FRP型材-混凝土板桁组合梁节点连接静力失效与疲劳断裂机理研究

Adequately utilization of the special mechanical characteristics of pultruded FRP (Fiber Reinforced Polymer) can be obtained through reliance on the innovative FRP-truss-concrete-deck hybrid beam. However, significant improvement on the capacity of joints is the foundation of wide application of this system in highway bridges..Two primary scientific points, regarding to failure mechanism and fatigue fracture mechanism of joints, are focused on in this project. Static and fatigue tests on pultruded FRP plates and profiles will be carried out to investigate the macro mechanical performance as well as the failure process in a micro scale level. Numerical analysis will be performed to obtain optimal joint types based on micro-mechanical model with various joint parameters. Finite element simulation of fatigue test of FRP joints will be executed to quantify the relationship of crack propagation rate and the stress intensity factors amplitude and subsequent prediction method on fatigue life and measurements on improving fatigue performance will be put forward. Innovative connection technique with high capacity and superior fatigue performance will be developed and joints design philosophy will be proposed based on macro mechanical performance..Failure mechanism and fatigue fracture of pultruded FRP joint will be illustrated in a micro scale level with the combination of macro mechanics theory. This project is a fundamental research on new bridge systems and new components using high performance composites.

FRP型材-混凝土板桁组合梁可巧妙发挥拉挤型材力学特点，欲使其应用在公路桥梁中，须大幅提高节点连接的承载能力和疲劳性能。.项目围绕FRP拉挤型材节点连接静载失效、疲劳断裂的细观机理与提高机制等关键科学问题，进行FRP拉挤板、型材连接节点的静力和疲劳试验，测试宏观力学性能，并进行破坏过程的细观层面跟踪观测。进行FRP型材节点连接静力细观尺度数值模拟和细观力学分析，优化节点构造与连接参数。进行疲劳试验和细观尺度有限元模拟，研究FRP型材裂纹扩展速率和应力强度因子幅值的关系，提出节点疲劳寿命预测方法和耐疲劳性能提高对策。基于“预紧栓齿连接技术”与“铺层加强工艺”融合，研发大承载、耐疲劳连接技术，将细观力学原理和宏观力学方法结合，提出其设计方法。.项目从细观尺度揭示FRP拉挤型材连接节点的静力失效、疲劳损伤和断裂等基本规律，并与宏观力学方法联系，属高性能复合材料新型桥梁体系和新型构件的基础研究。

FRP型材-混凝土板桁组合梁是通过带界面剪力键的FRP上弦杆或特殊节点与混凝土桥面板相结合形成的新型结构体系，合理的节点连接技术是该结构体系得以实现的核心问题。项目开展了FRP型材-混凝土板桁组合梁节点连接静力失效与疲劳断裂机理研究，围绕FRP型材连接失效机理、FRP型材-混凝土界面连接失效机理、新型大承载FRP拉挤型材桁架节点连接技术及其设计方法等方面展开了系统研究，取得了创新性成果：.（1）运用复合材料经典理论、精细化数值模拟及拉挤型材桁架节点试验研究，揭示了FRP型材连接节点的渐进失效机理；.（2）揭示了FRP型材-混凝土板界面连接的失效机理，系统分析了主要设计参数对于FRP型材-混凝土板界面连接破坏模式、抗滑移刚度、极限承载力的影响；.（3）提出了适用于桥梁结构的大承载FRP拉挤型材桁架节点连接形式，建立了新型节点连接设计方法。.经过四年的研究，项目实现了既定目标，在《Journal of Composites for Construction, ASCE》、《Engineering Structures》、《Composites Structures》等国际权威期刊，以及《建筑结构学报》、等国内工程领域顶级期刊发表高质量论文15篇，其中SCI收录11篇，EI收录2篇，授权国家发明专利3项，人才培养成效显著。该项目聚焦于FRP型材-混凝土板桁组合梁节点连接性能研究，在国内开辟了一个新的研究方向，与UC Davis等世界知名高校展开合作，并在多场国际学术会议做报告，在国内外产生了较大的影响。