结构局部损伤诊断的应变模态方法——分析与应用

Strain mode method for diagnosis of local damage of structure: analysis and application

监测和诊断大型工程结构的健康状况,评估其安全性已成为未来工程的必然要求。基于利用局部反应监测结构局部性能的设想,利用应变模态的局部性特点进行结构的局部损伤诊断。首先由传递函数对应变模态进行贝叶斯区间估计,通过一混凝土框架模型的模态试验,分析应变模态测试的不确定性;然后对混凝土框架柱进行局部加强,考察应变模态界定损伤的能力。结果显示,固有频率的不确定性程度最小,应变模态振型与位移模态振型相比,各测点的变异程度差异较大,而阻尼比受不同类型测试系统影响较大;在高阶应变模态对结构局部损伤发生误判的情况下,一阶应变模态可以界定损伤,准确指示损伤部位。

Based on the structural frequency response functions, the uncertainty of strain modal parameters are analyzed by Bayesian method. The modal tests of a structural model with four-story reinforced concrete frame are conducted in laboratory. And the ability of identifying the stiffness change of the concrete column using strain mode is tested. It is shown that the uncertainty degree of the natural frequency is very small. Comparing with the displacement mode shape, the variations of strain mode shapes at different measuring points were quite different. The damping ratio is more affected by the type of the test system. In spite of the case of misjudging local damage with the high order strain mode, the first order strain mode can judge and exactly indicate the location of the damage.