钢筋混凝土框架节点弯折钢筋抗震锚固性能的试验与理论研究

Bond-slip mechanism between reinforcing bar and concrete is an important issue in the design theory of concrete structures. Although the issue has been considered for about 100 years and the macroscopic phenomena of the bond-slip behavior have been recognized by engineers, current design codes still specify empirical equations for the development length of reinforcing bars, and the anchorage failure of reinforcing bars in beam-column joints frequently occurs under earthquake action. As a result, an in-depth study of the development length design has been required from engineering groups. In this research project, addressing the engineering practice in China, the seismic anchorage performance of 90-degree hooked bars in exterior joints of RC frame structures is studied: the experimental research, theoretical analysis, numerical simulation, and statistical analysis methods are used. The goal of this research project is 1) The interaction mechanism between 90-degree hooked bar and concrete under complex stress conditions is explained clearly; 2) An anchorage mechanism model for 90-degree hooked bar is developed; 3) Critical parameters for the interaction model between reinforcing bar and concrete is investigated using test data; and 4) A new anchorage design method satisfying various design requirements is developed on the basis of probabilistic analysis. Thus, the research focuses on the key scientific issues such as anchorage mechanical model of 90-degree hooked bar and probabilistic analysis of anchorage failure. The scientific significance of this research project is secured by carefully designed comparative tests, in-depth acquisition of test data, and theoretical analysis combined with finite element numerical simulation.

钢筋与混凝土之间的粘结滑移机理是混凝土结构设计理论中的一个重要问题，虽然已有近百年的研究历史，其受力行为的宏观现象已被工程师所认识，但偏于经验的钢筋锚固设计方法在理论上并不完善，地震作用下钢筋混凝土框架节点的锚固破坏时有发生，因此有深入研究钢筋锚固设计理论的工程需求。项目结合我国工程实践，以90°弯折锚固的钢筋（简称为弯折钢筋）在框架边节点中的抗震锚固性能为主要研究内容，采用试验研究、理论分析、数值模拟和统计分析的方法，解释复杂应力状态下钢筋和混凝土的相互作用机理，建立弯折钢筋锚固机理模型，基于试验数据反演钢筋与混凝土相互作用本构模型参数，在概率分析的基础上提出满足不同需求的钢筋锚固设计方法。项目研究围绕弯折钢筋锚固机理力学模型和锚固破坏概率分析等科学问题展开，精心设计对比试验，深度采集试验数据，理论分析与有限元数值模拟相结合，有非常明确的科学意义。

为进一步认识钢筋与混凝土的锚固机理，不断完善我国相关规范的设计方法，项目围绕不同锚固环境下各种钢筋形式（直钢筋、弯折钢筋，带锚固板钢筋、并筋、搭接钢筋）的锚固性能试验以及梁的抗剪试验等积累了量大面广的试验数据。在理论分析层面，针对弯折钢筋锚固机理、深梁受剪机理等问题进行了深入的研究，得到的主要结果如下：.（1）研究了不同锚固环境下的弯折钢筋锚固性能的影响因素、受力特性，进一步明确了弯折钢筋锚固破坏临界控制条件，提出弯折钢筋锚固机理模型。.（2）基于弯折钢筋锚固试验数据库和理论分析模型, 确定揭示其锚固破坏的概率特征，提出满足不同需求的弯折钢筋锚固的三水平设计方法，可应用于现浇混凝土结构和装配式混凝土结构中，解决不同场合的设计需求。.（3）研究了不同钢筋形式(直钢筋、带锚固板钢筋、并筋、搭接钢筋)的锚固性能的影响因素、受力特性，并提出了相应的锚固锚固承载力经验公式，解决了不同应用场景的设计需求。.（4）研究了钢筋混凝土深梁抗剪、连梁抗剪等复杂应力结构的影响因素、受力特性，进一步明确了其失效机理，并在此基础上提出相应的力学模型。.本项目的研究成果丰硕，具有创新性，主要用于修订混凝土结构设计规范，提高混凝土结构设计水平。