基于尺寸效应的足尺钢管高强混凝土柱耐火性能研究

Fire of high-rise building increased quickly year by year with the rapid development of high-rise building in China. With high load-bearing capacity and construction convenient, high strength concrete filled steel tube columns were a widely used construction form in high-rise building constructions. Based on test results of materials and structural members of small size, the general fire resistance design approach was obtained. Considering the influence of size effect, the theory was quite unreliable by a lack of mechanical properties of full-scale structures. The size effect of materials and structural members had a great influence on fire resistance performance of high strength concrete filled steel tube columns under combined temperature and compressive loading, however, the fire resistance performance of full-scale high strength concrete filled steel tube columns under compressive loading were not available at present. According to experimental research and theoretical analyses, the fire resistance performance tests of full-scale high strength concrete filled steel tube columns under compressive loading were investigated. The mechanism and influencing factors of fire resistance of high strength concrete filled circle and square steel tube columns under axial compression and eccentrically compression were studied in detail. Considering fire exposure and size effect, the compression mechanism of high strength concrete filled steel tube columns were investigated. Based on systematical parametric analysis of test results, a simplified calculation method was developed for full-scale high strength concrete filled steel tube columns. According to size effect influence of materials and structural members, the method of specific mechanical model was proposed with fire-damaged effect on fire resistance of high strength concrete filled steel tube columns. The results of this research would lay the foundations for fire resistance design of high strength concrete filled steel tube columns.

随着高层建筑日益增多，高层建筑火灾呈逐年上升趋势。钢管高强混凝土柱以其承载力高，施工方便等优点，在高层建筑中得到了越来越多的应用。基于小尺寸范围的材料和构件破坏试验成果建立起来的设计理论是普遍采用的抗火设计方法，该方法缺乏考虑尺寸效应对结构力学性能的影响，难以保证结构的可靠性。钢管高强混凝土柱抗压性能受尺寸效应影响较大，然而，关于尺寸效应对受压足尺钢管高强混凝土柱耐火性能的影响，国内外还鲜有报道。本项目拟采用试验研究和理论分析相结合的方法，进行受压足尺钢管高强混凝土柱耐火性能试验研究，分析轴心和偏心受压圆形和方形钢管高强混凝土柱耐火性能受力机理及其影响因素，揭示火灾作用和尺寸效应对其受压性能的影响规律。在对试验结果进行系统的参数分析基础上，提出具有明确力学模型的，能够反映材料和构件尺寸效应对轴心和偏心受压钢管高强混凝土柱耐火极限影响规律的简化计算方法，为钢管高强混凝土柱抗火设计奠定基础。

钢管混凝土柱广泛应用于高层和超高层建筑结构中，柱内通常采用高强混凝土材料并且截面尺寸相对较大。由于钢管位于混凝土的外部，在火灾中可能直接受到高温的作用，研究相对较大尺寸的钢管高强混凝土柱的耐火性能对于此类结构的应用具有重要的工程意义。.本项目以足尺的圆形截面和方形截面钢管高强混凝土柱结构为研究目标，有针对性的开展了系列模型试验、有限元模拟及理论分析工作，以期准确确定钢管高强混凝土柱的耐火性能，解决火灾下钢管高强混凝土柱的耐火性能无法满足规范和工程需求的问题。项目的主要工作及成果如下：.（1）完成了标准升温曲线作用下，12根钢管高强混凝土柱的耐火性能试验。模型设计中考虑了截面形式、荷载类型、防火保护方式及轴压比等参数变化，系统分析了试验模型的温度场、耐火极限、变形-时间关系、破坏形态等关键性能指标，探讨了各设计参数对钢管高强混凝土柱耐火性能的影响规律。.（2）基于试验结果，采用ABAQUS有限元分析软件建立模拟模型，将模拟结果与试验结果进行对比验证，确定有限元模型的有效性。基于试验验证的有限元模型，通过参数分析，将试验未涵盖的参数取值进行补充分析，明晰不同参数变化对钢管高强混凝土柱耐火性能的影响规律。.（3）在试验研究和有限元模拟的基础上，根据参数分析影响规律的结论，采用了数值拟合方法，理论计算公式选取对于钢管高强混凝土柱耐火极限和火灾下受压承载力重要的影响因素，提出了钢管高强混凝土柱耐火极限和火灾下受压承载力的简化计算方法。.（4）完成了标准升温曲线作用后，8根钢管混凝土叠合短柱的轴压承载力试验，通过截面形状、钢管尺寸和长细比3个参数的变化，对钢管混凝土叠合短柱的破坏模式、轴压强度和轴向刚度等指标进行了分析。采用ABAQUS有限元分析软件建立模拟模型，基于试验验证的有限元模型，开展了参数分析，提出了受火冷却后叠合短柱轴压极限承载力和轴向刚度简化计算方法。.上述研究为钢管高强混凝土柱结构的应用奠定了基础。