Stainless steel in lock gates

Abstract

Gates are an essential part of navigational locks, as they are responsible for creating a water barrier and can be repositioned to allow passage for maritime transit. Most lock gates are made of steel but a recent project in Sweden challenged the status quo by constructing the first stainless steel lock gate. The main question of this thesis aims to investigate the possibilities for the application of stainless steel in Dutch mitre gates and how optimisation through implementing a global arch shape can contribute to the material and weld reduction required to do this. To quantitatively assess the hypothesis of this thesis, Lock Veere was chosen as a case study. The finite element method was selected to simulate the operational conditions of a lock gate.
The first part of this thesis aims to define what needs to be taken into account when designing arch-shaped stainless steel mitre gates. The gate can be positioned in three different setups, which each provide different boundary conditions. Eight different load combinations were defined that could possibly be critical based on size, asymmetrical positioning or repetitive loading. In addition to the operational conditions, the requirements and limits of stainless steel in lock gates were considered.
The second part of this thesis investigates the feasibility and optimisation of the global shape. The effectiveness of shape is based on the loading system of a structure. For a lock, this is the water level difference that results in a uniform load over the width of the construction. Arches are relatively more resistant to this load, which allows for material reduction. Mitre gates have another dominant load situation; a point load with asymmetric support during an obstacle situation. Plates alone are not resistant to this load, so a frame around the plate is introduced. Based on the results found in this thesis, both components seem feasible and allow for further material reduction.
The third part of this thesis aims to prove the effectiveness of a complete gate design by simulating the construction with the operational conditions selected in the first part. The aim of the design was to be as simple as possible in order to meet the demands imposed by stainless steel. The final design allowed for 20\% weight reduction and 30\% weld length reduction compared to the traditional design.
Based on the results that were found, an answer to the main question posed by this thesis can be formulated. For the operational conditions found in Dutch mitre gates, an arch shape can be applied in combination with a surrounding frame. This reduces the weight, number of welds and weld length. For these reasons, manufacturing is expected to be less intensive and maintenance is more accessible due to component reduction. Global shape was thus able to contribute to the optimisation of Dutch mitre gate design. This optimisation through global shape adheres to the requirements for stainless steel. However, this result opens up interesting possibilities for further research on using global shape in combination with other materials as well.