基于塑性铰外移的CFRP板条嵌入式加固RC框架节点抗震设计方法研究

Many already existing reinforced concrete (RC) beam-column joints designed according to earlier codes have deficient reinforcement details, such as without transverse reinforcement, and thus don't meet the principle of strong-joint weak-member. There are currently many strengthening methods for beam-column joints, including FRP application; after upgrading, however, beam plastic hinges often occur at the column face, which would induce bond failure of beam bars within the joint core, and further lead to the joint shear strength deterioration. The near-surface mounted (NSM) CFRP strips method has a number of advantages, such as fast and easy application, high strength/weight ratio and corrosion resistance, and favorable bond behavior. Using this method, several interior beam-column joints without transverse reinforcement from exterior frames will be strengthened to relocate the beam plastic hinge away from the column face in this project. The primary variables related to strengthening using NSM CFRP strips, the distribution and development of CFRP strip strain, and the shear behavior of upgraded joints will be studied in detail through theoretical approaches, tests and computer simulation. A seismic design method will be further proposed for rehabilitating beam-column joints with NSM CFRP strips based on the concept of plastic hinge relocation, which aims to provide a theory background for its wide application.

按早期规范设计的钢筋混凝土（RC）框架节点存在箍筋配置不足或锚固不良等典型缺陷，有悖于"强节点弱构件"的抗震概念设计原则。目前，包括粘贴纤维复合材（FRP）在内的节点加固方法较多，但仍存在一些不足 ，如无法避免梁铰形成于柱面，容易引起梁筋在核心区内的锚固粘结破坏，从而导致节点抗剪强度发生退化。CFRP板条嵌入式（NSM）加固方法具有高效高强、耐久性及粘结性能好等诸多优点。本课题拟结合此方法，基于塑性铰外移的设计理念，对核心区未配箍筋的RC边框架中节点进行抗震加固研究。以理论分析为主、试验验证为辅及数值模拟补充的研究思路，对CFRP板条嵌入式加固节点的主要设计参数、板条的应变分布与发展规律及加固节点的核心区抗剪强度的计算等方面展开系统而深入的研究。此基础上，提出基于塑性铰外移的CFRP板条嵌入式加固RC节点的抗震设计方法，为其工程应用提供理论依据。

部分现存RC框架节点存在箍筋不足等典型缺陷，在地震作用下易发生剪切破坏导致结构破坏甚而坍塌。既有的节点加固方法仍存在诸多不足，而CFRP板条嵌入式（NSM）加固方法具有高效高强、耐久性及粘结性能好等诸多优点。本课题结合此加固方法，基于塑性铰外移的设计理念，以理论分析为主、试验验证为辅及数值模拟补充的研究思路，对核心区未配箍筋的RC边框架中节点进行了抗震加固研究。本课题主要完成了6个NSM CFRP板条加固RC节点抗震性能试验研究，证明了加固方法可有效转移梁铰；通过参数数值分析及优化，确定了节点加固设计的主要影响因素及取值；基于混凝土双向拉压强度准则，提出一个NSM CFRP板条加固RC节点的抗剪强度计算模型，可用于节点抗剪设计。在此基础上，提出了基于塑性铰外移的CFRP板条嵌入式加固RC节点的抗震设计方法，为其工程应用提供理论依据。. 同时，本课题基于混凝土双向拉压强度准则，针对典型结构D区（包括普通及再生RC框架节点、预应力混凝土节点、FRP加固RC节点及深梁等）开展了系统的抗剪强度分析，建立了相应的改进软化拉压杆模型，并提出了精确而简便实用的抗剪设计公式，对结构D区的抗剪统一设计方法的建立打下了基础。