The interesting thing about a good footbridge is its propensity to cross challenging places with minimum effort.
Luxembourg likes to allow its designers to test their mettle on elements of infrastructure. Not for them the standard components to be stamped out of a production mould and applied to all places regardless of context in the name of branding and some questionable concept of cost saving through repetition. My earlier visit saw Luxembourg successfully challenging the principle of minimum interchange and, having briefly enjoyed one such, on this occasion and in anticipation of a new project, I returned to look at three very different footbridges in three very different settings.
In looking at bridges a few things come to mind. Bridges are there to overcome obstacles, and so building them is not going to be easy and must surely inform the design. With footbridges the span is carrying little more weight than itself and as such, can be as elegant as considerately deployed materials will allow. In most cases only the supports have any chance of incurring unwelcome forces, be they occasional floods or derailed vehicles, and the necessary resistance could easily be of a scale that is out of balance with the span. To make both span and supports combine with visual comfort, in harmony with their surroundings and providing an experience to be enjoyed, while still being able to be constructed in often unusual conditions, is the art and the function of the bridge team.
The clever thing about the Pont Adolphe cycle bridge in Luxembourg city is surely its location. With the deck of the bridge now full of new tram lines, the cyclist, and the more interested pedestrian, are now offered a weather protected trip through the bowels of this historic bridge. The single beam, sculpted to lighten its appearance from the Pétrusse valley below, is suspended from the underside of the deck and reached by ramps and stairs inserted in the urban and parkland landscapes and through the buttresses. These cavernous approaches avoid the subway feel, and the journey across the valley is peppered with magnificent views of the old city. At night the new bridge returns the favour to the old stone structure, gently lighting the arches from within. While it would appear to require an extraordinary feat of lifting to insert the beam, it seems that instead it was lowered through the deck during a major renovation of the original stone bridge. The result is an elegance that while uniquely modern, nicely complements the structurally adventurous span of the original.
At Esch-sur-Alzette the construction and visual difficulties are of a very different nature, with limited ground from which to hoist a deck and a very complex railway environment in which a simple bridge would struggle to be appreciated. Here the designers have considered the potential of an open monocoque structure, to maximise the spans and add a level of visual interest by accentuating the contrast with the context. This is a bridge that has won awards for its design and from a purely visual perspective it’s not difficult to see why. But closer inspection is a little disappointing, as the structure is not monocoque but a clad rigid steel frame, and the goal of external visual interest has come at the expense of the experience within.
Grenzbrucke at Bivels, at the border of Luxembourg and Germany, is surely at the other end of the scale, a bridge so simple and so clear that it is impossible to fault without resorting to pedantry. The setting needs no embellishment, the steep banks of the Our valley so complete that any attempt at clever human intervention would be immediately redundant. Rightly the designers have left well alone, and provided a bridge so pure, so devoid of unnecessary detail, so subtle in colour and simple of form that it quiets the heart to see and to use. I like to imagine that it was floated up the river, the steel legs sunk slowly into the river bed, the span rotated and hoisted on barges to rest gently on the old piers that were found on the river bank, arriving and remaining without fuss. But I have no idea.
So, three very different bridges with three very different ways of addressing the context, the span, the installation and the experience, and so answer the comparatively simple question of getting from A to B. For me, the most successful results are where the designer, the engineer and the contractor are evidently working in balance, answering all the nuances of the A to B question, and coming up with answers that truly respond to the context, the complexity and the ambition, together.