Michiel de Ruyter bridge: constructively challenging

The Michiel de Ruyter Bridge is anything but a standard drawbridge. In order to be well prepared for the tender, the 2KA consortium called in the expertise of Ingenieursbureau Boorsma at a very early stage. Together with the construction consortium, the specialist in movable bridges was able to translate the ingenious (constructive) ideas into a feasible whole. Together with Anne Jan Breimer of Ingenieursbureau Boorsma, we zoom in on three technical challenges.

Engineering firm Boorsma has extensive experience in engineering movable bridges of all shapes and sizes. "It ranges from small drawbridges for cyclists and pedestrians to projects of enormous size, such as the bascule bridges at Sluis Terneuzen," says Breimer. The Michiel de Ruyter Bridge is a special project for the firm. In several ways. "First of all, the bridge is being realized a stone's throw from our site in Urk, and in addition, our scope for this bridge is quite extensive. For Knipscheer Infrastructure, we did the engineering of the civil substructure and the braking and guidance works, and for Knook Staal en Machinebouw we did the engineering of the steel construction and the movement work."

Forces

According to Breimer, the advantage of such a broad scope is that everything can be arranged in-house. "Coordinating the interfaces is then relatively easy. Our task was mainly focused on fulfilling the image quality plan as well as possible within the set frameworks and the EMVI promises of the building consortium. Building without a cofferdam on the water was one of them, a conscious choice to minimize disruption to shipping. We were already familiar with such a methodology as a firm because of a similar concept at the Vecht Bridge." 

The "cofferdamless concept" for the Michiel de Ruyter Bridge assumed a 115-ton precast substructure for the bridge basement that was positioned on the steel tubular piles in the water. Next, a concrete floor was poured that ingeniously intervened in the precast structure and had an important role in transferring the overall interplay of forces from the hammer post and cylinders to the steel tube piles. "Consequently, there was quite a bit of reinforcement involved locally," he says.

Construction Seal

From the image quality plan, the choice had already been made for a central hamstring style with one tie rod. "That obviously brings with it the necessary challenges in execution and especially in design," Breimer knows. "We calculated, for example, how much building sweep (pre-distortion) Knook Staal en Machinebouw had to give both halyards at the factory in order to pressurize the bearings in the final situation, with the aim of guaranteeing a fixed position and counteracting the risk of chatter. To ensure that the pre-distortion was also properly included in the traps, Knook Staal en Machinebouw conducted a full-scale test in the factory for this purpose. The pre-distortion is eliminated the moment the traps move upward."

Incidentally, the overweight of about 6 tons also contributes to a positive uplift pressure. "That overweight is possible because of the choice of a hydraulic drive system with a separate cylinder for each fall. When the bridge is closed, the cylinders do not need to be pressurized. The dimensions of the cylinders are matched to the different surface area of both traps. In this way, the pressure in the system is more or less the same and one hydraulic unit suffices."

In total, Ingenieursbureau Boorsma produced nearly 150 drawings for the Michiel de Ruyter Bridge, all from a 3D model, of course. "Eventually we also added the scope of ÆVO to the model, responsible for the electrical installations. That resulted in an integral 3D model, the basis of a successful execution, we may now conclude. A wonderful reference and literally a home game for us as an agency."