长期荷载-环境耦合下RC间粘结性能的退化规律、劣化机理及时变模型研究

Reinforced concrete structures are inevitably suffered from the effect of load and environmental factors during the service life. The performance degradation of concrete and steel bar will be caused by coupling effect of load and environmental factors, and then the bond behavior between steel bar and concrete will be influenced. In this project, the change rules of bond behavior such as bond strength and bond slip creep between steel bar and concrete under the coupling effect of long-term load, dry-wet cycles and chlorine ion corrosion will be investigated based on experimental study and theoretical analysis. Quantitative analysis will be carried out to investigate the influence of every environmental factor on bond behavior. Meanwhile the corrosion products of steel bars, the development of microstructure and corrosive micro crack for concrete will be tested and analyzed. The relationship between the test results of microstructure of the interface material and the macroscopic mechanical properties will be established, and then the deterioration mechanism of bond behavior between steel bar and concrete will be studied. The time-dependant bond strength calculation model and time-dependant constitutive model of bond stress-slip between concrete and steel bar with different corrosion ratio, corrosion status based on elastic mechanics and damage mechanics will be given, respectively. This study is important to the improvement of the theory system of durability analysis for concrete structure. It could provide the experimental results and theoretical basis for computational theory of crack width and durability design of reinforced concrete structures in serviceability limit states under the coupling effect of long-term load and environmental factor.

钢筋混凝土结构在服役过程中，不可避免地承受着荷载、环境因素的共同作用，荷载与环境因素的耦合作用势必引起钢筋、混凝土性能的退化，进而对钢筋混凝土(RC)间的粘结性能产生影响。项目拟采用试验研究和理论分析相结合的方法，对长期荷载、干湿循环和氯离子侵蚀耦合作用下粘结滑移徐变、粘结强度等各粘结性能指标的变化规律进行研究，定量分析荷载和各环境因素对各粘结性能指标的影响规律；通过对界面处钢筋锈蚀产物及混凝土微观结构、锈胀微裂缝等的损伤演变进行测试、分析，建立界面微观结构测试结果与宏观力学性能间的逻辑关系，进而研究粘结性能在荷载与环境因素耦合作用下的劣化机理。最后，基于弹性力学+损伤力学建立考虑锈蚀率、锈蚀形态的钢筋混凝土间时变粘结强度计算模型及时变粘结滑移本构模型，本研究对于混凝土结构耐久性分析理论体系的完善具有重要作用，同时也可为正常使用极限状态裂缝宽度计算理论及耐久性设计提供试验和理论支撑。

钢筋混凝土结构在服役过程中不可避免的会受到长期荷载作用，对于沿海地区的钢筋混凝土结构还会遭受氯离子侵蚀，干湿循环作用。荷载与环境因素的耦合作用势必引起钢筋、混凝土性能的退化，进而对钢筋混凝土间的粘结性能产生影响。本项目主要针对长期荷载与环境因素耦合作用下钢筋混凝土粘结性能及其退化规律开展试验研究，包括持续荷载与氯离子侵蚀耦合作用、持续荷载与干湿损坏耦合作用、持续荷载与通电加速钢筋锈蚀工况下钢筋与混凝土的粘结性能退化规律及劣化机理。1）项目对长期荷载与环境因素耦合作用下的钢筋混凝土间粘结性能及其退化规律进行了研究，测试了长期荷载与不同环境因素耦合作用下钢筋混凝土之间相对滑移量随时间的变化关系和试件的粘结强度，探究了各因素对混凝土梁试件受力性能的影响机理。2）对长期荷载与环境因素耦合作用下粘结区段带初始裂缝的钢筋混凝土间粘结性能及其退化规律进行了研究，研究了裂缝对钢筋混凝土之间相对滑移量随时间变化的影响规律，建立滑移量-时间关系模型。3）研究不同时间长期荷载与环境因素耦合作用下钢筋在粘结区段不同部位的锈蚀规律和钢筋锈蚀随时间的发展规律，结合钢筋混凝土界面处微观结构测试结果阐明了粘结性能劣化机理。4）基于弹性力学理论，计算了钢筋非均匀锈蚀导致混凝土开裂的最大锈蚀深度，并根据混凝土开裂后锈蚀产物对裂缝的填充情况，建立了钢筋锈蚀程度与混凝土表面裂缝宽度之间的关系模型。5）建立考虑长期荷载和环境因素耦合作用下钢筋混凝土粘结强度-滑移本构关系模型。6）通过仿真计算的方式建立钢筋的通电锈蚀模型，对钢筋表面的锈蚀状态进行了模拟计算；提出了一种控制钢筋外表面锈蚀分布的预测方案，使加速锈蚀试验更真实的模拟自然条件下钢筋锈蚀。