Optimal inspection and repair scheduling for mitre lock gates

Abstract

Hydraulic steel structures, especially lock gates, play an important role in inland waterway transport infrastructure. Navigation lock gates are normally designed to last for 100 years. However, after a few decades of operation, many welded joints of steel mitre gates may suffer deterioration and unexpected failures, occurring primarily due to fatigue. As emergency repairs are costly, time-consuming and disruptive, optimising the operation and maintenance plans of mitre gates is necessary. Risk-based inspection planning has been used for marine structures but is seldom applied to inland navigation lock gates. In this paper, 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. It was found that the total expected cost of inspections performed at regular time intervals was generally higher than inspections performed when a certain annual failure probability threshold was reached.