基于频率变化率的结构刚度非均匀退化识别

针对不利环境作用、损伤等易造成结构局部损伤且刚度退化程度不均匀的问题,以受弯梁为研究对象,从构件动力特性入手,综合考虑损伤前后的模态挠度曲率和固有频率变化,提出了基于频率变化率的刚度非均匀退化识别方法。首先,在柔度矩阵的基础上推导模态挠度曲率,通过损伤前后模态挠度曲率的改变量识别损伤位置参数,判定损伤区域;其次,对损伤区域进行节段划分,从欧拉-伯努利梁的动力方程出发建立损伤程度、损伤区域位置参数与固有频率之间的矩阵函数,实现直接利用频率值变化评估构件不同区域损伤程度。研究结果表明,该方法能很好地识别结构局部损伤位置和损伤程度,尤其是对于结构局部刚度不均匀退化的评估具有明显的优势。

Identification of Non-uniform Stiffness Degradation in Structure Based on the Change Rate of Frequency

To study on non-uniform stiffness degradation in structure caused by adverse environmental effects and damage, an identification method for stiffness degradation is proposed based on the change rate of frequency using bending beam model, which considers the variation of modal deflection curvature and natural frequency before and after damage. Firstly, modal deflection curvature is derived through a flexibility matrix, and the damage area and location are determined through the variation of modal deflection curvature before and after damage. Then, the damage area is divided into segments, after that the matrix function of damage extent, location parameters of damage area and natural frequency is established according to the vibration theory of Euler-Bernoulli beam. It can directly assess the damage degree of different segments through the change rate of frequency. The results show that the method can precisely identify the location and extent of the local damage, and has advantages in assessment of the non-uniform stiffness degradation in structure.