First temporary movable bridge for heavy traffic

In Westknollendam the existing movable bridge over the Tapsloot had to be renewed, but without disrupting road and shipping traffic. A temporary movable bridge became the solution, realized by Janson Bridging.

Janson Bridging is a Dutch company based in Hank and a global player in the field of modular, temporary bridges. But the situation in Westknollendam presented challenges for this specialist as well. In less than half a year, the new movable bridge had to be designed, engineered and built. And this in a complex situation and strict laws and regulations. Moreover, Janson wanted a design that could be used in other places in the future.

Designing with multiple challenges

"When designing temporary bridges with the aim of using them more often, there are always additional challenges," says Alex van der Wiel, manager of Engineering Europe at Janson Bridging. "You have to design the temporary bridge according to the principles of the specific project and at the same time take into account still unknown, future requirements and wishes. This requires an extremely flexible design. Here we use the IFD principle (Industrial, Flexible, Demountable). We design standardized bridge elements that fit together precisely and are reusable. An additional challenge in Westknollendam was the time frame. The design had to get there quickly, without losing sight of safety, strength, circularity and flexible deployability."

Modular design in a short time

The starting point for the design was the swing bridge, a maximum configuration with two lanes suitable for heavy traffic and a bicycle lane on either side. This part of the bridge also had to be modular and comply with Janson Bridging's philosophy. "In addition, the bridge had to be able to be opened within two minutes and closed within two minutes," says Bastiaan Hulsbos, commercial manager of Janson Bridging. "An extremely short time for a temporary, movable bridge. Finally, the bridge was located in an N-road, which placed special demands on the bridge due to the traffic passing over it. With all these factors in sharp focus, we started designing." 

Hydraulic spring

An elementary component of movable bridges is the counterweight, which makes the drive lighter. "We could not realize this in the short time frame," says Marcel van Fessem, sales manager of Janson Bridging Netherlands. "Therefore, a kind of 'hydraulic spring' was chosen for opening and closing the bridge, a so-called unbalanced bridge. This involves charging a hydraulic battery in about 15 minutes, which ensures that a large force is developed in a short time to get the bridge moving. Thus, the short opening and closing times were met." 

Van Fessem: "The choice of a temporary movable bridge brought great benefits to Westknollendam and the surrounding area. Shipping and road traffic could continue undisturbed and residents were not plagued with lengthy detour."