Updating the failure probability of miter gates based on observation of water levels

Hydraulic steel structures, especially lock gates play a significant role in keeping navigation traffic uninterrupted. After a few decades of operation, many of the welded joints may suffer various degrees of deterioration, primarily due to fatigue. To economically combining crack inspection with a scheduled maintenance of the movable parts of the gate, it is valuable to predict inspection time of the welded joints using the historical operations of the gate, i.e. the variation of water levels. Updating failure probability of welded joint is mature in the offshore industry, but it is rarely applied for inland navigation lock gates where the contribution to fatigue failure comes from the variation of water pressures during operation of the lock gates. The scope of this paper is to predict the inspection time of a welded joint using the observed water levels from the operational history. The updating of the failure probability is done for three inspection techniques, considering annual probability and repair decisions. The results show the effects of critical annual probability and the probability of detections (PODs) on the update failure probability for a welded joint.