【作者】 杜喜凯；

【导师】 王铁成；

【作者基本信息】 天津大学 ， 结构工程， 2010， 博士

【摘要】 随着组合结构的发展,方钢管混凝土结构在高层建筑中的应用不断增加,其抗震性能的研究也越来越引起人们的关注。尽管国内外学者在方钢管混凝土抗震性能方面做了大量的研究工作,但对方钢管混凝土构件材料的本构关系的研究还很不充分。本文通过9个方钢管混凝土柱在低周反复荷载作用下的试验,系统的研究了方钢管混凝土柱材料的本构关系和抗震性能,主要进行了以下几个方面的工作。分别以轴压比n、长细比λ和套箍系数ξ为参数,对9根方钢管混凝土柱在低周往复荷载作用下的滞回性能进行了试验研究。试验得到的P-Δ(荷载-位移)滞回曲线图形饱满,没有明显的捏缩现象出现,表现出良好的耗能能力。试验柱位移延性系数μ随轴压比n的增大而降低;随长细比λ增大,延性系数μ降低;随套箍系数ξ增加,延性系数μ增大。采用非线性有限元程序ABAQUS对轴心受压方钢管混凝土柱进行了计算,分析了混凝土强度f_c、截面宽厚比B /t和钢材强度f_y对钢管和核心混凝土纵向应力-应变曲线的影响规律,提出了方钢管混凝土柱钢管和核心混凝土的等效单轴受压应力-应变关系曲线的计算公式。应用本文提出的等效单轴受压应力应变曲线,采用DRAIN-2DX中的纤维梁柱单元,对方钢管混凝土柱在往复水平荷载作用下的滞回性能进行了计算分析,以套箍系数ξ、轴压比n和长细比λ为参数,计算了124根方钢管混凝土柱。通过对计算结果的分析,建立了方钢管混凝土柱的P-Δ滞回模型。对试验的方钢管混凝土柱滞回耗能进行了分析,采用基于能量耗散原理和构件滞回特性建立的累积损伤模型,对往复荷载作用下方钢管混凝土柱累积损伤进行了计算分析。计算结果表明当试件翼缘发生鼓曲时累积损伤指标在0.6～0.7左右,破坏时累积损伤指标在0.8～0.9之间。更多还原

【Abstract】 With the development of composite structures, the use of square concrete-filled steel tube (CFT) in high-rise buildings has been increasing. The seismic behavior of square CFT is being paid more and more attention to by researchers. Even though a lot of studies on the seismic behavior of square CFT have been made in the world, it is still insufficient in research on the constitutive relation for CFT material. In this paper, the constitutive relation for CFT material and the seismic behavior of square CFT beam-columns are investigated by testing nine specimens under a constant axial load and cyclically varying lateral load. The main work is summarized as follows.Nine specimens are tested for the study of the hysteretic behavior of square CFT beam-columns under cyclic loading with the main parameters being axial loading level n , slenderness ratioλand confinement indexξrespectively. The load-displacement (P-Δ) hysteretic curves of the specimens tested are plump in shapes, and have no significant pinch phenomenon, which indicate that square concrete-filled steel tube column has high energy dissipation capacity. The ductility factor of the specimens decreases with the increase of the axial compression ratio and the slenderness ratio, and increases with the increase of the confinement index.Square CFT columns are modelled under axial compression loading using nonlinear finite element programme ABAQUS. The effect of concrete compression strength f_c, section width-to-thickness ratio B/t and steel yield stress f_y on the effective stress-strain relationship for the steel tube and concrete infill is analyzed to develop an equivalent uniaxial compression stress-strain relationship mathematical equation of steel tube and concrete infill.Fiber-based beam-columns element in DRAIN-2DX, with the equivalent uniaxial compression stress-strain relationship of steel tube and concrete fibers suggested in this paper, is employed to calculate P-Δhysteretic relationship of CFT beam-columns under a constant axial load and cyclically varying lateral load. A hundred and twenty-four CFT beam-columns are analyzed with the parameters including confinement indexξ, axial loading level n and slenderness ratioλ. Based on the analysis results, the simplified model of P-Δhysteretic relationship of CFT beam-columns is developed.Absorbed hysteretic energy at each cycle is analyzed for the experimental specimens. The cumulated damage model based on the theory of energy dissipation and hysteretic behavior is employed to evaluate the damage index for square CFT beam-columns under cyclic loading. The results show that the damage indices of the specimens range between 0.6 and 0.7, as the flange of the specimen bulged, and between 0.8 and 0.9, as the specimen damaged entirely.更多还原