Optimal inspection and repair scheduling for mitre lock gates

Hydraulic steel structures, especially lock gates, play an important role in inland waterway transport infrastructure. Normally navigation lock gates are designed to last 100 years. However, after a few decades of operation, many welded joints of the steel mitre gates may suffer deterioration and unexpected failures, occurring primarily due to fatigue. Since emergency repairs are costly, time-consuming and disruptive, optimising operation and maintenance plans of mitre gates is necessary. Risk-based inspection planning has been used for marine structures but is seldom applied for inland navigation lock gates. A procedure is proposed for inspecting welded joints using observed water levels. Optimal inspection plans are then evaluated by risk analysis, combining failure probabilities and associated expected costs for different events. A mitre gate is used to illustrate the procedure. Total expected cost following inspections performed at regular time intervals was generally higher than inspections performed when a certain annual failure probability threshold was reached.