基于损伤累积效应的桥隧搭接结构地震动力响应研究

Damage occurs on bridge and tunnel overlapping structure in soft rock when earthquake of moderate intensity and above happening, and then the mechanical stiffness and strength of the structure decreased, thus directly led to changes on the dynamic characteristics of the structure. But how to evaluate the mechanical properties accurately of the bridge or the tunnel structure under the earthquake in one or several times becomes the key problem to structure dynamic response analysis when accumulative damage has been considered under the earthquake. The application research based on the seismic simulation shaking table tests of the bridge and tunnel lap joint structure in soft rock and indoor material tests, with the help of damage mechanics and dynamics method, will study the complex physical and geometrical nonlinear response of the bridge and tunnel overlapping structure under earthquake, damage the disaster behavior and the theoretical description, reveal the generating mechanism and evolution law of cumulative damage on bridge, tunnel and its surrounding rock, evaluate the influence to the seismic damage of the bridge and tunnel lap joint structure under different ground motion parameters, reveal the seismic damage mechanism of a catastrophic failure, propose the bridge and tunnel joint structure seismic damage failure and dynamic disaster criterion, and propose the seismic performance evaluation index and method based on the design method of performance theory on the bridge and tunnel lap joint structure in soft rock.

软弱围岩条件下的桥隧搭接结构在中等强度以上地震作用下将产生损伤，结构的刚度和强度等力学性能随之降低，从而直接导致结构动力特性的变化。而如何准确地评价桥隧搭接结构在一次或多次地震作用后的力学性能，则是在充分考虑损伤累积效应后进行结构地震动力响应分析的关键。本申请课题拟在软弱围岩桥隧搭接结构的地震模拟振动台试验及室内材料性能测试的基础上，借助损伤力学和动力学的方法，研究地震作用下桥隧搭接结构的复杂物理和几何非线性的动力响应、损伤灾变行为与理论描述，揭示桥隧搭接结构及围岩土体在地震作用下的结构累积损伤的产生机理及其演化规律，评估不同地震动参数对桥隧搭接结构地震损伤的影响，揭示其地震动力损伤灾变破坏机理，建立桥隧搭接结构的地震损伤及动力灾变失效破坏准则，并提出基于性能设计理论的软弱围岩桥隧搭接结构的抗震性能评价指标与方法。

目前国内外对软弱围岩条件下的桥隧搭接结构在多次地震作用下的损伤评估和地震响应的研究工作开展得很少，相关工程抗震设计和震害评估工作还缺乏试验参考和理论支撑。本课题综合利用大型振动台试验、室内材料性能试验、数值模拟和理论分析等多种研究方法，研究了不同地震作用下桥隧搭接结构的地震动力响应与灾变行为。研究结果显示，在强烈地震作用下，桥隧搭接结构多处薄弱和敏感结构部位将会产生显著累积损伤效应与复杂动力响应，不利结构安全与稳定。地震动参数尤其地震波加载方向、激振强度和能量分布类型等的改变，对其损伤累积、动力响应及灾变行为的影响比较显著。通过研究，建立了桥隧搭接结构地震损伤判别标准与动力灾变失效破坏准则。同时，揭示了高速铁路分离式桥隧搭接结构及软弱围岩高速公路桥隧搭接段在地震作用下的损伤演化过程、动力特性和动力响应变化规律及动力灾变破坏机理，提出了适用于软弱围岩条件下桥隧搭接结构抗震性能评价的实用方法与抗震设防措施。本研究为探讨复杂条件下桥隧搭接结构的地震响应规律及其诱发机制奠定了坚实的工作基础，同时为桥隧搭接结构优化设计及防震减灾等提供了重要科学依据与启示性线索。