关键词: 桥墩系统, 冲刷, 希尔伯特黄转换, 经验模态分解法, 间断性准则

Abstract:

The objective of this research is an attempt at applying the empirical mode decomposition (EMD) and Hilbert-Huang transform (HHT) to decomposing the vibrating signal and analyze the frequency spectrum of the pier foundation. To receive the vibrating signal produced by the moving heavy vehicles, the devices set up for detecting the signal on one side of the deck of the bridge. In EMD method of decomposing the vibrating signal from the pier, the intermittency criterion is used to obtain the better obviously components and improve the judgment of the HHT frequency spectrum. From this study, the process of analyzing EMD, which may produce mixed phenomenon in mode, will result in the frequency loss and the shortening in reading range in HHT graph. Through appropriately applying the intermittency criterion, these problems mentioned above can be solved and receive the higher confidence on the judgment both in HHT graph and in the marginal frequency graph. Besides, the result of HHT graph proves that the instant frequency variation in direction Y of the pier system is regarded as the frequency range between 1-4 Hz. And the marginal frequency graph shows that the frequency energies of P1 and P2 are centered around 2.5 Hz and 1.7 Hz. So, the stiffness of the foundation P2 obviously lower than that of the foundation P1. According to the result, the bearing capacity loss of P2 can be showed clearly by using HHT method.

Key words: pier foundation, scour, empirical mode decomposition (EMD), Hilbert-Huang transform (HHT), intermittency criterion