# Operation State Evaluation of Miter Gate Based on On-Line Monitoring and Finite Element Analysis
## 1 Introduction  
Yangtze River shipping is an important shipping belt in the inland navigation from southwest to east China. Three Gorges locks and Gezhouba locks are important water conservancy hubs in the middle and upper reaches of Yangtze River in China which bear the indispensable shipping tasks. As the first hub built on the mainstream of the Yangtze River, Gezhouba locks have been in use for more than 40 years. Many sudden maintenance and planned maintenance occurred due to lock failures during this term, significantly impacting navigation scheduling and transportation channels [1]. Online health monitoring is an excellent method to prevent serious failure, which was widely used on engineering structures such as the Hulan River Bridge, Haikou Century Bridge, and L-shaped structures to improve the safety factor of the systems [2, 3, 4]. For safety monitoring, distributed fiberoptic grating sensors are widely used in current emerging fields, such as, for example, additive manufacturing [5, 6], to obtain the temperature and stress of the structure in real-time. They can also be used for the monitoring of large metal structures by using freeform robotics engineering [7, 8, 9]. In the safety monitoring of the Luzzone hydroelectric dam in Switzerland, distributed fiberoptic grating sensors were implanted in the dam body for the real-time monitoring of concrete temperature and stress changes [10]. Shenzhen Baoan District Xikeng Reservoir also installed an all-fiberoptic type large presentsafety monitoring automation system based on fiberoptic grating sensors [11]. For the structural stability and strong anti-interference ability of the sensing element, the current fiberoptic grating has been widely used in various extensive online structural monitoring engineering systems. To determine the critical monitoring position of the miter gate, [PERSON] performed finite element stress analysis on the ship lock structure and obtained the stress distribution of each part of the lock structure [12]. We obtained the structural stability of the gate by using finite element three-dimensional, non-linear analysis on the lower head structure of the ship lock [13]. Other researchers analyzed the stability through process monitoring and control in intelligent manufacturing [14; 15; 16].  
The repairment of the miter gate of the lock always adopts regular maintenance and post maintenance, which influences the safety of the miter gate and the economic and social benefits of the enterprise. It is necessary to adopt the real-time monitoring method to monitor the operation status of the gate to reduce maintenance and prevent accidents. The miter gate is a large, thin-walled structure, therefore the choice of the installation position of the sensor is significant to make the sensor sensitive to defect changes. Therefore, the stress distribution of the gate can be determined by finite element simulation to help the sensor location. At the same time, if the simulation results are consistent with the measured results, it is also helpful for the analysis of the gate state. Our research aims to construct a feasible online monitoring system of the miter gate and determine the failure reason using simple finite element analysis.  
This paper takes the Gezhouba dam No. 2 miter gate lock as the research object and establishes the online monitoring system of the miter gate. Combining the real-time monitoring signals with the finite element simulation model, we can evaluate the critical areas of stress concentration and crack expansion of the miter gate and provide a basis for the gate fault prevention and maintenance work.