基于剩余刚度损伤退化的拉挤GFRP开孔板连接键疲劳性能与破坏机理研究

Pultruded GFRP profiles have numerous advantages such as: high stiffness to weight ratio, the convenience of large-scale industrial fabrication, excellent corrosion resistance. There is a broad market in the developing pre-fabricated bridge industry. Since the large thickness of GFRP plate used in bridge and other infrastructure, the big fatigue amplitude induced by the light-weighted GFRP slab when traffic load passing, the complex stress state of the joint and the complicated damage mechanism of the composite material, all these factors mix together and the fatigue performance becomes a governing issue of the structural safety. Consequently, it leads to a significant attention to the fatigue behavior of GFRP perforated connector (GPC), however, the theory or literature on the fatigue of GPC hasn’t been found yet. .Aimed on GPC in this project, the theory exploration, the experimental investigation and the numerical study will be combined. Under the fatigue loading, residual stiffness degradation considering meso-damage model will be established through the connection of meso-scale damage and macro-scale stiffness degradation. With the investigation of cyclic pull-out test and fatigue test, the failure mode of GPC will be found. The relation between GPC’s failure mode and the affecting parameters such as: stack of GFRP and radius of hole will be revealed. Based on the theoretical model and test data, an efficient method to predict the GPC’s fatigue life and damage will be proposed. The findings of this project could provide a general theoretical foundation, which solves the fatigue evaluation of GFRP connection with hole commonly used in bridge and other infrastructure.

拉挤GFRP型材轻质高强、易于大规模工业化生产、耐腐蚀，在装配式桥梁产业进程中有广泛的应用前景。由于桥梁等基建结构中采用的GFRP板材厚、且因其自重轻活载产生的疲劳应力幅显著，连接节点局部受力复杂，加之复合材料内部的微观损伤机理，这些因素聚集起来使得疲劳效应对开孔GFRP板等连接构件的结构安全至关重要，但目前尚无相关疲劳设计方法。.本项目以拉挤GFRP开孔板连接键为对象，结合理论探索、试验研究和数值计算，在疲劳荷载作用下，通过对GFRP材料细观损伤和宏观刚度退化双尺度的融合，构建剩余刚度损伤退化模型。利用循环荷载拉拔试验和疲劳试验，明确拉挤GFRP开孔板连接键疲劳破坏模式，并掌握如铺层、孔径等参数对其影响规律。基于理论与疲劳试验分析，形成对GFRP开孔板连接键的常幅疲劳寿命及疲劳损伤的高效预测方法。研究成果可为桥梁等基建结构中开孔的GFRP连接节点疲劳设计方法提供可靠的共性基础理论与依据。

拉挤型GFRP型材具有质量轻，强度高等优点，在桥梁等基础设施中有着广泛的应用前景。本课题结合试验，宏、细观理论分析和数值模拟，开展了以下研究：（1）与现有的应力集中系数相关理论，比较了双轴作用下开孔板应力集中系数随受力状态的变化；通过改变层合板的铺层方式，研究了单孔，双孔板在双轴作用下应力集中系数受层合板各向异性系数的影响关系；（2）开展了断裂力学试验，获得了拉挤型GFRP板断裂韧性等基本性能参数，并采用有限元虚拟裂纹闭合技术对断裂模式进行了研究；（3）通过细观力学公式和自编程序，构造了基于刚度退化理论的拉挤型GFRP断裂本构模型，并通过有限元模拟和第三方试验数据进行了验证，与实验结果吻合较好；（4）采用提出的基于刚度退化理论的本构模型进行了拉挤型GFRP开孔板的尺寸效应研究，进行了大量的参数化计算，得到了材料尺寸效应规律并对其抗裂性能随材料纤维体积率变化的规律开展研究；（5）开展了疲劳试验，探究了拉挤型GFRP开孔板的疲劳性能；（6）结合试验结果与数值模拟进行了单孔、双孔、单螺栓以及双螺栓的GFRP板疲劳寿命模拟，探究其疲劳寿命变化规律。