# Operation State Evaluation of Miter Gate Based on On-Line Monitoring and Finite Element Analysis
## 4 Signal Analysis and Discussion  
### Analysis of Stress Signals  
The finite element model analysis found that, during the operation of the miter gate, the primary stress is distributed near the gate shaft column and the bottom pivot of the gate, as well as the middle and lower layers of the rear flange plate. Then, we compared and analyzed the finite element simulation results and the monitoring stress data. The specific locations of the stress sensors near the gate shaft column (marked red) are shown in Figure 7.  
Each group of three sensors was installed at the longitudinal, transverse, and connection points of the rear flange plate, and the stress sensors near the gate shaft column and on the first to the 27 th layer on the rear flange plate were selected for analysis. In this paper, the stress signals were extracted from when the miter gate finished closing, filling, draining, and opening during the navigation upstream of the ship on 3 May 2022. Since the operation of the miter gate constantly repeats the action within the above period, this is called the miter gate navigation cycle. The stress signal waveform of the SYM78, SYM79, and SYM80 sensors during this navigation cycle is shown in Figure 8.  
Figure 8: Stress signal waveform in a navigation cycle of miter gate. Figure 7: Schematic diagram of the strain sensor layout on the gate pivot axis of the gate. It is found that the stress curves fluctuate differently under different operating conditions. This paper uses the peak-to-peak stress (wave peak-wave trough) to express the degree of stress fluctuation of the miter gate under each operating condition. As shown in Table 2, the stress peak-to-peaks are recorded by the stress sensors near the gate shaft column in an operating cycle under each working state. Table 2 shows that the stresses at different locations in the axial direction near the axial column from the first to the 27 th layer of the miter gate have a significant difference in each operating condition. The stresses of the locations at the longitudinal and the transverse rear wing flanges fluctuate more under the water filling and draining conditions. The stress fluctuation is relatively low under the closed and opening conditions, as shown in Figure 9.  
Comparing the stress fluctuation at different positions during the gate operation, it is found that the stress change of the first layer of the rear flange plate is larger during the gate's opening and closing. However, it gradually decreases when increasing the number of gate layers. The stress-concentrated locations and magnitude are similar in the water filling and draining conditions. The water level inside the gate rises and falls under the filling water and draining condition, therefore the stress fluctuation of the rear flange plate is more intense, the maximum of which being 318 MPa. The impact of the lower flange plate is smaller than that of the middle layer. The stress fluctuation in the \(X\)-axis direction \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sensors** & **Conditions** & **Closing** & **Filling Water** & **Draining** & **Opening** \\ \hline \multirow{5}{*}{Longitudinal rear wing flange} & SYM8 & 5.7 & 6.8 & 7.3 & 2.7 \\  & SYM13 & 1.0 & 16.7 & 29.3 & 7.6 \\  & SYM80 & 0.4 & 211.4 & 216.7 & 2.5 \\  & SYM84 & 0.1 & 177.2 & 178.7 & 4.0 \\  & SYM113 & 1.4 & 142.8 & 143.7 & 0.9 \\  & SYM141 & 0.2 & 194.2 & 192.8 & 0.1 \\ \hline \multirow{5}{*}{Transverse rear wing flange} & SYM10 & 6.2 & 44.6 & 21.9 & 5.6 \\  & SYM11 & 1.0 & 1.5 & 6.7 & 3.6 \\  & SYM78 & 1.1 & 318.4 & 291.1 & 0.9 \\  & SYM82 & 1.2 & 193.6 & 191.1 & 4.1 \\  & SYM111 & 0.8 & 64.6 & 73.2 & 0.2 \\  & SYM139 & 0.2 & 154.7 & 153.9 & 0.8 \\ \hline \multirow{5}{*}{Crossed rear wing flange} & SYM9 & 7.6 & 25.2 & 7.4 & 6.4 \\  & SYM12 & 4.0 & 13.8 & 18.5 & 10.0 \\ \cline{1-1}  & SYM79 & 1.2 & 96.8 & 100.8 & 3.6 \\ \cline{1-1}  & SYM83 & 0.2 & 19.8 & 18.6 & 6.3 \\ \cline{1-1}  & SYM112 & 0.2 & 51.0 & 30.4 & 0.2 \\ \cline{1-1}  & SYM140 & 1.0 & 17.7 & 18.0 & 0.5 \\ \hline \hline \end{tabular}
\end{table}