Viaducto del Malleco
In its time, the Malleco Viaduct was considered the highest railway bridge in the world. It is one of the greatest feats of metal engineering in Chile, and was constructed as part of a vast expansion of the railway network by the state, which the then President, José Manuel Balmaceda, considered fundamental to the country’s economic future.
The bridge was one part of the construction of a railway line between Angol and Traiguén, which was carried out by the State through public tender. The crossing of the Malleco valley presented the main obstacle on this section, as the riverbed runs 110 m below the level of the surrounding plains. This difficulty presented the engineers with the dilemma of going around it or tackling it head on. They opted for the latter and decided to do so at the narrows of Collipulli.
In 1885, the government entrusted Chile’s representative in France, Alberto Blest Gana, with task of calling for proposals for the construction of the viaduct from well known European firms, in accordance with the plans drawn up by Chilean chief engineer of the Arauco railroad, Victorino Aurelio Lastarria. Three French firms tendered plans: Gustave Eiffel, la Societé Anonyme des Anciens Establissements Cail, and Schneider et Cie. O. Le Creusot. The contract was awarded to the last named.
Between 1886 and 1888, the company built the iron frames at its workshops in Europe; they were transported by ship and then by train to their destination. Little by little, the foundations were prepared, and the viaduct was installed between February 1889 and the middle of the following year. The work was inaugurated by President José Manuel Balmaceda on October 26, 1890.
The viaduct’s total weight, measured section by section in the workshops, came to 1,401,344 kg. The bridge was assembled on a large wooden platform, 95 m long. Each stage of placing the bridge on its bases lasted some ten hours, and as the work progressed it became necessary to increase the number of workers, which reached a maximum of about a hundred.
Once the bridge was in place, supported temporarily on hydraulic jacks standing on the pylons and footings, the assembly of the first supports was finished and the bridge was lowered, by use of the jacks, into its permanent position on the great seatings made of cast iron. In February 1890 the assembled structure was slid into place in a highly complex manoeuvre.
This work is impressive by virtue of its size. Its length is 347.5 m, divided into five equal sections of 69.5 m. The bridge rests on the footings at its two extremities and four pylons in between, all of them of steel. The first and fourth pylons are 43.7 m high, the second 67.7 m and the third 75.7 m. The rails are 102 meters above the bottom of the gully.
Subsequently, diagonal reinforcements were placed between the bridge structure and the towers so that the structure would bear the weight of more modern trains. The viaduct can be seen in all its glory from the highway bridge that was constructed parallel to it.