薄壁钢管混凝土异形柱抗火性能与设计研究

There exists a restriction for the application of thin-walled concrete filled steel tube column with special-shaped cross section (TCFST-SC), for the lack of fire performance results of this new kind of composite columns, therefore in this project theoretical analysis, numerical calculation and experimental research will be carried out to investigate the fire resistant behaviour and the ultimate capacity of TCFST-SC under high temperatures. The analysis on the behaviour of local buckling of the steel plates in the TCFST-SC, in high temperature, is conducted, and the influences of in-filled concrete and the stiffener are analyzed also. The mechanism of the composite columns subjected to high temperature is researched: the changing of the mechanical properties of the thin-walled steel tube, the core concrete and the stiffener, and the interaction of these three components between each other are conducted during the whole fire process. According to the lateral restraint intensity and geometric distribution of the confinement effects on the core concrete by the stiffener and steel tube gotten above, reasonable distribution of constraints are assumed, and the equivalent uniaxial constitutional relationship of confined concrete in high temperature is established. Based on the equivalent uniaxial stress-strain relationship for the encased concrete in the TCFST-SC, theoretical analysis were conducted to investigate the fire resistance of concrete-filled SHS columns in fires. Parameteric analysis was carried out to find out the main parameteres and their influnences on the fire resistant capacity of TCFST-SC columns in fires. Based on the analysis results, equations were brought up to predict the residual strength of TCFST-SC columns columns when subjected to fires. The results of this project reveals the mechanism of the TCFST-SC columns in high temperature, enhances the development and perfection of structure calculation theory of the TCFST-SC columns, and promote the usage of this new type of composite columns in our country. Thus the project has important theoretical significance and practical value.

针对缺乏薄壁钢管混凝土异形柱抗火性能研究成果制约其推广应用的问题，本项目以理论分析、数值计算与试验研究有机结合的方法开展系统研究：研究高温下薄壁钢管混凝土异形柱钢管管壁局部屈曲机理与规律，探索内填混凝土与加劲肋设置对其影响；研究高温下组合柱受力机理，分析受火全过程中薄壁钢管、核心混凝土以及加劲肋力学性能的变化，得到三者相互作用的规律；根据所得的核心混凝土所受侧向约束强弱及几何分布规律，假定约束的合理分布，推导核心混凝土高温下等效单轴受压本构模型；基于所建立的本构关系，建立薄壁钢管混凝土异形柱抗火性能分析模型并编制数值程序，分析影响组合柱耐火极限的主要因素及其影响规律，并据此提出薄壁钢管混凝土异形柱抗火性能的设计方法与设计建议。本项目成果揭示高温下薄壁钢管混凝土异形柱的受力机理，对发展和完善薄壁钢管混凝土柱异形结构计算理论，促进该种新型组合构件在我国的进一步推广应用具有重要的理论意义和实用价

针对带加劲肋薄壁钢管混凝土异形柱抗火性能进行研究，进行了16根恒高温下带肋薄壁钢管混凝土轴压短柱试验，主要考察钢筋加劲肋的设置与否及温度对此类薄壁钢管混凝土短柱的极限承载力、弹性模量和延性的影响，记录了试件达到指定温度时的破坏模式和荷载-位移关系曲线。进行了12根高温下带肋薄壁钢管混凝土中长柱耐火性能试验，考察参数包括：截面形式（方形和T形）、加劲肋间距、轴压比和荷载偏心距，量测了构件的温度分布和轴向变形，获得了带加劲肋薄壁钢管混凝土异形柱的破坏模式。整理分析了已有的钢材和混凝土的材料热力学模型，在合理选择材料本构关系的基础上，基于ABAQUS有限元建立恒高温下方形、T形薄壁钢管混凝土轴压短柱的力学分析模型，并用本课题组试验及相关的钢管混凝土柱的试验验证了模型的正确性，利用该模型分析了钢筋加劲肋尺寸、钢筋加劲肋纵向间距、构件截面含钢率、构件截面尺寸和温度等参数对试件力学性能的影响规律。利用能量法求解了外包钢板常温下的局部屈曲临界荷载和热屈曲临界温度变化值，在此基础上进行了方钢管混凝土短柱在纵向荷载和温度变化共同作用下外包钢板的局部屈曲分析。