FRP抗剪加固钢筋混凝土梁的尺寸效应研究

FRP has now been widely adopted for strengthening, retrofitting and updating infrastructures, with shear-strengthening being an important application. Size effect of RC members shear-strengthened with FRP is a significant issue to be addressed for the use of FRP in large practical members. The existing design methods of shear-strengthening FRP do not consider the size effect and may overestimate the shear contribution of FRP, leading to unsafe design. This project is proposed to investigate the size effect of RC beams shear-strengthened with FRP. In the first stage of this project, the bond-slip behavior of the FRP-to-concrete bonded interface with substrate concrete subjected to different stress states will be experimentally investigated by testing FRP-to-concrete bonded joint(referred to as joint hereafter); a meso-scale FE model exploiting the microplane model will then be developed for the joint to further explore the bond mechanisms of the FRP-to-concrete bonded interface. Based on the experimental and numerical results, a bond-slip model capable of accurately modeling the behavior of the interface with substrate concrete under different stress states will be proposed. The project is then focused on the study on the size effect of FRP shear-strengthened beams. In this stage, an FE model built upon a combination of microplane model and smeared crack model will be developed for FRP shear-strengthened beams based on the above bond-slip model. Beam tests will be carried out. The FE analyses in combination with the beam tests results will be deployed to investigate the effects of several factors (beam size, load condition, and anchorage) on the size effect, aiming to develop a rational and reliable design method for FRP shear-strengthened RC beams capable of considering the size effect. This project will lead to new knowledge in the field of FRP strengthening, and greatly promotes the use of FRP in civil engineering.

FRP已被广泛应用于基础设施的加固、维修和改造，抗剪加固是其中一个重要方面。FRP抗剪加固钢筋混凝土（RC）构件尺寸效应是FRP应用于实际工程时需要解决的一个重要问题，而现有FRP抗剪设计方法没有考虑上述尺寸效应的影响，对大尺寸构件将高估FRP抗剪贡献，导致不安全设计。为此本项目将研究FRP抗剪加固RC梁尺寸效应。本项目将首先利用搭接接头试验研究FRP基底混凝土应力条件对FRP与混凝土界面粘结性能影响，然后基于微平面模型建立精细有限元模型对FRP与混凝土搭接接头进行参数分析，结合试验结果，提出能考虑混凝土应力状态影响的FRP与混凝土界面粘结-滑移模型，进而发展结合微平面模型与弥散裂缝模型的新型有限元模型并进行参数分析，结合加固梁试验研究，探明一系列因素（梁尺寸、荷载、锚固条件）对梁尺寸效应的影响，从而建立考虑尺寸效应的外贴FRP抗剪加固设计方法。预期成果既有重要科学意义，又有广阔应用前景。

FRP抗剪加固钢筋混凝土构件尺寸效应是FRP应用于实际工程时亟待解决的一个重要问题，而现有FRP抗剪设计方法没有考虑上述尺寸效应的影响，对大尺寸构件将高估FRP抗剪贡献，导致不安全设计。本项目主要从如下四个方面系统地研究了FRP抗剪加固钢筋混凝土梁的尺寸效应。1）FRP与混凝土的界面粘结性能研究：利用专门设计的小梁试验研究了抗剪加固时FRP与混凝土的界面粘结性能，同时研究了锚固对FRP与混凝土界面粘结性能的影响，发表中文核心期刊论文2篇（其中1篇被EI收录），国际会议论文1篇，申请并获得中国发明专利1项，实用新型专利1项；2）FRP抗剪加固钢筋混凝土梁尺寸效应试验研究：重点研究了剪跨度比及梁高对抗剪加固尺寸效应的影响，发现FRP剥离破坏时，抗剪加固梁尺寸效应明显，而FRP拉断破坏时，FRP能有效抑制抗剪加固梁的抗剪强度尺寸效应，已发表国际会议论文1篇，中文会议论文1篇，另有2篇外文期刊论文在撰写中；3）带锚固装置大尺寸T型钢筋混凝土梁试验研究：研究了不同锚固装置对大尺寸T型钢筋混凝土梁抗剪加固效果的影响，相关研究成果在国际知名期刊《Composite Structures》发表论文1篇，在中文核心期刊《工业建筑》发表论文1篇， 申请并获得中国发明专利1项，实用新型专利1项；4）FRP抗剪加固钢筋混凝土梁理论分析：用解析解的形式求解了FRP断裂控制时的抗剪破坏全过程，并用有限元模型验证了解析解的正确，为进一步发展考虑FRP破坏过程及尺寸效应的抗剪强度模型奠定了基础，此项成果已经在国际顶级期刊《International Journal of Solids and Structures》发表SCI收录论文1篇，中文会议论文1篇；此外还推导了反弯矩区FRP抗剪加固混凝土梁FRP破坏全过程的理论解，已经发表国际会议论文1篇，还有1篇期刊论文正在撰写中；5）FRP加固钢筋混凝土梁剥离破坏有限元模拟：提出了可以模拟FRP剥离破坏（包含抗剪剥离）的准确有限元模拟方法，提出了动力学求解方法，验证了其有效性并解释了其合理性，相关成果已经发表SCI收录论文2篇（其中1篇发表在国际顶级期刊《Computers & Structures》），发表国际会议大会报告(Keynote lecture)论文1篇，受到国际知名学者的正面引用及好评。