CFRP板加固损伤钢结构疲劳裂纹扩展与界面剥离耦合机理及寿命预测

The externally-bonded carbon fiber reinforced polymer (CFRP) plate technique can significantly improve the fatigue behavior of damaged steel structure and hence it has good application prospects. However, the issue on the interfacial debonding has not been addressed when using the CFRP plate for strengthening damaged steel structure. The project focuses on the interfacial debonding (hereafter referred to as the intermediate debonding) induced by the fatigue crack growth of damaged steel structure, with conducting series of experimental, theoretical and numerical studies. Firstly, fatigue tests of single-shear bonded joints will be conducted to study the fatigue behavior of the CFRP plate-to-steel interface. The degradation of the bond behavior and the debonding mechanism of the CFRP plate-to-steel interface will be investigated and the bond-slip model of the interface under fatigue loading will be proposed based on the test results. Secondly, the project will conduct fatigue tests of CFRP plate strengthened cracked steel plates and steel beams, to study on the interaction between the interfacial intermediate debonding and the fatigue crack growth in damaged steel structure and reveal the coupled mechanism between them. Thirdly, based on the study results above-mentioned, the prediction method of the intermediate debonding with the fatigue crack growth will be developed through theoretical analysis and numerical simulation. Finally, the project will establish the prediction method of the fatigue life of CFRP plate strengthened damaged steel structure, which will take the detrimental effect of intermediate debonding on the fatigue life into consideration. The study results of this project will make the prediction of the fatigue life of CFRP plate strengthened damaged steel structure more scientific and reasonable, which have an important theoretical significance and application value of engineering.

外贴碳纤维增强复合材料（CFRP）板技术可以显著提升损伤钢结构的疲劳性能，是一种具有良好应用前景的新型钢结构疲劳加固技术，但界面剥离问题暂未得到很好的解决。项目针对CFRP板加固损伤钢结构疲劳裂纹扩展引起的界面剥离（本项目称为中部剥离）问题，通过试验研究、理论分析和数值模拟等方法进行系统研究。首先，通过CFRP板-钢单剪节点疲劳试验，研究疲劳荷载下CFRP板-钢界面的粘结性能退化规律，揭示界面的剥离机理，建立界面的粘结-滑移退化模型；其次，通过CFRP板加固含裂纹钢板和钢梁疲劳试验，研究疲劳裂纹扩展与界面中部剥离的相互影响规律，揭示两者的耦合机理；进一步，通过理论分析和数值模拟，建立界面中部剥离预测方法；最后，建立考虑界面中部剥离影响的CFRP板加固损伤钢结构疲劳寿命预测方法。项目研究成果可以使CFRP板加固损伤钢结构疲劳性能预测更加科学合理，具有重要的理论意义和工程应用价值。

应用外贴碳纤维增强复合材料（CFRP）板技术提高钢结构的疲劳寿命是一种新型钢结构疲劳加固技术，项目针对CFRP板疲劳加固损伤钢结构的界面中部剥离和疲劳寿命预测问题，研究了静力和疲劳荷载下CFRP板-钢界面的粘结性能、CFRP板加固损伤钢构件的疲劳性能、界面的中部剥离预测方法以及考虑中部剥离的疲劳寿命预测方法。首先，应用数字图像相关（DIC）方法对静力和疲劳荷载下CFRP板-钢界面的粘结性能进行了研究，发现结构胶类型和胶层厚度对界面承载力有明显影响；随着荷载比的增加，界面疲劳寿命急剧下降，疲劳寿命的对数与荷载比呈线性关系，在相同的荷载幅下，采用具有较大界面极限承载力的结构胶、增加胶层厚度均可以提高界面的疲劳寿命；发现针对不同的结构胶，界面粘结-滑移关系呈双线性或三折线，通过理论分析建立了界面的粘结-滑移理论模型。其次，开展了CFRP加固含裂纹钢板和损伤钢梁的疲劳试验，发现外贴CFRP可以显著降低钢构件的裂纹扩展速率，提高疲劳寿命，而结构胶力学性能对界面的中部剥离有重大影响。然后，采用ANSYS有限元软件，建立了非线性有限元模型，将界面粘结-滑移参数输入到非线性弹簧单元中，得到了界面的中部剥离预测方法。最后，建立了CFRP板加固钢结构应力强度因子计算方法，通过删除剥离区域的线性弹簧单元考虑界面中部剥离对疲劳性能的影响；结合线弹性断裂力学理论，建立了CFRP板加固含裂纹钢板和钢梁的疲劳寿命预测方法，实现了CFRP加固钢梁主、次裂纹以及腹板裂纹的同步模拟；采用建立的预测方法，系统分析了10个因素对疲劳裂纹扩展的影响；通过理论分析和有限元模拟，建立了CFRP板加固含中心裂纹钢板、含单边裂纹钢板和下翼缘开裂钢梁的应力强度因子理论计算公式。项目研究成果促进CFRP板加固损伤钢结构疲劳性能预测更加科学合理，具有重要的理论意义和工程应用价值。