| CPC G01H 17/00 (2013.01) | 7 Claims |
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1. A dynamic identification method of bridge scour based on health monitoring data performed by a computer having a processor and a non-transitory computer readable storage medium storing a computer-executable program, wherein when the computer-executable program is executed by the processor, the program causes the processor to perform the method comprising the following steps:
step 1: receiving the health monitoring data containing an acceleration-time curve of a bridge foundation structure in a scour state from a health monitoring system, the acceleration-time curve being collected by the health monitoring system when the bridge foundation structure vibrates, and performing anti-interference factor pre-treatment on the acceleration-time curve;
step 2: by Fourier transform on the acceleration-time curve in step 1, obtaining a frequency-time curve of a bridge scour reference mode;
step 3: determining a value of a significance level value α, wherein step 3 comprises the following steps:
step 3.1: by using a kernel density estimation method, establishing a time-frequency probability distribution model of a bridge scour evaluation reference mode, and transforming a scour reference mode frequency into a random variable which obeys standard normal distribution;
step 3.2: according to the random variable which obeys the standard normal distribution, in combination with a Shewhart mean control chart, preliminarily setting the value of the significance level value α, and obtaining a probability distribution function corresponding to the significance level value α, and establishing a normal distribution probability model; and
step 3.3: performing identification sensitivity calibration according to the range of the preliminarily set value of the significance level value α;
step 4: bringing the significance level value α into the normal distribution probability model, and obtaining an upper control threshold UCL and a lower control threshold LCL of the abnormal warning of a time-frequency change of a first-time scour bridge evaluation reference mode by calculation;
step 5: identifying an abnormal segment in frequency segments of a scoured bridge to be identified:
step 6: identifying an abnormal time-frequency sequence in the time-frequency abnormal segment, wherein step 6 comprises the following steps:
step 6.1: the time-frequency abnormal segment comprising a plurality of time-frequency sequences, identifying time-frequency abnormal sequences in the plurality of time-frequency sequences:
setting identification parameters of the time-frequency abnormal sequence, the identification parameters of the time-frequency abnormal sequence comprising a time-duration ratio parameter PL/U′ of an abnormal reference frequency sequence, a time interval parameter Ts' between two adjacent abnormal frequencies, and a change difference parameter Ms′ of a mean value of scour reference frequencies;
step 6.2: calculating the time-duration ratio parameter PL/U of the abnormal frequency sequence of the abnormal segment:
PL/U=Tab/Tt0
wherein, Tab is the time duration of the frequency sequence exceeding the upper control threshold UCL or the lower control threshold LCL, and Tt0 is the total time duration of the abnormal segment;
calculating Ts of the abnormal segment, Ts being a time interval between two adjacent Tabs;
when PL/U>PL/U′, and Ts<Ts′, it is determined that the time-frequency sequence is the abnormal sequence, and step 6.3 is started, otherwise, it is determined that the time-frequency sequence is normal;
step 6.3: calculating a scour reference frequency time sequence mean value change difference Ms in the time-frequency abnormal sequence:
Ms′|M1−M2|
wherein M1 is a frequency mean value of the time-frequency abnormal sequence, and M2 is a frequency mean value of the normal segment in a healthy state of the previous of abnormal segment with the same time interval;
when Ms≤Ms′, it is determined that the abnormal sequence is in normal signal oscillation; when Ms>Ms′, scour early warning is performed for the abnormal sequence; and
step 7: after completing the scour early warning of the abnormal sequence, repeating steps 5-6 and updating the upper control threshold and the lower control threshold of random fluctuation of time-frequency characteristics of the bridge scour reference mode so as to prepare for the next anomaly identification and scour early warning.
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