Wooden cable-stayed bridge over A28 near Harderwijk

ZJA designs wooden cable-stayed bridge over A28 near Harderwijk.
"The design is even more beautiful than we had hoped", said Rob Daamen, Traffic and Transport Councillor of the municipality of Harderwijk.

Heijmans Civil BV from Nijkerk may build the much discussed cycle bridge over the A28, connect-ing the neighbourhoods Drielanden with Harderwijk Centre. For this purpose, a contract was signed today between Heijmans and the municipality of Harderwijk. Heijmans won the municipal tender procedure, in which four other companies competed.

The cycling route
The design includes a bike trail that crosses a bridge over the A28 motorway and then a bridge over the pond, connecting the southern Zeepad with the northern Zeepad, and so linking the area south of the A28 with the centre of Harderwijk via a short bike connection. In addition to these two bridges, a third simple slab-bridge over the narrowed portion of the pond is also part of the tender.

The northern Zeepad runs along the former Zuiderzee, all the way to the centre of Harderwijk and the old fishing harbour, where even today some “Botters” - old fishing vessels - are moored. The requirements of the tender place this Botter and the related history of Harderwijk central in the de-sign. This principle has been thoroughly considered by ZJA and then translated into the design. The design of the wooden bridges was arrived at in close cooperation with timber firm Wijma from Kampen, a Dutch timber company which - as one of only a few - manages self-sustainable forests in Africa.

The bridges
The first of the three bridges is a wooden cable-stayed bridge over the A28 with a length of about 76 meters and a free span of about 50 meters. The second bridge is located in line with the first bridge and has a length of approximately 78 meters, distributed in spans of approximately 7.8 me-ters. The third bridge is a small slab-bridge with a span of 10 meters, located immediately north of the two other bridges.

The design of the cable-stayed bridge is a new eye-catcher for Harderwijk. Passing this object over the A28 should result in a moment of recognition for the motorist, which welcomes him to Harderwijk. This bridge provides two great experiences: one from the car when under-passing with high speed and secondly one when cycling or running over it at low speed. Consequently, there are two totally different ways of experiencing the bridge: the experience of large scale seen from the
motorway, wherein the silhouette and the appearance are of interest, where the details are lost and only the broad lines remain. Then there is the experience of the small scale, of the detail, in transition by bike or on foot.

The silhouette
When approaching from the A28, the silhouette of the bridge is strongly associated with the silhouette of a Botter, with its asymmetric sail and rigging distribution and the characteristic slightly sloping wooden mast. The main structure of the bridge is constructed from Azobé, a wood typical to engineering and marine applications. The wooden deck is suspended by cables, hanging from two massive wooden pylons, depicting two Botters, with the wooden deck line sharply contrasting against the lighter coloured balustrades.

Material selection
Maintenance-free and "aging gracefully" are central to the future value and sustainability of the three bridges. The materials have been chosen in such a way that the bridge will look better with age and that inevitable minor damages are included in the bridge in a natural manner, and do not take shape as scars. As a result of weathering, the wood used will only turn better. Besides that, the preserved steel railing will remain unchanged, unaffected by the elements and so form a more beautiful contrast with the wooden deck.

Project: 745