无粘结预应力FRP板增强RC框架抗倒塌性能及设计方法研究

在极端荷载作用下，当钢筋混凝土(RC)框架关键构件(如柱)失效并引起结构发生大变形时，结构需要通过周边框架梁形成悬链线效应来实现内力重分布，从而避免结构发生倒塌。对于早期未进行抗倒塌设计的RC框架，节点处梁纵筋不连续和锚固不可靠等问题会影响悬链线效应的发挥。申请人前期研究提出采用无粘结纤维增强复合(FRP)板作为悬链机构增强RC框架的抗倒塌加固方法，初步验证了该方法的有效性。本项目基于前期研究工作，拟采用试验、有限元和理论分析等方法对无粘结预应力FRP板增强RC框架抗倒塌性能进行更深入的研究，并重点考察FRP板预应力对加固效果的影响。主要内容包括：1)揭示FRP板与RC框架子结构抗倒塌协同工作机理；2)研究FRP板增强RC框架整体结构的倒塌破坏机理；3)建立FRP板增强RC框架抗倒塌承载力的计算模型，并提出基于性能的抗倒塌设计方法。本项目成果可为RC框架结构抗倒塌的加固设计提供参考。

Reinforced concrete (RC) frames can be subjected to the accidental extreme loads. In case of the occurrence of failure of the load-carrying columns, their adjacent beams need to activate the catenary action to sustain the large deformation and to achieve the redistribution of internal forces, thus eventually preventing progressive collapse. For the existing RC frames previously designed without consideration of progressive collapse, there are certain problems, such as discontinuous reinforcement and unreliable anchorage at the joint, which brings about the difficulty for the effective development of catenary action of beams. .In previous work, a method using unbonded fiber reinforced polymer (FRP) plates severing as catenary to retrofit RC frames was therefore proposed to mitigate collapse. The effectiveness of this method was tentatively verified through collapse tests. Based on this work, this project tries to further investigate the collapse performance of RC frames retrofitted with unbonded prestressed FRP plates by using collapse test, finite element modelling, theoretical analysis, and other methods. The prestressing level of unbonded FRP plates is taken into significant consideration. The specific content is as follows: 1) revealing the cooperative working mechanism between FRP plates and RC frame substructures to resist collapse; 2) investigating the failure mechanism of the whole RC frames retrofitted with unbonded prestressed FRP plates; 3) establishing the calculation model of collapse resistance of RC frames retrofitted with unbonded prestressed FRP plates and proposing the performance-based design method for preventing collapse. The research results would have a reference value for the strengthening design of RC frames to mitigate collapse and be of great significance in the theory study and engineering application.