Hilbert–Huang Transform based method for monitoring the crack of concrete arch by using FBG sensors

Little cracks in civil engineering structures may be the first indication of a serious defect. Crack monitoring of concrete is crucial for the integrity of civil engineering structures. In this paper, fiber Bragg grating (FBG) sensors were used for monitoring the crack of two CFRP concrete composite arches in MTS loading and unloading test. During the test, time series of strain data can be obtained by different FBG sensors. At the same time, initial cracking time is observed and recorded by the experimenters. After the test, a method based on Hilbert–Huang Transform (HHT) is used for determining the cracking time, which take the advantage of Empirical Mode Decomposition (EMD). The test results indicate that the HHT based method can be used to determined the cracking time when using different pasting method, even if the fix location of FBG sensors is not very accurate, and the 2nd IMF is better than other IMFs in crack monitoring, which is selected as a criterion in crack monitoring.