Venloa design for a green corridor constructed out of logs over the Greenportlane
The ecoduct is an important link in the ecological connecting zone (EHS) to the west of Venlo and will be realized on the Greenportlane, a new area access road to be constructed for the future work landscape Klavertje 4. The ecopassage, with the deer as its target species, will be combined with a pedestrian and bicycle connection across the Greenportlane and is 25 meters wide in total. The ecoduct is situated at the Heijerhoevenweg, which crosses the (planned) Greenportlane at an angle of approximately 15 degrees. This angular rotation is applied in the ecoduct, so that the Heijerhoevenweg can be retained as a functional line as well as a historical line element. The ecoduct must also make an important contribution to communicating the Cradle-2-Cradle philosophy that is central to the development of Klavertje 4 as a whole and to the Greenportlane in particular. That is why a wooden construction of (native) tree trunks has been chosen that expresses "nature crossing over" in a conceptual and expressive way. The ecoduct must be realized before the opening of the Floriade in the spring of 2012.
The beams are constructed out of 2 to 5 logs, which have a tapered shape. These logs, after removal of the bark, have a diameter of at least 300 mm and the width increases with 15 mm every meter. With a computerized mill the connection joints are precisely cut out, similar to a tongue and groove connection. The logs are stacked on top of each other, turning them 180 degrees every other log. This enhances the strength of the construction.
The thickness of the soil which is needed for the plants and trees determines the height of the construction beams and therefore how many logs are needed. Because the thickness varies, the cross section is asymmetrical. This is why the ecoduct has two slightly different sides. Also important for the height of the construction are the expansions. By placing the columns on an angle we manage to reduce the expansion at its most critical spot: there were the load of the ground is the largest (one and a half meters of soil). Here the columns are put on an angle of 30 degrees. Gradually towards the sides of the bridge the load reduces and the columns are placed more vertically, increasing the expansion between the columns. The structural concept of the asymmetrical deck together with the varying columns gives the ecoduct its specific form and origami-like elegance.