Authors: HAMR – Martin Raniš, David Kubík, Tomáš Kosnar
In the year 2014 we were approached by Mr Bouška, a passionate cyclist and a current deputy mayor of Mladá Boleslav, to propose sketches of five different bridges and transborders for the city. Though the design for the bridge for the river Klenice, which had won the representatives over, had to stand by for a while in order for sufficient financial funds to be gathered, all circumstances worked out in the end and the bridge now stands in its place.
The bridge, designed for pedestrians and cyclists, is very specific in terms of its design and construction. In the case of rising water levels and the threat of a flood, the footbridge can be manually pulled upwards and out of its concrete foundations into a safe height. This unique function requires a rather rare construction. In that sense, we are very grateful that the city of Mladá Boleslav gave us the opportunity to take part in such project.
A bold construction of a wooden pyramid-shaped frame hovers over the bridge. Four pine-wood columns support other secondary constructions, onto which the bridge itself can be raised via a lever block-and-tackle mechanism. In order to make the lifting as convenient as possible, the construction of the footbridge had to be extremely light. Thus we opted for the classic Howe’s truss, favoured since the rail boom era. It is a truss with two kinds of construction. One is made out of crossed wooden compression members, second is made out of steel thread bars in order to resist tension forces and to link the truss’ chords together. The steel tension rod thus naturally separates the role of wooden and steel components in the entire length of the construction. The footbridge itslef is made out of larch wood. The bridge deck is constructed as a grid of 20x60mm timber profiles. The life span of the construction is significantly inceased thanks to the protection of wooden horizontal components against water, as well as titan-zinc detailing.
The bridge provides a link between newly built pedestrian and cyclist paths and thus, thanks to its position, it offers an ideal solution to optimalising the city’s infrastructure.
Photographs: René Volfík