嵌入自传感FRP筋和外包FRP组合加固RC柱的震后损伤控制和评估研究

After the steel rebar yielding, the damage develops easily for the RC column to cause large residual displacement. It will obviously decrease the post-earthquake structural resilience. Based on the existing research, the method is proposed in this proposal that the plastic hinge zone of the RC column is retrofitted with near-surface mounted self-sensing FRP bar and wrapped FRP sheet at the same time. The post-earthquake damage of the existing RC column is expected to be controlled and evaluated with the proposed method. In the method, the post-yielding bending stiffness of the RC column is increased by the near-surface mounted self-sensing FRP bar to control the damage, so as to decrease the residual displacement. Meanwhile, the residual displacement can be measured with the self-sensing capability of the self-sensing FRP bar based on the distributed optical fiber sensing technology. With the refinement of the wrapped FRP sheet, the deboning and buckling of the self-sensing FRP bar can be controlled and the concrete ductility can be also increased. Then, the study is arranged with three steps. Firstly, considering the character of the RC column under seismic loads, the sensing performance of the self-sensing FRP bar is improved as well as the bonding performance among the self-sensing FRP bar, glue and concrete. Secondly, the theoretical analysis modeling and design method are developed after comparing the factors influencing the post-yielding stiffness and residual displacement. Thirdly, multi-level damage evaluation method is proposed based on the measured residual strain distribution. The study results from this proposal will supply a new seismic retrofitting method for the RC column, which will increase the post-earthquake resilience of the transportation infrastructure, presenting both theory and actual application value.

RC柱在钢筋屈服后损伤易发展，形成较大的残余变形，严重影响其震后可恢复性。基于现有研究的进展与不足，本课题拟采用“嵌入自传感FRP筋与外包FRP组合加固塑性铰区”的方法控制和评估既有RC柱的震后损伤，思路为：嵌入自传感FRP筋提高RC柱的钢筋屈服后抗弯刚度，控制损伤，减小残余变形；基于分布式光纤传感技术，利用自传感FRP筋的应变传感特性测量残余变形，并评估结构损伤；外包FRP控制自传感FRP筋的剥离和屈曲，并适当提高混凝土的延性。为此，从三方面展开研究：针对嵌入式加固RC 柱的受力特点，改进自传感FRP筋的传感性能，并控制其与混凝土的粘结界面；考虑不同参数对提高屈服后抗弯刚度、控制残余变形的影响，建立理论分析模型和设计方法；利用残余应变分布，建立不同层次的结构损伤评价方法。课题研究成果将为RC柱的抗震加固提供新方法，增强交通设施的震后可恢复性，具有理论和实际应用的双重价值。

RC柱在钢筋屈服后损伤易发展，形成较大的残余变形，严重影响其震后可恢复性。基于现有研究的进展与不足，本项目采用了“嵌入自传感FRP筋与外包FRP组合加固塑性铰区”的方法控制和评估既有RC柱的震后损伤，具体为：嵌入自传感FRP筋提高RC柱的钢筋屈服后抗弯刚度，控制损伤，减小残余变形；基于分布式光纤传感技术，利用自传感FRP筋的应变传感特性测量残余变形，并评估结构损伤；外包FRP控制自传感FRP筋的剥离和屈曲，并适当提高混凝土的延性。为此，通过理论和试验等手段，从三方面展开了研究：. （1）自传感FRP筋及其性能：针对嵌入式加固RC 柱的受力特点，采用长标距传感的理念改进了自传感FRP筋，使其在混凝土多裂缝、大损伤、大变形下具有良好的分布式应变传感性能，同时试验研究表明其与混凝土的粘结界面可保证测试精度。. （2）结构关键参数评估方法：基于纤维模型理论，提出了自传感FRP筋和外包FRP组合加固RC柱的静态评估体系；基于模态理论，提出了动态评估体系；建立了裂缝位置识别、宽度评估的方法；基于材料力学中应变（或曲率）与结构挠度之间的关系，建立结构分布式动、静态位移的监测方法；提出了应变模态下的中和轴位置识别方法，并以此作为结构损伤的重要指标。. （3）自传感FRP筋和外包FRP组合加固RC柱的结构性能：通过试验研究，建立了自传感FRP筋和外包FRP组合加固RC柱的施工工艺及其关键参数，并获得了其基本力学性能，结构震后损伤和残余变形得到了有效控制。