Hilbert-Huang变换在密频结构阻尼识别中的应用

Hilbert-Huang transform for damping ratio identification of structures with closely spaced modes of vibration

Hilbert Huang变换是一种新的数据处理方法,由经验模分解(EmpiricalModeDecomposition)技术及Hilbert变换两部分组成。本文研究此方法对于密频结构阻尼识别的应用。首先对于两自由度系统模型,说明该方法用于阻尼识别的步骤。进而研究存在频率密集现象的高层建筑的阻尼识别问题。上述结果与理论值及由半功率带宽法的识别值进行了比较,对比显示Hilbert Huang方法较传统方法具有良好的识别密频结构阻尼的性能,适用于大型结构的系统识别。

The Hilbert-Huang transform (HHT) method is a newly developed data analyzing method, which consists of mainly the empirical mode decomposition (EMD) and the Hilbert transform (HT). This paper explores the possibility of using the HHT method to identify damping ratios of structures with closely spaced modes of vibration. A 2DOF system with well separated modes of vibration is first analyzed to demonstrate the basic procedure for identifying modal damping ratios of the system using the HHT method. Then, a 36-story shear building with a 4-story light appendage on its top, subjected to an ambient ground motion, is analyzed using both the HHT method and the FFT method. The first four modes of vibration of the structure are closely spaced. The computed results show that the HHT is able to identify the four modal damping ratios but the FFT method gives poor identification results. The first four modal damping ratios identified by the HHT method are close to the theoretical values. The HHT method performed in the time-domain seems to be a very promising tool for system identification of large civil engineering structures.