基于小波包变换和时变频率的结构地震损伤评估

基于频率变化的结构地震损伤评估方法具有机理明确和精度较高等特点，但传统信号分析方法在时频分辨率上不能同时满足精度要求，导致时变频率不能直接从响应信号中精确获取，影响频率法损伤评估的应用。依据时频边缘条件提出时频谱分析精度评价标准，通过对比不同的信号分析方法，确认具有特定基函数的小波包变换是获取精确时变功率谱的有效工具。提出基于小波包脊的时变频率提取方法，在此基础上依据结构频率的变化可计算结构时变损伤指标，并最终实现结构多维地震损伤评估。算例表明基于小波包变换和时变频率的结构地震损伤评估方法可以较准确地反映结构的整体损伤演变过程和最终损伤程度。应用该方法时仅需要结构的位移时程，在结构动力分析、抗震验算以及实际结构的震害评估中均具有良好的适用性。

Seismic Damage Assessment Based on Wavelet Packet Transform and Time-Varying Frequencies

The seismic damage assessment method based on frequency changes is applied with the advantages such as clear mechanism and high precision, but the time resolution and the frequency resolution can not be accurately meet at the same time when the traditional methods for signal analysis are used. Hence, the time-varying frequencies cannot be obtained directly from the response signals and the application of this damage assessment method is insufficient. The corresponding accuracy evaluation criterion for different signal analysis methods is presented based on the marginal condition in time-frequency domain, and wavelet packet decomposition method with special wavelet basis functions is verified as an efficient tool in establishing time-varying power spectrum on the basis of theoretical and computational analysis. The time-varying frequency extraction method based on wavelet packet ridge is proposed, and the time-varying seismic damage index can be calculated according to frequency changes, furthermore, the multi-dimensional seismic damage assessment can be realized. The examples show that the damage assessment method based on wavelet packet transform and time-varying frequency can accurately reveal the overall damage evolution process and the eventual damage state. This method only requires structural displacement histories, and has superior adaptability on structural dynamic analysis, seismic design verification and seismic damage assessment for actual structures.