This Corten steel footbridge arches across a new bypass in Spain to connect the small town of Sant Pere Sacarrera with a network of woodland pathways (+ slideshow).
Spanish civil engineers Alfa Polaris designed the footbridge to link two banks that are both at different levels, creating a safe pedestrian crossing that doesn't disrupt traffic flow.
"The client not only wanted to provide pedestrians a pleasant user experience, but also carry out an attractive design that would improve the visual experience of the drivers," said the design team.
Formed of two truss girders, the asymmetric bridge is made from pre-weathered steel that will resist any further corrosion. The deck comprises a row of timber slats.
The northern end of the bridge is positioned higher and features a zig-zagging ramp to make up for the slope, while the southern side is a square platform.
"[This] creates a sort of balcony piazza that provides users great views over the town and its surroundings," said the engineers, who previously designed a similar Corten steel footbridge elsewhere Spain.
Low-maintenance LED lamps light the bridge at night.
Photography is by Xavier Font.
Here's some more information from the designers:
Sant Pere Sacarrera Footbridge
This footbridge over the new bypass of Sant Pere Sacarrera is part of an Y-shaped itinerary that links the town centre with two footpaths that give access to a forest area and were interrupted by the new road.
The client not only wanted to provide pedestrians a pleasant user experience, but also carry out an attractive design that would improve the visual experience of the drivers, avoiding, however, luxurious solutions.
The aim was to get a proposal with reduced whole life cost and environmental burdens. For this reason the design team proposed a Corten steel truss girder structure - very efficient from the structural point of view and whose rusted skin protects itself from further corrosion - for the deck; the use of LED lamps - with long life span and energy efficiency - for the street lighting over the footbridge; and polymeric timber - with almost no maintenance - for the decking over the structure.
The design of the new footbridge was strongly conditioned by the asymmetric shape of the cross section of the road trench, marked by the different level of the two banks. A footbridge composed by two elements was proposed. The main one is a two span continuous deck formed by two Warren truss girders with variable depth, linked together at bottom flanges by transversal beams. The latter, in turn, give support to the variable wide polymeric timber decking through longitudinal joists.
The main span of this element crosses the road, while the second one remains integrated to the north abutment, where a zig-zag ramp raise its level and therefore helps reduce the longitudinal slope of this element.
The second element is a square platform integrated to the south abutment, which creates a sort of balcony piazza that provides users great views over the town and its surroundings.
The main girders have a slight curved shape in elevation and their depth varies, being maximum at the north end - where the deck width is minimum - and minimum at its south end - where the deck width is maximum.
Since the upper chord of the truss has no bracing, in order to prevent it from lateral buckling, the designer improved the torsional stiffness of the bottom chord by giving it a hollow box shape, reinforced the lateral stiffness of the web members and increased the width of the top chord, to which an inverted U shape was given. This allows enough room for the lights to be embedded in it.
High efficiency low maintenance LED technology lamps were installed on each of the bays of the truss. This solution not only provides an agreeable street lighting along the crossing, but, by means of the combination of light and shadows, in the night it highlights the beauty of the structure.
Project name: Sant Pere Sacarrera Footbridge
Location: Mediona, Catalonia, Spain
Design: 2007-2008
Construction: 2011-2012
Client: Diputació de Barcelona
Concept design and engineering: Xavier Font, Alfa Polaris
General contractor: Excavaciones y Construcciones Benjumea, S.A
Structural system: Continuous Corten steel Warren truss girders