High quality hydraulic structures

In the Binnenspuikanaal of the IJmuiden lock complex, construction is underway on the Selective Withdrawal, an inventive construction that returns saltwater to the sea. Because of this project, existing mooring facilities and waiting places must be relocated to the south side of the North Sea Canal. To this end, Beens Groep is realizing three footbridges and a new jetty construction in accordance with high quality standards, commissioned by Van Hattum en Blankevoort. 

Initially we were asked to make an offer for the scaffolding, begins Peter Melis, business manager at Beens Groep. "After being awarded, a follow-up order came almost immediately for the realization and installation of three footbridges. And there was also some urgency with that, because it had to go along with the phasing." The footbridges connect the new moorings for commercial shipping to the mainland, while the jetty is intended as a mooring location for the working vessels of the Rijksrederij, part of Rijkswaterstaat. These vessels are now moored at a temporary location.

From design to implementation

Beens Groep is responsible for both the design, production and assembly of the steel hydraulic structures. "Of the footbridges a Preliminary Design was already available, of the scaffolding only the functional requirements," says Maarten Vos, work planner at Beens Groep. "Because of the high requirements, we paid a lot of attention to the design by flying it in such a way that the work outside is kept to a minimum. Consequently, there is plenty of prefabrication. The walkways, each 25 meters long (and 1.5 meters wide), are already assembled and coated in their entirety at the factory. They were delivered to the project ready-to-use and could thus be assembled directly on the pipe piles and substructure we had previously installed. Because of that good preparation, the assembly took only three weeks."

Dismountable

The scaffolding structure is considerably more complex in nature. The scaffolding is 100 meters long, 4 meters wide and has a platform on which a truck-mounted crane has to be able to level off. "It is quite a tour de force in terms of construction and dimensions, all the more so because the structure is also completely demountable," Peter states. "The latter was an additional requirement from the Department of Public Works, both with a view to circularity and in the event of a collision where only one section needs to be replaced." Because of that demountable nature, Beens Groep limited the number of welded joints. Maarten: "Nevertheless, welding is still done in the work. Mainly to accommodate the tolerances of the 33 tubular piles we previously installed. We do that with an oversized flange that is welded off in the work."

High quality 

The scaffold is extremely slim in shape. "This is due to the unique substructure construction," Peter knows. "Normally you stack the transverse and longitudinal beams on top of each other, here they are integrated into each other." Maarten adds: "Furthermore, we use special 'walking grids' of 10 centimeters high on the part where the truck-mounted crane has to be able to align. The longitudinal section where the truck-mounted crane does not come will be equipped with 5-centimeter gratings, but even these can easily support the weight of a car." High quality standards underlie the entire construction of both the scaffolding and the walkways, including 1.4 of the Guidelines for the Design of Art Works (ROK).

The scaffold was transported to IJmuiden as a construction kit in fifteen numbered sections. "The assembly may seem like a simple 'job,' but it is far from it," says Richard de Boer, superintendent at Beens Groep. "We deploy our largest pontoon with 110-ton crane and largest working vessel for this. It requires a sophisticated interplay between man and machine. After assembling the sections, we install all the utilities on the jetty and realize a small storage area cum workshop for the benefit of the work vessels of the Department of Public Works." The walkways have been in use for just under a year now, and the jetty is scheduled to be delivered by Beens Groep at the end of this year.