Operation conditions monitoring of flood discharge structure based on variance dedication rate and permutation entropy

Abstract

There has been a growing concern on how to monitor the operation conditions of flood discharge structure in recent decades. However, the online monitoring process is always interfered by ambient excitation which leads to inaccurate and uncertain structural characteristic evaluation. To mitigate the interference, a valid operation conditions monitoring method based on variance dedication rate (VDR) and permutation entropy (VDR-PE) is proposed. Firstly, a de-noising method combining wavelet threshold and empirical mode decomposition is used to remove heavy background noises, reducing the interference of ambient excitation to structural characteristic information. Then VDR method is used to realize the dynamic fusion of multi-channel vibration signals, extracting the vibration characteristic of the overall structure in an accurate and comprehensive way. Finally, permutation entropy is used to extract the entropy value of the fused signal. Through evaluating the operation conditions with coefficient of variation, the online monitoring of flood discharge structure can be realized. The effectiveness of permutation entropy algorithm on signal dynamic monitoring is validated by a simulation experiment. Furthermore, VDR-PE method is applied to Three Gorges dam to compare differences between analytical simulation and finite element simulation. The comparison results show that VDR-PE method can be applied to detect the dynamic changes and reveal the vibration characteristic of the overall structure accurately, which provides a new direction for the online monitoring of flood discharge structure.