负载下轴心受压钢柱外包钢筋混凝土加固的力学机理及设计方法研究

With widely application of steel structure in China, people are paying increasing attention on the reinforcement technique of steel structure and its components. However, currently traditional reinforcement methods of steel structure are difficult to thoroughly consider affecting factors involving corrosion, fire protection and welding heat, and most steel structure reinforcement is performed under load. This project proposes a research on composite reinforcement technique of axially compressive steel column strengthened with enclosed reinforced concrete. The reinforced structure form is equipped with the advantages of both steel and concrete structure, with high bearing capacity, stability, corrosion and fire resistance characteristics. First of all, the reinforcement experiment of axially compressive steel column under different initial compressive load is tested, and the project systemically studies the stress redistribution rule of different materials and stress states on steel column after load reinforced, and analyzes mechanical properties and failure characteristics of members after reinforcement. Then, the finite element numerical model which accurately takes every parameter like initial load into consideration is established. Eventually the researchers consider the role of load, introduce strength reduction factor of material and propose design method and construction technological process. The research achievements of this project can correctly guide more reinforcement design. Also it will provide technical support for compiling national standards ‘Technical specification for strengthening steel structures’ (GB).

随着钢结构在我国的广泛应用，钢结构及其构件加固技术日益引起重视，而目前钢结构构件传统加固方法难以全面考虑腐蚀、防火及焊接热等影响因素，且大多钢结构加固是在负载下进行的。本项目提出负载下轴心受压钢柱外包钢筋混凝土组合加固技术研究，加固后的结构形式兼备钢结构和混凝土结构的优点，具有承载性能和稳定性高、防腐及防火性好等特点。项目首先针对不同负载作用的轴心受压钢柱进行加固试验，系统研究钢柱负载加固后的不同材料不同应力状态的应力重分布规律、分析加固后构件受力机理及破坏特征；然后建立准确考虑初始负载等参数的有限元数值模型；最后考虑负载作用，引入材料强度折减系数，提出设计方法及施工工艺流程。本项目的研究成果可以正确指导更多的加固设计工作，也为正在编制的国家标准《钢结构加固技术规范》(GB)提供技术支撑。

随着钢结构在我国的广泛应用，钢结构及其构件的加固技术日益引起广泛重视，本课题提出负载下轴心受压钢柱外包钢筋混凝土组合加固技术研究，加固后的结构形式兼备钢结构和混凝土结构的优点，具有承载性能和稳定性高、防腐及防火性好等特点。课题首先通过轴心受压钢柱完全卸载情况下和负载情况下的加载试验和轴心受压钢柱负载下外包钢筋混凝土加固的加载试验，研究了型钢受力过程中应力的分布模式，负载下外包钢筋混凝土加固试件的受力性能和应力重分部规律以及影响参数。试验结果表明：外包钢筋混凝土的加固方法可以显著提高原钢构件的承载能力和刚度；加固后构件的极限承载力随着初始负载的增大而降低；随着混凝土强度和型钢强度的提高而增大。之后通过引入生死单元技术，建立了负载下轴心受压钢柱外包钢筋混凝土加固的ABAQUS有限元模型，通过有限元分析结果与试验结果的对比分析，验证了此有限元模型的准确性和可靠性，在此基础上，利用此有限元模型进行了有限元参数分析。最后，在试验研究的基础上，通过分析加固时和破坏时加固构件各部分的应力应变状态，推导出了能够综合考虑初始负载、混凝土强度等级、型钢强度等级以及箍筋约束作用的负载下轴心受压钢柱外包钢筋混凝土加固的承载力计算方法。并将承载力公式的计算结果与试验结果进行了对比分析，验证了此计算公式的准确性。