曲线梁桥地震落梁失效多级控制系统的理论与试验研究

The bridge unseating failure will lead to transportation interruptions, and it is one of the most serious and ubiquity bridge damages during earthquake. At present, qualitative construction measures based on earthquake disasters and experiences are mainly adopted to control the unseating failure of bridges during earthquake. However, the current countermeasures can not effectively provide unseating failure prevention and structural safety protection for curved girder bridges with bending-torsion coupling vibration characteristic during earthquake. Based on the research achievements of multi-level control mode for unseating failure prevention of concrete girder bridges, a new multi-level control system for unseating failure prevention of curved girder bridges subject to earthquake is developed according to the conceptions of passive energy dissipation, multi-failure and damage reduction in this project. The control system provides respectively two different control performances including energy dissipation-based displacement restriction and unseating prevention, and the two level control performances can be automatically transformed according to the preset threshold value of structural damage reduction fuse. Firstly, the two-level control system of unseating failure prevention is developed for curved girder bridges based on the research achievements. Secondly, the control characteristics, energy dissipation-based displacement restriction properties and unseating prevention ability are respectively studied by theoretical analysis and numerical simulation. The control system response behavior and bearing failure influence in different control states and transformation state are revealed. In addition, the reliability and effectiveness of two-level control performance and control transformation function, and the correctness of theoretical analysis results of unseating failure multi-level control system are verified by experimental research. Finally, the optimum performance control strategy and parameters are determined by control theory.

落梁失效将导致交通运输系统的中断，它是最为严重和普遍的桥梁震害之一。目前采取的地震落梁失效控制措施主要基于震害经验的定性构造措施，无法满足具有弯扭耦合地震响应特性的曲线梁桥落梁控制与安全保护的需求。本项目拟在课题组前期关于混凝土梁桥多级失效控制模式研究的基础上，基于耗能减震、多级设防和结构分灾思想，发展一种具有耗能限位和防止落梁两级控制性能并能通过预设分灾保险阈值实现两级控制自动转换的新型落梁失效多级控制系统。首先，发展课题组前期建立的可实现两级控制性能的桥梁地震失效控制系统，使其适应于曲线梁桥落梁控制要求。其次，通过理论分析和数值模拟研究该系统的控制性能、耗能限位特性和防落梁能力，认识不同控制阶段和控制转换状态下系统响应行为及支座破坏影响等。再次，通过试验检验系统实现两级控制功能和转换控制功能的可靠性和有效性，以及理论分析结果的正确性。最后，以控制理论确定该系统的最优控制策略及优化参数。

落梁失效将导致交通系统的中断，它是最为严重和普遍的桥梁震害之一。目前采取的地震落梁失效控制措施主要是基于震害经验的定性构造措施，无法满足具有复杂地震响应特性的曲线梁桥落梁控制与安全保护的需求。本研究对混凝土曲线梁桥的非线性地震反应及落梁倒塌进行了全过程、多尺度、精细化数值模拟，揭示了曲线梁桥的落梁机理。基于耗能减震、多级设防和结构分灾思想，提出了一种具有耗能限位和上部体系连续化两级控制性能并能通过预设分灾保险阈值实现两级控制自动转换的新型落梁失效多级控制系统。建立了多级控制系统的力学模型，研究了控制系统的工作机理和转化模式，评估了控制系统对桥梁地震反应和落梁失效的控制效果，揭示了两级控制功能转换时结构的内力重分布规律。分析了不同结构参数和控制参数下桥梁的地震反应和控制效果，考察了控制系统的参数影响规律。建立了多级控制系统的性能优化原则，确定了分灾保险丝阀值的合理化取值。通过试验检验了系统实现多级控制功能和转换控制功能的可靠性和有效性。研究结果表明，全过程、多尺度、精细化的数值模拟是真实再现复杂工程结构地震损伤、破坏及倒塌等灾变的有效途径。地震动特性、主梁移位、邻联动力特性差异、盖梁与横系梁的设置、支座布置、弯扭耦合效应及碰撞效应是导致落梁倒塌的主要因素。落梁失效多级控制系统实现了墩-梁连接控制模式和梁-梁连接控制模式的优势互补，可以在不过度增加桥墩地震作用的情况下有效地减小墩-梁相对位移，实现了对主梁地震落梁的有效控制和对桥墩的安全保护。控制系统的效果依赖于各种控制参数，包括墩-梁连接刚度、墩-梁连接强度阀值、梁-梁连接刚度、梁-梁连接初始间隙及结构邻跨刚度比，控制参数的设计需要同时考虑墩-梁相对位移控制效应和桥墩内力控制效应两者的影响，采用优化方法确定。本项目的研究结果可以为桥梁抗震性能提升提供理论基础和技术支撑，也为结构灾变失效多级控制技术的研究提供理论借鉴和有益参考。