiber element analysis program with nonlinear constitutional relationship of the core concrete, including the following main aspects.(1) The fiber element analysis technique is used to conduct the load-strain relationship curves of the SCFT-WB and RCFT-WB stub columns subjected to axial compressive load, uniaxial compressive load, and biaxial compressive load, based on the equivalent uniaxial constitutional relationship for the encased concrete of square or rectangle steel tubular with binding bars. The load-strain relationship curves predicted by the program agree well with the experimental ones.(2) The fiber element analysis program developed is used to investigate the effects of varied parameters on the bearing capacity of SCFT-WB or RCFT-WB stub columns subjected to axial load, and simplified formulas to predict the bearing capacities are suggested.(3) The fiber element analysis program developed is used to investigate the effects of ratios of axial compression stress to strength, sectional steel ratios, steel yield strengths, concrete cube strengths, the restraint coefficients of binding bars including spacings and diameters of the binding bars, and sectional aspect ratios on the bearing capacity of SCFT-WB or RCFT-WB stub columns subjected to uniaxial compressive load. The flexural strength increases by increasing the ratio of axial compression stress to strength when it is relatively small, while that decreases by increasing the ratio of axial compression stress to strength when it is relatively large. Furthermore, the flexural strength increases by increasing the sectional steel ratios, steel yield strengths, concrete cube strengths, and restraint coefficients of binding bars, in which the effects of concrete cube strengths and diameters of the binding bars on the flexural strength are inferior to the others. Based on the parameter analysis results, simplified formulas to predict the bearing capacities of SCFT-WB and RCFT-WB stub columns subjected to uniaxial compressive load are suggested, respectively.(4) Significant effects of load angles on the bearing capacity of SCFT-WB and RCFT-WB stub columns subjected to biaxial compressive load can be found. For the SCFT-WB stub columns, the maximum and minimum flexural strength are obtained at load angle 0°(or 90°) and 45°, respectively, and it decreases from the load angle 0°to 45°. For the RCFT-WB stub columns, the maximum and minimum flexural strength are obtained at load angle 0°and 60°, respectively, and it decreases from the load angle 0°to 60°, and increases again from 60°to 90°. Similar effects of varied parameters at different load angles on the N-M and M-φinteraction diagrams of the SCFT-WB and RCFT-WB stub columns can be found, and the M_x/M_x’-M_y/M_y’interaction diagrams are closed curves, symmetric to the x and y axis. According to the features of M_x/M_x’-M_y/M_y’interaction diagrams, simplified formulas to predict the bearing capacities of SCFT-WB and RCFT-WB stub columns subjected to biaxial compressive load are suggested, respectively.(5) The fiber element analysis program developed is used to investigate the effects of ratios of axial compression stress to strength, sectional steel ratios, steel yield strengths, concrete cube strengths, the restraint coefficients of binding bars including spacings and diameters of the binding bars, and sectional aspect ratios on the coefficient of curvature ductility of SCFT-WB or RCFT-WB stub columns subjected to uniaxial compressive load. The coefficient of curvature ductility increases by decreasing the ratio of axial compression stress to strength and the concrete cube strength, increasing the sectional steel ratios, steel yield strengths, and restraint coefficients of binding bars, in which the effect of diameters of the binding bars on the coefficient of curvature ductility is inferior to the others. Based on the parameter analysis results, simplified formulas to predict the coefficients of curvature ductility of SCFT-WB and RCFT-WB stub columns subjected to uniaxial compressive load are suggested, respectively. (6) Significant effects of load angles on the coefficient of curvature ductility of SCFT-WB and RCFT-WB stub columns subjected to biaxial compressive load can be found. The maximum and minimum coefficient of curvature ductility are obtained at load angle 45°and 0°(or 90°), respectively, and it increases from the load angle 0°to 45°. Based on the parameter analysis results, simplified formulas to predict the coefficients of curvature ductility of SCFT-WB and RCFT-WB stub columns subjected to biaxial compressive load are suggested, respectively.更多还原