【作者】 王二磊；

【导师】 卢哲安；

【作者基本信息】 武汉理工大学 ， 桥梁与隧道工程， 2012， 博士

【摘要】 目前国内外关于钢管混凝土的研究主要集中在圆形和矩形钢管混凝土,对异形钢管混凝土的研究还较少。异形截而钢管混凝土具有截而形式灵活、节点构造多样及抗震性能好等优点,在工程中已被逐渐应用。武汉后湖大桥采用单索而非对称独塔圆端形钢管塔柱,是一种创新型结构形式。针对圆端形截而钢管混凝土构件,如何计算其承载力,进行结构设计,最基本、最可靠的研究工作是通过模型试验来研究该类构件的力学行为,结合理论分析对比,校正模型,弥补试验数据不足的缺陷,从而为结构设计提供依据。本文依托武汉后湖大桥工程实际,通过圆端形钢管混凝土轴压试验、偏压试验及有限元分析,系统研究了圆端形钢管混凝土抗压力学性能,进而基于可靠度理论,利用ANSYS可靠度分析模块,对圆端形钢管混凝塔柱可靠度进行了分析。本文进行的主要工作和取得的成果有：第一,基于工程实际,进行大尺寸圆端形截而钢管混凝土试件轴心受压试验、偏心受压试验,轴压试验表明：轴向荷载作用下,圆端形钢管混凝土试件具有较好的承载能力,但由于角部应力集中,套箍效应引起的试件强度提高有限；套箍力分布不均匀,其在钢管壁的分布与钢管形状有很大关系；由于本试件套箍系数较小,钢管对核心混凝土的约束不大,试件破坏整体表现出脆性破坏的特征。偏压试验分析表明：偏心率是影响试件偏心受压力学性能的主要因素,随着偏心距的增大,承载力不断降低：在偏心距较大的工况下,试件荷载-横向位移曲线弹性工作阶段较短,承载能力降低较多；极限荷载作用下,圆弧与直线段交接处钢管焊缝首先开裂,试件破坏时,钢管受压区边缘已达到屈服,而另一侧尚处于弹性受拉阶段。第二,在试验的基础上,对圆端形钢管混凝土轴心受压及偏心受压进行了有限元模拟。研究表明：摩擦系数的变化对圆端形钢管混凝土试件的轴心受压承载力影响很小；核心混凝土的强度对钢管混凝土轴压承载力提高影响不大；钢材强度对轴心受压试件弹塑性影响较大；相同含钢率的情况下,钢材的强度越大,圆端形钢管混凝土轴心受压的承载力越高,试件的延性越强。对于圆端形钢管混凝土偏心受压试件,随着长细比的增加,圆端形钢管混凝土的承载力降低,弹性工作阶段缩短,而弹塑性工作阶段延长；随混凝土强度的增大,相对屈曲系数逐渐变小；随着钢材强度增大,试件承载力不断提高,但承载力提高趋势趋缓；随着钢管壁厚增加,试件的承载力越高,延性增强。第三,基于统一理论,结合试验及有限元模拟,拟合得到适合于圆端形钢管混凝土轴心受压、偏压试件的承载力计算公式,并将公式计算结果与试验结果及有限元分析结果进行对比,吻合良好。第四,基于可靠度理论及ANSYS可靠度分析模块,对后湖大桥圆端形钢管混凝土塔柱,采用蒙特卡洛法和响应面法进行可靠度分析。研究表明：对于以应力作为输出控制指标的可靠度计算而言,抗拉强度满足要求的结构可靠度为98.69%,抗压强度满足要求的结构可靠度为98.89%。上述分析表明,有限元理论与可靠度理论的有机结合,可应用于复杂结构的可靠性分析。对于圆端形这种特殊截面钢管混凝土,本文给出了大量首次发表的研究成果,揭示了圆端形钢管混凝土受压力学特性,系统分析了圆端形钢管混凝土塔柱可靠度,其研究结果为圆端形钢管混凝土的进一步研究和工程应用提供了重要的理论依据。更多还原

【Abstract】 Research of CFST mainly in square and rectangular sections at home and abroad, specially shaped CFST is less. The advantages of specially shaped Steel Tube-Filled Concrete (CFST) are flexible section form, diverse node constructor and good seismic performance, which have been has been gradually applied in engineering. A large size round-ended CFST tower with single cable plane was used in Houhu Bridge in Wuhan, which is an innovative structure. For round-ended CFST design, how to calculate bearing capacity, the most basic and reliable research work is to study mechanical behavior through model experiment, combined with theoretical analysis to make for experimental data, and thus provide basis for structure design.Based on Houhu Bridge project, compressive mechanical properties of round-ended CFST are studied through axial compression experiments, eccentric compression experiments and finite element analysis. Based on reliability theory, reliability of round-ended CFST tower is studied by reliability analysis module of ANSYS. The main work and achievements in the article are summarized as following:Firstly, based on engineering practice, axial compression experiments and eccentric compression experiments of large sized round-ended CFST are carried out to study compressive mechanical behavior of round-ended CFST. Results show that:round-ended CFST under vertical load with good carrying capacity, but because corner stress concentration, bearing capacity improvement by stirrups effect is limited. Circumferential force distribution within the tube is uneven, which has great relation with tube shape. Because stirrups effect of steel tube on core concrete is small, component damage overall demonstrates the obvious fragility characteristic performance. Eccentric compressive experiment shows that eccentricity is major factor to affect bearing capacity. With increasement of eccentricity, bearing capacity will decrease. For large eccentricity conditions, load-lateral displacement curve of elastic stage is short and bearing capacity reduces much. Under ultimate load, steel tubular welded joint dehiscence at circular arc and tangential interface point, steel tublar compression zone have reached yield, while the other side is still in elastic stage.Secondly, based on experiments, round-ended CFST compressive mechanical properties are studied by finite element simulation. Finite element simulation shows that friction coefficient has little effect on round-end CFST bearing capacity. Core concrete strength has significant influence on component elastic-plastic properties. In the case of the same steel ratio, for round-ended CFST under axial compression, the greater of steel strength, the greater of bearing capacity, the stronger of component ductility. For round-ended CFST under eccentric compression, as the slenderness ratio increases, bearing capacity reduce, elastic stage shortens, but elastic-plastic stage extend. As concrete strength increase, the relative buckling coefficient gradually becomes smaller. As steel strength increase, bearing capacity increase, but rising slope slower gradually. As tube thickness increase, bearing capacity increase.Thirdly, based on unified theory, combined with experiment and finite element simulation analysis, bearing capacity formula of round-ended CFST under axial compression and eccentric compression are summarized, and the formula results compared with experiment data and finite element simulation results show results are in good agreement.Fourthly, based on reliability theory and reliability analysis module of ANSYS, round-ended CFST tower reliability of Houhu Bridge is systematically studied by Monte Carlo method and response surface method. Study shows that:for the control indicators of stress as the output reliability calculation, tensile strength to meet the requirements of structural reliability is98.69%, compressive strength to meet the requirements of structural reliability is98.89%. Analysis shows that the integration of finite element theory and reliability theory can be applied to complex structural reliability analysis.For round-ended CFST, the article gives a large number of first publication research results, which reveal round-ended CFST compressive mechanical properties, and systematic analysis round-ended CFST tower reliability. The research provides theoretical foundation of round-ended CFST further study and engineering application.更多还原