Ulla River Viaduct
The Ulla river viaduct is a composite (steel-concrete) railway bridge, located over the Ría de Arosa in Spain, in a natural environment of extraordinary beauty.
The bridge blends in a discrete and elegant way thanks to the mix of colors achieved by the light pearl gray of the concrete and the light green of the paint applied to the truss, that melt with the colors of the forests and river in the surroundings.
The structure is shaped by a continuous composite truss, with a variable cross section depth, with double composite action in the zones with negative bending moments. The viaduct has a total length of 1620 m, with a central section, over the river, reigned by three large main spans of 225+240+225 m and a standard lateral approach span of 120 m, being the main span a world record of its type.
The five main spans, with variable cross section, have a total depth of 17.90 m in the support section and 9.15 m in the center of the span. The four central piles, with a carefully designed cup shape, are rigidly linked to the composite truss of the deck.
The truss, that follows a Warren layout, was defined in 15 m segments, with a separation of 6 m between the nodes of the top chord, and a 45-degree configuration for the diagonals of the truss in the zones with constant depth of the cross section. The chord and the diagonals are formed by
hollow sections, with a width of 0.80 m and a height of 1.00 m (1.20 m for the bottom chord). The top and bottom slab are executed on site, and the bottom slab is extended beyond the limits of the negative bending moment zone, to provide a formal closure (with no structural function) to the section, that helps to improve the aesthetic of the viaduct, and facilitates the inspection and maintenance jobs.
The piles on the central zone, placed in the river, were built with the help of a temporary system of pontoons and sheet piles, in a double ring configuration, which made possible the execution of the foundations of the piles.
The steel truss was built, coordinately, in four different workshops across both Spain and Portugal. The main spans of the deck were built from the piles, following a balanced cantilever methodology. The lateral spans were placed using a heavy lifting technique in one of the sides of the viaduct and launched in the other side.
WORK SCOPE:
- Detailed Design and Project Management
- Property: Spanish Ministry of Public Works. Railway Bureau
- Builder: Dragados S.A.-Tecsa Empresa Constructora S.A. Joint Venture
- Ending Year: 2015
TECHNICAL DATA:
- Composite truss with double composite steel and concrete action
- Overall length: 1621 m.
- Span lengths: 50+80+3x120+225+240+225+3x120+80 m.
- Width: 14 m.
- Maximum piers height: 60 m.
World Record in its typology; Special Mention "Awards for Outstanding Structures 2006"