基于设计薄弱环节理念的混凝土结构抗震设计方法研究

One of the key factors in ensuring the seismic performance of Reinforced Concrete structures under rare earthquakes is to realize desirable failure mechanism. But the inertial strategy via enhancing structural resistance is not the unique way. Instead, the seismic design concept based on designing weak links is more suitable to the main strategy of seismic fortification. The research related to this still remains at the concept and case level. It requires more activities to develop a seismic design method based this concept. In this project, internal force redistribution rule by means of the method of combining theoretical analysis, nonlinear simulation and experimental validation; then the validity of controlling the failure mechanism under strong earthquakes in Chinese seismic design code is checked and estimated. Moreover, the project will propose a multi-index standard for evaluating a rational failure mechanism. By means of comparison of seismic performances of typical structures with possible failure mechanisms, feasible failure mechanism is proposed. With this respect, a seismic design method based on designing weak links is provided, and then its validity is investigated by means of numerical analyses and model tests. The research achievements of this project render a novel strategy for structural seismic design, which is a beneficial supplement to existing seismic design methods. And the achievements of this project can be applied to seismic design of structures under strong earthquake, which exhibits great scientific significance and application value.

强震中实现预期的合理破坏模式是保证混凝土结构大震抗震性能的决定性因素之一。抗震规范修订所沿袭的"加强-加强-再加强"的惯性思路不是实现合理破坏模式的唯一出路，基于设计薄弱环节的抗震设计理念更符合抗震设防的总体策略，但尚停留在概念和个案层面，发展到具体的抗震设计方法还有很多工作要做。本项目通过理论分析、非线性数值模拟和试验研究相结合的方法，研究典型RC 结构强震内力重分布规律；对我国现行抗震规范设计方法控制强震下出现预期破坏模式的有效性进行校验和评估；建立基于多指标的合理破坏模式评价标准和方法，进行典型结构可能的破坏模式的评价并给出设计用推荐方案集；建立基于设计薄弱部位的抗震设计方法体系和统一设计步骤，通过数值分析和模型试验考察其有效性。项目研究成果为结构抗震设计提供一种新的思路和方法，是对现有抗震设计方法的有益补充，可广泛应用于结构强震阶段抗震设计，具有重要的科学意义和应用价值

合理有效地控制结构大震下的损伤机制和结构损伤的合理性评价是基于设计薄弱环节理念的混凝土结构抗震设计方法研究中亟需解决的重要问题。为合理评价结构构件损伤，根据低周疲劳理论和Miner准则，提出了合理考虑累积损伤效应的改进Park-Ang损伤模型，并提出了基于试验的钢筋混凝土构件概率损伤模型的标定方法以及样本扩容流程，为基于构件的易损性函数选取提供了建议；根据可靠度理论中的割集方法，对我国现行抗震规范设计的典型结构进行损伤机制校验和概率评估，识别出结构可能发生的主要典型损伤机制；以等代结构法为基础，提出了基于预设损伤的RC框架结构抗震设计流程，并通过算例分析验证了该方法在控制结构损伤（损伤机制、损伤程度、损伤分布）方面的有效性；在简化基于全概率的PEER-PBEE评价方法的基础上，综合考虑安全性和经济性，系统提出了结构破坏模式多指标评价方法，解决了结构破坏模式合理性评价指标单一的问题，评价方法为指导结构破坏模式选择和控制提供依据；由此从构件层次损伤到结构体系损伤机制，结合破坏模式多指标评价方法和预设损伤抗震设计方法，发展并建立基于设计薄弱环节理念的混凝土结构大震抗震设计方法；分别按现行规范和大震设计方法设计了两榀四层三跨的RC框架结构并进行低周反复加载试验，验证了大震设计方法的有效性。