预应力碳纤维（CFRP）板加固钢梁疲劳机理与寿命评估方法研究

Bonding prestressed CFRP plates to old steel beams is an innovative and perspective reinforcement technique, and the fatigue life accessment is a key issue. Numerical and experimental studies are conducted to investigate the fatigue mechanism and life prediction of steel beam strengthened with prestressed CFRP plates. Firstly static and fatigue behavior of anchors for prestressed CFRP plates are discussed to show the fatigue damage mechanism based on the previously developed anchor. Then a full-range analysis of the reinforced steel beam subjected to various loadings is presented to study the load-transfer mechanism and prestress control through verifications of respective static tests, and the numerical and experimental results provide the method to determine the reasonable permissible tensional pre-stress level of CFRP plates. Furthermore the important parameters, including levels of CFRP pre-stress and initial damages in steel beams, are studied to reveal the fatigue mechanism. Then fatigue tests are carried out based on the parametric study.In the end based on the fracture mechanism and fatigue tests, a holistic fatigue life assessment method is given according to fatigue damage accumulation model. This new prediction method focuses on the prestress levels of CFRP plate with considering the performance of anchors and initial damages in steel beams. The achievement will make a good reference to the design and code development of steel bridge repairing.

预应力CFRP板加固旧钢梁技术应用前景广阔，其疲劳寿命评估是关键技术。本课题拟通过仿真分析和疲劳试验，研究预应力CFRP板加固钢梁结构体系疲劳机理和寿命评估方法。首先基于前期研制的锚具，探讨预应力CFRP板锚固体系的主要受力模式及疲劳失效机理，揭示疲劳损伤机制；其次建立预应力CFRP板加固钢梁的受力全过程分析模型，研究不同受力模式下加固梁的传力机制和预应力控制方法，并进行静力试验，总结理论和试验研究成果，提出CFRP板最佳预应力水平的确定方法；再次通过关键影响因素，如预应力水平和梁初始损伤度等，与疲劳强度关系规律的研究揭示疲劳机理，并依据参数分析结果进行疲劳试验；最后基于断裂力学理论和疲劳试验成果，采用疲劳累积损伤律，建立预应力CFRP板加固钢梁疲劳累积损伤模型，并提出以预应力为中心、综合考虑锚具性能和钢梁初始受损程度的整体疲劳寿命评估方法。研究成果可为钢桥加固设计及规范制定提供重要参考。

预应力CFRP板加固旧钢梁技术应用前景广阔，其疲劳寿命评估是关键技术。本课题通过仿真分析和疲劳试验，研究预应力CFRP板加固钢梁结构体系疲劳机理和寿命评估方法。首先优化设计锚具，通过理论和试验研究预应力CFRP板锚固体系的主要受力模式及疲劳失效机理，结果表明：预紧压力和界面特性是关键因素，锚具承受疲劳应力幅70MPa作用时锚固效果仍良好；其次建立预应力CFRP板加固钢梁的疲劳机理分析模型，结果表明：裂纹扩展削弱了截面几何刚度，最终导致钢梁疲劳断裂；最后对不同有效预应力水平CFRP板加固的损伤钢梁进行疲劳试验，结果表明：CFRP板有效预应力水平1000MPa是最优的预应力控制水平，加固后疲劳寿命提高至少 3倍以上。研究成果可为钢桥加固设计及规范制定提供重要参考。