预应力束局部区域锈蚀及锈断后应力的传递和锚固性能

Insufficient grouting and seal anchor exist widely in the post-tensioned prestressed concrete (PC) bridges. This leads easily to local corrosion or fracture of prestressing tendons, adversely affecting the safety of bridge. Based on the above issues, this project will systematically investigate the transfer and anchorage behavior of post-tensioned prestressing tendon after local corrosion or fracture. The features in the project is that the study focus on the shear flow transfer mechanism between the whole bundle of tendon and grouting. Both the experimental tests and theory analysis will be adopted. The main tasks include: (1) The accumulation and development of corrosion rust affected by bellow constraint and insufficient grouting, the development mechanism of corrosion-induced expansive pressure, and the prediction model of expansive pressure and grouting cracking; (2) The degradation of bond performance, the development of the meshing cracks, the microscopic model of bond force transfer, and the bond-slip relationship of corroded tendon; (3) the transfer and anchorage behavior of post-tensioned prestressing tendon after local corrosion or fracture, the quantification of the coupling effect between Hall effect and corrosion-induced expansive, the force equilibrium and deformation coordination, and the computing model of the transfer and anchorage length of post-tensioned prestressing tendon after local corrosion or fracture. This work will help to determine the damaged region, understand the stress distribution on structures, and provide some calculation basis for the carrying capacity evaluation and the reinforcing design of PC bridge deteriorated by corrosion.

后张预应力混凝土桥梁存在压浆不实、封锚不严等病害，易引起预应力束局部区域锈蚀，甚至断裂，威胁桥梁安全。本项目以此为背景，针对预应力束局部区域锈蚀及锈断后应力的传递和锚固性能展开研究，其特色在于关注锈蚀预应力束整束与压浆界面间的剪力流传递问题。本项目拟采用试验和理论相结合的方法，主要研究内容包括：(1)研究波纹管约束和缺陷压浆影响下预应力束锈蚀产物的堆积过程，揭示锈胀力发展规律，建立孔道压浆界面锈胀损伤预测模型；(2)研究锈蚀/锈胀损伤对预应力束粘结性能的影响，揭示压浆齿合裂纹发展规律，构建粘结微观传力模型进行理论分析，提出锈蚀预应力束粘结滑移本构模型；(3)揭示锈蚀及锈断预应力束应力传递和锚固机理，量化霍尔效应与锈蚀膨胀耦合影响，提出锈蚀及锈断预应力束应力传递和锚固长度计算方法。研究成果可用于确定锈蚀损伤的影响范围，明确结构的应力分布状态，为该类桥梁承载力评定和加固设计提供依据。

后张预应力混凝土桥梁存在压浆不实、封锚不严等病害，易引起预应力束局部区域锈蚀，甚至断裂等病害。本项目以此为背景，在预应力混凝土结构锈胀、锈蚀预应力束粘结性能劣化、锈蚀断裂预应力传递和损伤结构加固方面开展了一些研究工作，具体内容和结论如下：(1)揭示了捻制预应力筋锈蚀和产物填充特征，明确了锈胀裂缝发展规律，建立了相应的表征和预测模型；基于红外和热重分析了预应力筋锈蚀产物膨胀特性，揭示了预应力水平、预应力管道、压浆质量、保护层厚度等对后张预应力筋锈胀开裂特征的影响；在此基础上，基于断裂力学和厚壁圆筒理论，提出了预应力混凝土结构锈胀力和胀缝预测模型。(2)设计6个足尺度预应力束试件进行预应力束局部断裂和拉拔试验，分析了断口附近预应力束应力发展规律，揭示了预应力束断后二次锚固规律及影响因素，探究了预应力束试件拉拔破坏特征和界面剪力传递机制，揭示了局部断裂预应力束粘结滑移机理；构建了预应力束整体滑移面及有效工作面确定原则，推导了预应力束粘结应力计算公式，提出预应力束与混凝土间粘结性能评价方法；提出了一种基于钢纤维磁吸增强力筋与混凝土粘结性能的方法，能有效改善断裂力筋的应力传递和锚固性能。(3)研发了一种基于光纤传感预应力传递和锚固长度监测装置及方法，具备精度高、耐久性好等优点；设计5片混凝土梁开展力筋局部断裂试验，揭示了局部断裂后的预应力筋再次锚固特征及对构件抗弯性能的影响；考虑预应力筋断裂霍尔回缩和锈蚀膨胀耦合效应，建立了断后预应力筋与混凝土接触径向压力计算模型，揭示了力筋与混凝土接触界面剪力传递规律，基于力筋与混凝土应变协调关系提出了断裂预应力筋应力传递长度计算方法。(4)针对预应力束局部锈蚀断裂等病害，研发了系列桥梁结构局部损伤加固提升方法，揭示了自密实混凝土加固既有结构界面粘结特征。这些成果对于完善预应力束局部锈蚀损伤混凝土桥梁承载力评定和加固设计理论具有科学意义和应用前景。