二氧化碳相变致裂信号反应谱分析

Response Spectrum Analysis of Carbon Dioxide Phase Change Cracking Signal

为研究二氧化碳相变致裂过程对结构的影响,对现场试验得到的数据进行反应谱分析。首先将速度信号做快速傅里叶变换,分析其频谱特性,然后将速度信号直接微分,运用集合经验模态分解(EEMD)对其进行低通滤波去噪处理,提取主要特征频段的重构信号,获得清晰的加速度时程曲线,并将去噪后的加速度曲线作为输入信号,研究不同阻尼比下二氧化碳相变致裂信号反应谱。结果表明:二氧化碳相变致裂信号频率集中于低频,速度峰值与主频在安全允许范围内,适用于对振动敏感的环境;集合经验模态分解可有效抑制因对速度信号直接微分引起的高频振荡,信噪比可超过25dB;二氧化碳相变致裂反应谱形态简单,峰值对应周期小,有利于结构安全;相对位移和相对速度反应谱峰值随着阻尼比的增大而减小,但峰值对应的周期不变,绝对加速度和标准加速度反应谱峰值在阻尼比不为0时相等,不受阻尼比影响;注意反应谱上对结构影响大的周期,可以在一定程度上保证结构的稳定性。

In order to study the effect of carbon dioxide phase change cracking process on the structure, the response spectrum analysis was carried out on the data obtained from field tests. First of all, the velocity signal is subjected to fast Fourier transform to analyze its spectral characteristics; then, the velocity signal is directly differentiated, the low-pass denoising is performed by using ensemble empirical mode decomposition（EEMD）, and the reconstructed signal of the main characteristic frequency band is extracted to obtain a clear acceleration-time history curve; the acceleration curve after the denoising is used as the input signal to study the response spectrum of the carbon dioxide phase change cracking signal with different damping ratios. The results show that the frequency of carbon dioxide phase change cracking signal is concentrated in low frequency, the peak velocity and the main frequency are within the safe allowable range, and it is suitable for vibration sensitive environment; EEMD can effectively inhibit the high frequency oscillation caused by direct differentiation of the velocity signal, and the signal to noise ratio can reach up to 25 dB; the carbon dioxide phase change cracking response spectrum is simple, and the peak corresponding period is small, which is conducive to structural safety; the peak values of the relative displacement and the relative velocity response spectrums decrease with the increase of damping ratio, but the peak corresponding cycle is constant; the peak values of the absolute acceleration and the standard acceleration response spectrums are equal at non-zero damping ratio, which is not affected by damping ratio; attention is paid to the period in the response spectrum that has a large influence on the structure, and the stability of the structure can be guaranteed to some extent.