【作者】 郑新志；

【导师】 蔡健；

【作者基本信息】 华南理工大学 ， 结构工程， 2014， 博士

【摘要】 矩形钢管混凝土的钢管对核心混凝土约束主要集中在角部，在四个侧边中部约束作用较小，所以矩形钢管对核心混凝土的整体约束效应远不及圆形钢管混凝土，导致其承载力远低于圆形钢管混凝土柱。与方形钢管混凝土相比，矩形钢管截面长宽边长不同，长边对核心混凝土的约束作用弱，较短边更易发生局部屈曲。但由于约束作用的存在，只要设置得当，其承载力比按钢管和混凝土两种材料单轴强度简单叠加计算要高。为了改善矩形截面钢管混凝土柱构件的力学性能，在矩形截面钢管混凝土柱中沿纵向每隔一定间距的横截面上设置横向水平约束拉杆（钢筋），一方面能限制该部位核心混凝土的横向变形，另一方面能为钢管提供侧向支撑作用而使钢板的局部屈曲强度提高。约束拉杆的设置能极大改进矩形钢管混凝土柱的力学性能，但约束拉杆之间区域仍出现弹塑性局部屈曲现象，对内填混凝土的约束作用受到削弱。劲化矩形钢管混凝土柱通过加设劲化带形成劲化带与约束拉杆的和谐搭配，在增加极少用钢量又不增加施工难度，影响施工进度的情况下，最大限度的减缓约束拉杆之间的弹塑性屈曲，提高侧面约束能力，改善矩形钢管混凝土柱的力学性能。本文对矩形钢管混凝土柱的劲化设计，基于已有研究成果，在满足高层建筑结构安全的前提下，能较大限度地用较薄的钢板厚度，实现较高的强度、刚度以及延性。基于上述分析，本文对劲化矩形钢管混凝土柱的轴压、偏压、滞回性能进行了系列研究。(1)以约束拉杆水平间距、纵向间距、劲化带截面、劲化带设置方式为研究参数，共进行10个方形钢管混凝土柱试件的轴压承载力试验。分析各参数对试件的破坏形态、受力特点、应变特点、承载力及延性等力学性能的影响，为后述的研究提供基本试验资料。(2)以钢板厚度、约束拉杆直径、约束拉杆强度、劲化带截面、劲化带设置方式为研究参数，采用拟静力试验方法对构件施加低周水平力反复荷载作用，共进行16个方形钢管混凝土柱试件的低周水平力反复荷载试验。分析在不同参数下，各个构件的滞回曲线、骨架曲线，从而计算出各个构件的承载力及其退化，刚度及其退化、位移延性系数、耗能能力。由试验结果采用三折线计算模型回归分析、确定了劲化方钢管混凝土柱的骨架曲线模型参数，为这种新型构件在超高层工程中设计分析提供参考。(3)对劲化矩形钢管混凝土柱的约束机理进行了分析。矩形钢管截面长边、短边对混凝土约束作用大小不同，及约束拉杆沿长边、短边布置数量不同。基于核心混凝土真三轴受压的特点，提出了劲化矩形钢板内核心混凝土的等效单轴本构关系。采用该本构关系对劲化矩形钢管混凝土轴压构件的荷载-变形关系曲线进行全过程数值分析，验证了计算曲线与试验曲线的吻合性。(4)为与试验监测结果相互印证，根据本文提出的劲化矩形钢板内填混凝土的本构关系，对所有试件进行了三维双重非线性有限元分析，深入揭示劲化带及约束拉杆对核心混凝土及钢管应力分布的影响，对各个试件进行了对比。有限元分析结果与试验结果基本相符。通过建立模型，扩大参数，利用有限元分析各种劲化方式、劲化参数下构件的侧向约束效果。(5)该类构件在各种劲化方式下的轴压承载力有很大差别，不能用一个统一的公式表述。采用本文提出的劲化矩形钢板混凝土本构关系，推导得出该类构件在各种劲化方式下的轴压承载力计算公式。采用本文提出的劲化矩形钢管混凝土柱的轴压承载力计算公式对轴压试件的承载力进行计算，计算结果与试验结果、有限元分析结果吻合良好；基于已有研究成果，本文方法能合理地评估劲化矩形钢管混凝土短柱的轴压承载力。(6)采用劲化矩形钢管核心混凝土的本构关系，利用截面网格单元法对偏压劲化矩形钢管混凝土柱试件进行数值分析，并用有限元法进行了验证，吻合良好，可以用来合理评估矩形钢管混凝土短柱的偏压承载力。更多还原

【Abstract】 The constraint role of rectangular CFST column mainly focuses in the corners, and italmost does not exist in the four central sides. So the overall confinement effect on the coreconcrete is much lower than circular CFST column. Compared with that of square CFSTcolumn, rectangular steel tubular section presents the long and short sides, so the bindingeffect of the long side on the core concrete is weaker than the short side. The long side is moresusceptible to local buckling than the short side. However, due to the presence of bindingeffect, if the setting is proper, its bearing capacity is higher than the simple uniaxialsuperposition of steel strength and concrete strength.In order to improve mechanical properties of rectangular CFST column components,binding bars (reinforcements) are set at cross section of the columns at regular intervals. Onthe one hand it can limit the lateral deformation of core concrete; on the other hand it canprovide lateral supporting effect for steel pipe, so the local buckling strength is improved. Theset of binding bars can greatly improve mechanical properties of rectangular CFST column,but area between binding bars still appears elastic-plastic local buckling phenomenon, so theconfinement role to internal filled concrete is weakened.Stiffened rectangular CFST column forms harmonious collocation by adding stiffeners tobinding bars, with minimal increase of steel consumption without increasing the difficulty ofconstruction and affecting the construction schedule. It can maximize to slow elastic-plasticbuckling between the binding bars, improve the lateral constraint ability and the mechanicalproperties of rectangular CFST column.Learning from the existing research results, the stiffening design of rectangular CFSTcolumn in the paper can achieve the higher strength, stiffness and ductility to a large extentwith thinner steel tubular wall in the premise of satisfying the structural safety of high-risebuilding. Based on the above analyses, the author has a series of researches on the mechanicalproperties of stiffened rectangular CFST column under axial load, eccentric compression, andlow cycling quasi-static loading.Specific content includes the following main aspects:(1) The tests of10square CFST columns under axial load were conducted by varying the parameters such as horizontal spacing, vertical spacing of the binding bars, the section ofstiffeners and its setting style. The paper analyzes the influence of various parameters on themechanical properties such as failure mode, stress, strain, bearing capacity and ductility,providing the basic experimental data for the following research.(2)Taking the steel tubular thickness, the diameter and strength of binding bars, the crosssection and setting style of stiffeners as parameters, low cycling quasi-static tests were appliedfor16square CFST columns specimens. The paper analyzes the hysteresis curve, skeletoncurve of each member under different parameter to calculate the bearing capacity and itsdegradation, rigidity degradation, ductility factor of displacement, energy dissipation capacity.Skeleton curve parameters of stiffened square CFST columns are determined with three linearregression analysis from the experimental results. It will provide references for the design andanalysis of the new component in the ultra-high-level engineering design and analysis.(3)The constraint mechanisms of stiffened rectangular CFST columns are analyzed. Theconstraints to concrete from the long and short sides are different. The number of binding barsand stiffeners along the long and short side is also different. Based on three axial compressioncharacteristics of core concrete, the equivalent uniaxial constitutive relationship of coreconcrete is proposed. The whole process load-deformation curves of rectangular CFSTcolumns under axial compression are calculated by the equivalent uniaxial constitutiverelationship of the core concrete. It verifies the agreement of the calculated and experimentalcurves.(4) For verifying the consistent of experiment and finite element analysis, according tothe proposed constitutive relationship of stiffened rectangular steel tubular concrete, threedimensional nonlinear finite-element analyses are conducted on all specimens. For revealingthe effects of the different setting style of stiffeners and binding bars on stress distribution ofcore concrete and steel tube, all specimens are compared. The finite-element analysis and thetest results are basically consistent. Lateral binding capacities are analyzed under the differentstiffening parameters.(5) The axial bearing capacity of stiffened structure in each style is very different, and itcannot be expressed with a uniform formula. The axial bearing capacity formula in each wayis deduced by adoption of the proposed rectangular steel tubular concrete constitutive relationship. The bearing capacities of stiffened rectangular CFST columns under axialcompression are calculated by the formula in the paper. It shows the calculations are in goodagreement with the test results and FEM analysis. Based on existing research results, themethod can reasonably evaluate axial bearing capacity of stiffened rectangular CFST column.(6) Based on the constitutive relationship of stiffened rectangular CFST concrete, meshelements’ method is presented for numerical analysis of stiffened rectangular CFST columnsunder eccentric compression, and verified with finite element method. The result shows betterconsistent. It can provide a reasonable assessment for rectangular CFST column undereccentric compression.更多还原