An essential part of the Nieuwe Sluis are the four lock gates that open and close via rolling guidance. In addition, two of the lock gates function as a backup should one of the other gates need to undergo maintenance or have suffered damage (due to a collision). 

A comprehensive portfolio
The design of the lock gates adds yet another large lock project to Iv-Infra’s portfolio. Iv also designed the lock gates for the Panama Canal and the IJmuiden Sea Lock.

Because of their immense dimensions, the lock gates of the Nieuwe Sluis in Terneuzen, like those of the projects mentioned above, are based on the same principle as roller shutters, but all the gates are unique. While in Panama, the design is strongly influenced by the necessary earthquake resistance; the IJmuiden design is characterised by the area’s limited space, which demands ingenious solutions to build the world’s longest lock gates.  

Wave forces
In Terneuzen, the wave forces on the lock gates from the Western Schelde estuary (Westerschelde) is specifically a unique aspect. The gates are designed to be strong enough to absorb waves from passing seagoing vessels without causing damage or fatigue. In addition, a centrally positioned rolling guide ensures the gate can open and close under high stresses. Not only are the lock gates for Terneuzen unique, but also the bascule bridges. In terms of span, the two bridges are among the largest in the country, comparable to the Erasmus Bridge and the Van Brienenoord Bridge in Rotterdam.

The gates must function amid waves and extreme conditions, and so must the bridges. In this respect, climate adaptation (how we deal with climate change) is reflected in both designs. The bridges have an extraordinary mechanism and operation because in a so-called ‘perfect storm’, the bridges will not remain closed but instead be opened. “In the event of a storm surge, a tidal wave can occur, potentially severely damaging the bridge or sweeping it away in a single strike. Wave loads are much higher than wind loads; the bridge cannot be designed according to wave criteria”, says Michel Koop, Head of the Steel & Movable Structures sector at Iv-Infra. “To prevent this kind of scenario, the bridges will be opened and secured accordingly when the weather forecast predicts a storm surge. The bridges can also withstand high wind loads.”

Working with BIM
Digitalisation is an essential factor in the design phase of the bridges and gates. Therefore, all designs are placed in a Building Integrated Model (BIM): an information model in which everything is spatially represented. This helps facilitate maintenance and management when the Nieuwe Sluis is in operation. Dennis: “All components are included, and additional data and information can be added. Moreover, the BIM model is a practical way of demonstrating the correctness of all the interfaces.” All disciplines within Iv-Infra have been included in this model to ensure all sections and components fit seamlessly. “We already used the BIM model in the preparation phase”, adds Michel, “to present the phases of the work to the client so that throughout the project, the client could gain an increasingly completer picture of the entire lock.”

As far as maintenance is concerned, Iv-Infra will continue to be involved in an advisory capacity. This aspect was also taken into account in the engineering phase, especially given the size of the two bascule bridges. “The huge dimensions meant that maintenance needed early consideration. The components of smaller bridges are always relatively easy to replace. But, replacing, for example, a hinge pin of a hydraulic cylinder on a bridge of this size is quite a challenge, also because of the weight”, says Michel. “As designers, we must demonstrate in detail that sufficient space is available to reach and replace components. Sometimes we will also need to develop the appropriate tools, as these may not be commercially available.”

The best of both worlds
The Nieuwe Sluis in Terneuzen is an exciting, cross-border collaboration between various Dutch and Flemish institutions and companies. The client, the Flemish-Dutch Scheldt Commission, consists of the Directorate-General for Public Works and Water Management (Rijkswaterstaat), and the Flemish equivalent: The Department of Mobility and Public Works, because of its economic interests on both sides. The Sassevaart consortium comprises major Belgian and Dutch construction companies such as BAM, DEME, Stadsbader and Van Laere. 
This Flemish-Dutch combination appeals to Dennis Alsemgeest of Iv-Infra. As Lead Structural Engineer, he has been involved for many years in the design of the four gates installed earlier this year. “You can see the input from both countries in this project. Both in the contract, the technical requirements for the gates and the design elaboration. The Netherlands and Flanders have considerable experience in constructing sizeable hydraulic engineering projects, such as the Afsluitdijk (a major dam in the Netherlands), the IJmuiden Sea Lock and the Kieldrecht Lock in Antwerp. It is genuinely fantastic to see the knowledge and skills of both countries coming together in this project.”

The Nieuwe Sluis Terneuzen has proved to be a unique project in which mutual communication and close collaboration in the integral design team of the Sassevaart consortium has played a crucial role.