高速铁路模型箱梁静力非线性和动力损伤关系研究

桥梁结构在荷载作用下的静力非线性与结构动力特性之间的关系是结构损伤识别领域的重要问题。基于高速铁路模型箱梁的重复荷载试验，采用平面非线性有限元分析方法对静力非线性和动力损伤之间的关系进行了研究。通过定义混凝土等效应力－等效塑性应变曲线来定义其弹塑性行为。对数值模型加载到各级荷载后卸载进行动力特性分析，即卸载后计算自振频率和振型。计算结果表明：采用平面非线性有限元分析方法可以比较准确地对箱梁模型进行非线性分析，除了初始模型刚度存在一定误差外，结构的骨架曲线的特征值、加卸载刚度和残余位移吻合较好。在进行非线性分析后进行动力特性是分析可行。竖向频率值的变化能够反映静力非线性发生后结构的损伤出现和损伤的发展规律，这为结构动力损伤识别提供了有效的途径。

Research on the relationship of the dynamic characteristics and static performance of high-speed railway box girder model under repeated loading

The relationship between nonlinear response under static loads of bridge structures and dynamic characteristics is important issue in the areas of structural damage identification. Based on model test of high-speed railway girder under repeated loading, the relationship between nonlinear and dynamic characteristic using planar nonlinear finite element method has been studied. The elastic-plastic behavior of concrete is defined by the equivalent stress and equivalent plastic strain. After the numerical model is unloaded from different load levels, the mode analysis is performed, that is the vibration frequency and mode shape is calculated after unloading. The results show that the non-linear characteristic of box girder can be modeled accurately using the planar nonlinear finite element analysis method. The characteristic values of skeleton curve, loading and unloading stiffness and the residual displacement from finite element method are in good agreement with that from experiment, except model error in the initial stiffness. The modal analysis based on static nonlinear analysis is practicable. The value changes of vertical frequency can reflect the occurrence of static nonlinear structural damage and the law of damage development. That is an effective way to damage identification from dynamic characteristics of structural.