基于随机减量法得到自由衰减时程，并进行去噪，后小波变换，拾取小波脊线处的幅值以及相位信息，提取自振频率及模态-The random decrement method based on free decay time, and after denoising, wavelet transform, wavelet ridge is picking up the amplitude and phase information extraction, natural vibration frequen