A quiet, high-level ride
Amidst a mountain wilderness, a new highway system rises, featuring Spain’s highest viaduct. Trelleborg's bridge expansion joints provide it comfort and road noise reduction.
For years, motorists and truck drivers have had to endure the slow and tortuous climb from Molledo on the Cantabrian northern lowlands, up the N-611, climbing through the Cantabrian mountains to Palencia, on the Meseta – Spain’s high central plateau. It is a dangerous road liable to traffic hold-ups, delays and accidents, and frequently impassable in the depths of winter. Now the N-611 is all but deserted, used mostly by local traffic. In its place is the new Molledo-Pesquero section of the Autovia de la Meseta, a welcome addition to Spain’s highway system.
The southern section of the Montabliz viaduct.When completed, the A-67 – the Autovia de la Meseta – will provide a high-speed link between Spain’s capital Madrid, located at the geographical center of the country, and Santander, the capital of Cantabria, on Spain’s northern coast.
The highway is being designed and constructed by Ferrovial Agroman, a leading infrastructure company in Spain, and the first section, linking Molledo at 250 meters and Pesquero at 750 meters, was officially opened in January 2008.
It is a triumph of engineering and construction in a rugged and beautiful mountainous terrain, built to cope with high traffic volumes, extreme wind and temperatures, and sensitive environmental concerns, such as noise, visual impact and disturbance to the natural surroundings. Two particular challenges for Ferrovial Agroman were the design and construction of the Montabliz and Pujayo viaducts.
The Montabliz viaduct was the greater challenge: 805 meters long and 150 meters high, it spans an area of outstanding natural beauty in rough terrain. The Bisueña river runs underneath the viaduct, through a deep valley cloaked in ancient oak forest, and home to rare animals. In order to minimize disturbance to the valley floor and natural surroundings (and to minimize visual impact), the viaduct was constructed on four single tapering piers, supporting five deck spans. The central pier, at 140 meters high, is Spain’s tallest, and the viaduct is the sixth highest in Europe.
Ferrovial Agroman used self-climbing formwork to construct the piers. This was a first in construction techniques in Spain. The roadway is a continuous pre-stressed concrete deck, with the piers embedded in the concrete deck. The deck segments are the largest and heaviest built in Spain – constructed at the site, and among the largest in the world.
The viaduct at Pujayo, 420 meters long, also posed similar environmental challenges. The same method of design and construction as that used at Montabliz also allowed for a reduction of road noise and the lowest possible visual impact on an adjacent village.
“Metal-style plate joints tend to be really noisy, and give an uncomfortable ride,” says Juan Carlos Minaya, Marketing and Sales Manager for engineered products in Izarra, Spain, part of Trelleborg Engineered Systems.
With a predicted average daily flow of some 11,500 vehicles, 16 percent of which comprises heavy freight trucks, any further noise reduction over that achieved by the basic structure design would be environmentally significant. At the initial stages of the project in 2005, Ferrovial Agroman approached Trelleborg, asking it to supply data on its Transflex high-movement seismic joints for bridges.
Trelleborg provided a “mobile” section joining the abutments and the bridge decking. The surface design of the Transflex expansion joints plays a vital part in road noise reduction. These joints are the final piece in a series of measures designed to ensure bridge safety and to minimize environmental impact.
“The end result is an impre ssive section of high-grade mountain highway. Driving over the two viaducts, the driver is barely aware of passing ov er our expansion joints, while at the base of the piers, there is hardly any sound from traffic passing some 150 meters above,” says Antonio Nogueira, who is Head of Production of the expansion joints division at Trelleborg in Izarra, Spain. “Mostly, you hear the wind rustling through the forest, and the occasional cry of the Iberian eagle.”
Transflex expansion joints from Trelleborg span the space between the decking and the abutments on viaducts, which form part of the A-67 highway in Spain. They absorb movement caused by high traffic volumes, high winds and contraction and expansion from temperature variations.
“Each expansion joint has two sections,” explains Juan Carlos Minaya, from Trelleborg in Izarra, in Spain. “The first is the bridging module, a strong rubber plate that spans the structural opening between the abutment and the bridge deck. The second is the movement module, which absorbs movements of the bridge deck. Horizontal safety anchor bars strengthen the entire unit and prevent sagging.”
A form of surface patterning that creates very little noise as traffic passes over it has been developed. Transflex 3200 expansion joints are used on the Montablitz viaduct, 12 for each section, weighing a massive 500 kg each. On the shorter Pujayo viaduct, Transflex 1600 joints were used.
For further information, please go to:www.trelleborg.com/transflex