Treng-Treng and Kay-Kay bridge

The Treng-Treng and Kay-Kay bridge solves connection problems between the cities of Temuco and Padre Las Casas and pays homage to the Mapuche mythology.

On April 2, 2021, the inhabitants of Temuco and Padre Las Casas inaugurated a new bridge over the Cautín River designed to address heavy vehicle traffic and improve the commute for people who use it daily to cross from one city to another.

The bridge was a product of an international competition called on by Chilean authorities to establish a structure that would respond to the growth of the Temuco and Padre Las Casas communities and offer a fluid and safe connection that reduces travel times between both cities. The client mandated a structure that would span over a minimum distance of 230 metres between the shores and the rock walls of the river, avoiding the support installation in the riverbed. They also requested a unique design that could become a visual icon for the metropolitan area of Temuco, the capital and economic hub of the Araucanía Region. 

WSP responded to this call and took on the challenge of reconciling functionality with aesthetics for this 240-metre-long cable-stayed bridge – the first asymmetric bridge to be built in Chile. 

STRUCTURE OVERVIEW

Engineering solutions

During the initial phases of the project, WSP developed three solutions that responded to all the mandates set by the Chilean authorities. Chilean citizens chose the final solution that was designed and implemented through a popular vote, and the new Temuco Bridge is the result. 

The new bridge is the third to be built over the Cautín River and has a prestressed concrete deck of 27 metres wide by 240 metres long and holds two traffic lanes in each direction and one sidewalk on each side for pedestrians and a bike lane. The cable-stayed bridge, which is suspended above the Cautín River crossing a span of 140 metres, is supported by a 72-meter high prestressed concrete pylon; the shape, inspired by a Mapuche legend, represents the struggle of the giant snakes Treng-Treng and Kay-Kay. 

The biggest design challenge

The pylon, which serves as a centrepiece to the structure, was the greatest design challenge. It required a design that combines the symbolism associated with its three bends that invoke the heads of the two mythological snakes representative of the area with its structural function as a channelling element of the forces of the cables towards the centre line of the pylon.

TOP VIEW OF THE FINISHED pylon

Bracing systems

The bridge has two cable-stay systems, one front and one rear. The frontal system is made of two sets of 12 stay cables distributed according to a fan arrangement. As the anchors of the front cables are located on the edges of the deck, transversal diaphragms of prestressed concrete were incorporated to correctly transfer the forces of the cable to the two-celled box. A Finite Element Model (FEM) was made with shell-type elements to study the transmission of the forces from the stay cables to the deck.

The rear bracing system of back stays comprises two pairs of four parallel cables anchored to the retaining blocks. The overall stability of this arrangement was carefully studied, and a Finite Element Model (FEM) was also generated with shell-type elements to analyze the transmission of the tension force of the back stays and the compression force of the deck.

anchoring OF THE stays AT THE HEAD OF THE pylon

Bridge performance

These elements combined form a structure that offers a collection of benefits: accessibility to all types of vehicles and new forms of mobility, ability to absorb the high traffic density of a growing community, guarantee to withstand the high seismic activity in the area. They offer functionality that is not at odds with the aesthetic and unique values mandated by the Chilean authorities and pays tribute to local traditions.

A Bet on Modernity

Although the Treng-Treng and Kay-Kay bridge is the main infrastructure WSP has contributed to the metropolitan environment, it is not the only one. The asymmetric cable-stayed bridge is the centrepiece of a global initiative promoted by the Government of Chile to improve the quality of life of the inhabitants of Temuco and Padre Las Casas. It is part of the Chilean authorities’ commitment to modernizing communication channels and includes 15 kilometres of new roads, two railway bridges, five road bridges, two urban parks and nine kilometres of bicycle lanes.

FRONT VIEW OF THE STRUCTURE

Global collaboration

Colleagues from WSP's Spain and Chile offices worked in collaboration to develop the project, addressing both the conceptual design and the final design and technical advice and inspection in the construction phase. The overall experience was rewarding due to the client's and project's purpose aligning with WSP's vision and mission to enable communities to thrive today and tomorrow. 

The Temuco Bridge project covers technical and social aspects and seeks to improve the quality of life of communities. It exhibits the Chilean Government's commitment to technical excellence that will facilitate the coexistence and development of the entire Araucanía Region and where tradition and progress embrace on the waters of the Cautín River.