应用HHT方法识别刚度突降线性SDOF体系的动力特性

以线性单自由度(SDOF)体系的刚度突降来模拟损伤引起的结构力学性能的变化,利用HHT方法分析了这种体系的强迫动力响应,并将体系动力响应的Hilbert谱与Morlet小波谱所蕴含的物理意义及分辨率特性进行了比较．分析结果表明：在规则的简谐波输入下,结构动力响应的Hilbert谱能够分辨出体系的稳态与瞬态反应,利用瞬态反应,能够识别损伤引起的体系自身动力特性的变化；在不规则的地震动输入下,由于输入的复杂性,Hilbert谱不能够将体系的稳态与瞬态反应分解开来,但是利用体系动力响应Hilbert谱的瞬态能量分布特征定义了一种瞬时卓越频率时程(PIF),其随时间的变化能够在一定程度上描述损伤引起的体系动力特性的变化．

Applying HHT to Identifying the Dynamic Properties of Linear SDOF System with Sudden Drop of Rigidity at Some Instant

The damage-induced change of structural mechanical properties is simulated by sudden drop of rigid- ity of linear single-degree-of-freedom(SDOF)system whose forced dynamic responses are analyzed by method of Hilbert-Huang transform(HHT).Meanwhile,the physical meanings embedded in the Hilbert spectrum of structural dynamic response and its resolution are compared with those of Morlet wavelet spectrum.It has been demonstrated that under the regular harmonic input,the Hilbert spectrum of structural dynamic response can differentiate between stationary response and transient response of structure,and the damage-induced change of structural dynamic properties can be identified by the resulted transient response.While under the irregular seismic input,due to the complexity of the input,the Hilbert spectrum cannot differentiate between the station- ary and the transient response of structure,however,by virtue of the instantaneous energy distribution charac- teristics of Hilbert spectrum,a type of predominant instantaneous frequency(PIF)is defined,whose temporal variation can describe the damage-induced change of structural dynamic properties to some extent.