Kattendijk Lock – Damage to a successfully renovated structure
SBE completed a study of the renewal of the Kattendijk lock in the Port of Antwerp several years ago. The lock was build in the early 19th century and after being out of service for decades, was due for a renovation. The aim was to reintroduce the lock once the renewal was completed, mostly for private and non-commercial ships. This project formed part of the revaluation of ‘het Eilandje’, one of the historic districts of Antwerp.
The downstream lock head got new steel lock doors (mitre gates) and a new steel bridge. The Contracting Authority and historical services opted for the upstream lock head to be replicas of the original wooden mitre gates. The study of the wooden gates was a challenge for SBE as such assignments are rare in the modern market.
The original design needed to be followed quite strictly. In the past the wooden gates were operated manually but the new gates are operated by use of mechanical jacks, similar to the modern steel mitre gates. With some effort, SBE found a way to couple these modern jacks with the original wooden gate geometry.
The Contracting Authority provided the necessary data to complete the study. A thorough preliminary analyses of the new situation for the lock, specially for the new hydraulic conditions was completed by the client. The new method of operating the lock gates differed from the original method. The Client was very careful about this change and the possible impact it might have. The result of the preliminary analyses resulted in a set of load cases which was presented to SBE to use.
The design of the wooden gates with all this information was then commenced. A manufacturer, specialised in wooden gates manufactured the replica gates. Another specialist in mechanical components manufactured the jacks and the rest of the mechanical components. Everything was installed on location by the general contractor. The whole was tested, approved and subsequently opened for service. In brief, a successful project.
6 months into service of the lock, SBE received a message; a strange noise could be heard during the opening of the wooden gates. All stakeholders of the project completed a site visit to try and identify the issue: the client, contractor, control officer and SBE as the engineering office that completed the Detail Design.
One wing of the mitre gates was lifted out of the water for inspection. Failure of the diagonal steel tendon was witnessed immediately. It was broken in half (which had occurred on all four gate wings). The upstream lock head had two sets of mitre gates which enable SBE to do some testing on the second set of lock gate to find a possible cause. After some simulations on site, a hydraulic head over the gate during opening was noticed. This hydraulic head was much higher than was predicted in the theoretical analyses of the client.
This higher hydraulic head during opening, resulted in higher than anticipated torque in the gates which caused the failure of the steel tendon.
A solution was soon found in adapting the movement of the gate. A small alteration in the starting speed resulted in a significant decrease of hydraulic head. The broken tendons could also be repaired quite easily.
Click here for more information about this project.