湿热环境下CFRP加固受损钢结构的疲劳裂纹扩展规律研究

The degradation of adhesive bonding in a hygrothermal environment may have a significant adverse effect on the fatigue behaviour of cracked steel structures strengthened with externally bonded CFRP. This project will conduct a theoretical, numerical and experimental study on centrally notched steel plates and beams with two notches in the tensile flange strengthened by CFRP plates. It aims to develop an assessment method of fracture toughness of the bond interface in CFRP strengthened steel structures degradated in a hygrothermal environment, from its results a model of degradation of the adhesive bond will be developed.The project will also develop a method for assessing the fatigue damage in the steel structure and the bonding interface, aiming to quantify the relationship between the damage of adhesive bond including debonding and fatigue crack propagation. Based on the mechanical model and finite element procedures developed to analyze the fatigue behaviour of CFRP strengthened cracked steel structures subject to hygrothermal environment, a method for predicting the fatigue life of FRP strengthened steel structures with deficiency will be given. The theoretical and experimental results will be used to develop design recommendations for strengthening steel structures with CFRP, improve the science base for upgrade and rehabilitation of steel bridges and crane structures. The output of the project should provide important scientific insights as well as significant practical applications.

湿热环境下界面粘结性能的退化将对CFRP加固带裂纹钢结构的疲劳破坏机理产生显著影响。本项目以CFRP加固的带圆孔钢板和受拉翼缘带缺口的工字钢梁为研究对象，采用理论分析、数值模拟和实验研究相结合的方法，建立湿热环境老化后CFRP加固钢结构粘结界面的断裂韧度评估方法，揭示湿热循环下界面粘结性能的退化规律；提出钢结构及粘结界面疲劳损伤的有效测试方法，明确粘结界面损伤和剥离与钢结构疲劳裂纹扩展的关系；建立CFRP加固带裂纹钢结构疲劳破坏的力学分析模型和数值模拟方法，提出加固构件在湿热环境下的疲劳寿命预测方法。本项目的完成，将为制定CFRP加固钢结构的设计和施工规范，为钢桥和吊车梁等承受疲劳荷载构件的加固维修，为新材料、新技术和新构件的开发等提供理论依据和实验数据。预期的成果既有重要的科学意义，又有广阔的应用前景。

利用轻质、高强和耐腐蚀的CFRP材料进行表面粘贴可快速、安全地修复受损（带裂纹）钢结构，但过载疲劳损伤和湿热环境将造成加固结构界面粘结性能的退化，从而影响加固效果。本项目以CFRP加固的带圆孔钢板和受拉翼缘带缺口的工字钢梁为研究对象，采用理论分析、数值模拟和实验研究相结合的方法，对过载疲劳损伤和湿热环境共同作用下CFRP加固受损钢结构的耐久性开展研究。获得了桥梁过载疲劳谱及加速湿热老化的模拟试验方法，提出了钢桥结构损伤的智能检测技术，建立了CFRP加固钢结构粘接界面损伤和剥离的力学分析模型和数值模拟方法，揭示了过载疲劳损伤和湿热环境下界面粘结性能的退化规律，提出了过载疲劳损伤后CFRP加固钢结构在湿热环境作用下的寿命预测方法。本项目的研究成果为CFRP加固钢结构的设计规范提供了理论依据和实验数据，为钢桥和吊车梁等承受疲劳荷载构件的加固维修等工程应用奠定了良好的理论基础，并促进相关新材料、新技术和新构件的开发和应用。