Footbridge over the River Mogent in Montornès del Vallès
Montornès del Vallès is a municipality of 16,000 inhabitants in the metropolitan area of Barcelona.
The two urban areas or Montornès Centre and Montornès North, which are located over a kilometre away, are on opposite sides of the River Mogent, which crosses the municipality. Up until now there was only one bridge to cross the river so the main goal of the new footbridge was to provide a new pedestrian path to reduce the length of the displacements between these two main districts and at the same time to offer a friendlier route for pedestrians and cyclists.
In essence, the project consists of three large objects: the deck over the river and the two access ramps.
For the main element of the project – the deck – a simple structural solution of a single 47.7 metre long span Corten steel truss grinder was chosen. The structure is formed by two longitudinal Warren truss grinders linked together at their top and bottom flanges by horizontal Warren Trusses.
This cross section was conceived in such a way that most of the structural depth of the main grinders is set out above the level of deck paving. With this arrangement, it was possible to achieve the maximum clearance over the river bed with minimum height and therefore, allowed designers Alfa Polaris to minimize the length of the approach ramps.
The decking of the footbridge is placed over the lower horizontal truss so that the users walk inside a rectangular tubular element, with a functional width of 3.0 meters and a free height of 2.7 meters; an arrangement that offers a safer feeling against the proximity of the power line cables that cross the river just above the deck structure.
The partially covered path along the deck deepens the hierarchy of the space by clearly highlighting the difference between the approaches and the spanning section that flies over the river. From outside, the deck appears as a forceful object, clearly differentiated from the ramps, and big enough to compete with their imposing volume. The contrast between these elements was accentuated by the choice of their main materials — Corten steel for the deck and granite stone for the filling of the gabions on the approaches. The result is a structure that is shown as a huge object placed in the air, which seems it has no contact with the rest of the work, as if it was levitating.
Balustrades in the footbridge were cladded with XTENSION Architectural Mesh by The Inox in Color (www.theinoxincolor.com). XTENSION works as a safety system, providing an architectural accent to footbridges with lightness and transparency at horizontal view as required by project architects.
For the ramps, a zigzag configuration was achieved, taking advantage of the provision of the prescriptive level landings. This was done to avoid the formation of long single slopes. This zigzagging arrangement has also meant as a result that the retaining walls adopt broken shapes that break the monotony of the long parapets that would have resulted if a more linear solution had been chosen.
The street lighting along the deck is formed by linear warm white colour LED lights. These are mounted inside special Corten steel elements and are fixed and oriented along the axis of the diagonal bars of the main trusses.
During the night this arrangement provides a pleasant illumination along the footbridge and highlights the sought irregularity of the structure. Along the ramps the street lighting is solved through lampposts, also with LED technology, and the same warm white colour temperature.
The choice of the pavements was also made with the intention to emphasize the contrast between the deck and the approach sections.
Over the footbridge, synthetic timber —made from recycled wood products that are mixed within a polymeric matrix— was chosen. This provides a warmer and more tactile feeling close to that of natural wood, without the periodic maintenance the latter requires. On the other hand, along the section where the wood decking was installed, a longitudinal one meter wide strip of electro welded Corten steel grating was placed, which provides a safer passage for the cold winter mornings when timber becomes extremely slippery. For the ramps, a pavement of concrete slabs was built.
Xavier Font, Founder of Alfa Polaris commented: “We believe that, although the design of this project has been strongly conditioned by the site requirements, we have achieved the goal of providing a new connection with a reduced initial investment and solutions with low costs of maintenance, providing a proposal with a careful design, which enriches the landscape quality of the river area and contributes to improving the quality of life of its users.”