高性能矩形钢管混凝土柱协同工作组合力学性能研究

High-performance CFRT (Concrete-filled Rectangular Steel Tube) column combines the technologies of both self-compacting micro expansion concrete and CFRT. It has the advantages of higher bearing capacity, good ductility, simple connection and fire prevention measures. It also can achieve the goals of both energy conservation and emission reduction in the construction. Therefore, High-Performance CFRT column has a promising application prospect in engineering. With its excellent section form, CFRT has been widely used in high-rise building. However, the mechanical property of CFRT is influenced significantly by the cooperation mechanism between the steel and the concrete. Research on the cooperation mechanism of High-Performance CFRT column is still lack as it results the mechanical property of High-Performance CFRT is not clear. Besides, the prediction accuracy of the existing international specification for the bearing capacity of High-Performance CFRT column is needed to be improved. Theoretical derivation, experimental research and mesoscopic numerical simulation analysis will be adopted as research methods in this project. First, the mesoscopic simulation model will be set up, and its correctness will be verified by both push-out tests and eccentric loading tests. Thus, the technical problem for determining interface stress will be solved. The interface bond–slip surface model and interface bond strength calculation formula will be derived，and the construction measures for achieving the optimal mechanical properties will be put forward. Besides, the section stress development rule will be further explored. The finite element method, with a linear strain distribution on the whole section, will be improved and the eccentric loading bearing capacity formula for High-Performance CFRT column will be derived at last. In conclusion, the results of this project can make a theoretical basis for the extensive application of High-Performance CFRT column into the practical engineering.

集自密实微膨胀混凝土与矩形钢管混凝土技术于一体的高性能矩形钢管混凝土柱具有承载力高、延性好、节点制作方便、防火措施简便等优点，可实现建设节能减排的目标，在建筑工程中具有广阔应用前景。然而，矩形钢管混凝土组合力学性能受钢管与混凝土协同工作机理影响显著，目前尚缺乏关于高性能矩形钢管混凝土柱协同工作机制的研究，且现有国内外规程对其承载力的预测精度有待提高。基于此，本项目拟采用试验研究、细观数值仿真分析和理论推导相结合的方式，建立钢管混凝土细观数值仿真模型，利用宏观试验验证细观模型的正确性，从而解决全截界面应力难以测定的技术难题，建立全截界面粘结-滑移曲面模型与界面粘结强度计算公式，提出实现最优力学性能的构造措施；探索截面应力发展规律，改进以全截面线性应变假定为基础的纤维单元分析法，推导高性能矩形钢管混凝土柱偏压承载力计算公式，为其在实际工程中的推广应用奠定理论基础。

本项目采用试验研究、细观数值仿真分析、数值分析和理论推导相结合的方式，对集自密实微膨胀混凝土技术和矩形钢管混凝技术于一体的高性能矩形钢管混凝土柱的协同工作机制进行研究。首先,为了研究钢与混凝土界面粘结性能，进行了高性能矩形钢管混凝土柱的推出试验，分析不同影响因素对构件粘结强度的影响，掺加膨胀剂与合理设置栓钉均可有效提高钢与混凝土界面粘结性能，结合试验数据及已有文献中的数据分析得到了考虑不同膨胀剂掺量、混凝土强度及长厚比的高性能方矩形钢管混凝土柱的界面粘结强度计算公式，并推导了四折线界面粘结滑移模型表达公式。之后建立钢管混凝土细观数值仿真模型，对比宏观推出试验荷载位移曲线验证细观模型的合理正确性，揭示全截界面粘结应力发展规律；其次，进行了钢管混凝土柱的轴压性能数值分析，对比分析现有规程对轴压承载力预测的精确度，探讨现有矩形钢管混凝土柱的两种轴压力分配系数公式的可靠性；进行了基于界面损伤的高性能矩形钢管混凝土柱的轴压承载力试验研究与界面无损伤构件的轴压性能数值分析，通过数值分析得到了钢管对混凝土接触应力沿构件长边及短边的分布规律，对比研究了界面损伤对构件轴压承载性能的影响规律，得到推出试验虽然破坏了构件的界面承载力，但此种界面损伤对于构件轴压承载能力的影响可以忽略不计的结论；之后，进行了高性能矩形钢管混凝土柱的偏压试验研究与参数化数值模拟，探索截面应力发展规律，对比分析现行规范及数值模拟对单向偏压构件P-M曲线的预测值与实测值，有限元和规范EC4、规范CECS159:2004的计算结果较为安全准确，而规范LRFD过于保守。提取大量现有文献中的试验数据与上述规范中的轴压、纯弯、压弯承载力公式计算结果进行对比，提出针对不同影响因素合理选择较为适用的规范的建议，为指导高性能矩形钢管混凝土柱在实际工程中的设计及推广应用提供理论基础。