基于自然激励技术和FT时移特性的模态阻尼比识别方法

Approach for identifying modal damping ratios based on natural excitation technique and time-shifting property of FT

基于环境激励下结构动力响应信号分析与处理识别结构的模态参数,是结构健康监测和损伤诊断的一个重要环节,目前为止,要得到较为可靠的识别结果仍有一定困难,尤其是模态阻尼比。基于自然激励技术和傅里叶变换的时移特性,提出了一种新的结构模态阻尼比估算方法,通过理论推导和仿真算例验证了该方法的可行性,进而利用一刚构-连续组合梁桥在环境激励下的动力测试数据,通过该方法对其阻尼比进行了识别,并将识别结果与数据驱动随机子空间法的识别结果进行了对比。结果表明:提出的方法可以减轻噪声影响,得到可接受的识别结果,可为大型工程结构阻尼比的识别提供一个方便和有效的途径。

Identification of structural modal parameters via processing the dynamic response signals under ambient excitation is an important procedure for structural health monitoring and damage diagnosis.Up to now,it is still difficult to obtain very reliable identification results,especially for modal damping ratios.Therefore,a new approach was proposed for identifying structural modal damping ratios based on Natural Excitation Technique(NExT)and time-shifting property of Fourier Transform(FT)in this paper.First,the feasibility of this approach is verified by theoretical derivation and numerical simulation.Then,the modal damping ratios of a rigid frame-continuous girders bridge were identified based on the dynamic test results under ambient excitation by the proposed approach and data-driven stochastic subspace identification(SSI-DATA),respectively.Comparison of the identification results indicates that the proposed approach is capable to alleviate the noise effect and obtain the favorable results.It can provide a convenient and efficient way to identify the damping ratios of large-scale engineering structures.