【作者】 杨帆；

【导师】 高飞；

【作者基本信息】 华中科技大学 ， 结构工程， 2022， 博士

【摘要】 高强度钢材钢结构具有承载力高、截面尺寸小、用钢量少、经济性好、绿色环保等特点,但使用高强度钢材的构件通常较为细长和轻薄,失稳更为突出。对此,本文采用抗扭刚度较高的闭合钢管混凝土翼缘代替普通工字形截面梁的开口薄壁上翼缘,形成一种具有良好稳定性能的新型高强度钢材组合截面梁——矩形高强钢管混凝土翼缘工字形梁。这种新型构件承载力高、稳定性好,具有较高的工程应用价值。鉴于相关研究有限,本文综合试验研究、数值模拟和理论推导等方法系统地研究了矩形高强钢管混凝土翼缘工字形梁的受弯性能与设计方法,主要内容如下:(1)开展了6个矩形高强钢管混凝土翼缘工字形梁在无侧向约束跨中集中荷载作用下的受弯性能静力试验,得到了强度破坏和整体失稳破坏两种不同破坏模式下试件的变形特征、应变发展规律和承载能力。结果表明,将工字形梁的上翼缘替换为钢管混凝土翼缘能有效提升整体稳定性。(2)通过有限元软件建立了考虑高强度钢材力学性能、初始几何缺陷和稳定问题的矩形高强钢管混凝土翼缘工字形梁三维非线性有限元模型,并基于试验结果验证了有限元方法的正确性,随后开展了参数分析,得到了跨度、初始几何缺陷、加劲肋、几何尺寸、钢材和混凝土等参数对其受弯强度和整体稳定性能的影响规律。(3)开展了矩形高强钢管混凝土翼缘工字形梁截面应力应变分析和弹性整体屈曲分析,推导了边缘屈服弯矩、塑性极限弯矩和弹性侧向弯扭屈曲临界弯矩的计算公式;基于试验研究、数值模拟和理论推导结果,结合现有钢结构设计标准,提出了受弯强度和整体稳定性设计方法,其预测结果与有限元结果比值的均值和变异系数分别为1.001和4.28%。(4)开展了矩形高强钢管混凝土翼缘工字形梁腹板弹性剪切屈曲分析,推导了腹板弹性剪切屈曲临界剪应力计算公式;基于有限元模型分析了矩形高强钢管混凝土翼缘工字形梁的局部稳定性能,研究了钢管混凝土翼缘、横向加劲肋、初始几何缺陷和钢材强度在不同腹板宽高比和高厚比下对局部屈曲后受剪承载力的影响;结合理论、有限元和现有钢结构设计标准,提出了局部稳定性设计方法,并通过与数值结果的对比验证了其可靠性。更多还原

【Abstract】 High-strength steel structures have many advantages,such as higher bearing capacity,smaller section size,less steel consumption,economic and environmentally friendly.However,structural components made by high-strength steel tend to be slender and thin,so they are more prone to stability problems.To solve this problem,this paper proposed a new type of high-strength steel composite beams with good stability performance,named rectangular concrete-filled tubular flange high-strength I-beam(RCFTFHSIB),in which the open thin-walled plate top flange of traditional I-section beams was replaced by the closed rectangular concrete-filled steel tube with high torsional rigidity.This new type of composite beam has high bearing capacity and good stability,and it hence has high engineering application value.Considering the research on it still remains scarce,this paper systematically studied the flexural behavior and design method of RCFTFHSIBs by means of experimental investigation,numerical simulation,and theoretical derivation.The main contents are as follows:(1)A total of 6 flexural behavior tests on RCFTFHSIBs were conducted under lateralunrestrained mid-span concentrated load.The deformation characteristics,strain developments and capacity of RCFTFHSIBs with the failure modes of flexural yielding and lateral-torsional buckling were explored.The results indicated that the lateral-torsional buckling resistance of I-beams could be effectively improved by replacing the top flat flange by concrete-filled tubular flange.(2)Three-dimensional nonlinear RCFTFHSIBs finite element(FE)models were established by using commercial FE software.The FE models considered material properties,initial geometric imperfection and instability,and were carefully validated against test results.The validated FE models were then used to carry out a comprehensive parametric study to investigate the influences of several parameters on the flexural strength and lateral-torsional buckling behavior,such as span length,initial geometric imperfections,number of stiffeners,geometric dimensions,steel grades and concrete grades.(3)Section stress and strain analysis and elastic buckling analysis were performed,and the calculation method of yielding moment,full plastic moment and critical elastic lateraltorsional buckling moment of RCFTFHSIBs were proposed.Based on the theoretical,experimental and numerical results,together with current design specifications of steel structures,the design method of flexural strength and lateral-torsional buckling strength of RCFTFHSIBs was developed.The mean value and coefficient of variation of the predictionto-resistance ratio are 1.001 and 4.28%,respectively.(4)The elastic shear buckling analysis were carried out,and the formula for calculating the critical elastic shear buckling stress of the web of RCFTFHSIBs was derived.The postbuckling shear resistance of RCFTFHSIBs was investigated based on the validated FE models,and the effects of flange dimensions,number of stiffeners,initial geometric imperfections,and steel grades on the post-buckling shear behavior of RCFTFHSIBs under different width-to-height ratio and width-to-thickness ratio of webs were studied.Based on the theoretical and numerical results,together with current design specifications of steel structures,the design method of shear strength of RCFTFHSIBs was developed,and the reliability of the design equations is verified by the comparison with the numerical results.更多还原