Garabit Viaduct (1884) France
The Garabit Viaduct (Viaduc de Garabit) is a railway arch bridge spanning the River Truyère in the mountainous Massif Central region of France.
In the late 1800s, mountainous terrain in the area prevented railways from reaching the south of France and engineers struggled for a workable means of crossing obstacles such as the windy Garabit Valley in the French Cantal department. The task was entrusted to one of France’s most famous engineers, Gustave Eiffel who proposed a wrought-iron arch viaduct bridge designed to deal with the problem of strong winds in the valley by using trusses rather than solid beams. He had successfully completed a bridge with similar technical problems, the Maria Pia Bridge in Portugal, in 1877.
Eiffel chose the truss option as the lightweight and stable open triangular design would allow the wind blow through whereas the heavier solid beams would be less stable and rattle in the wind.
The viaduct was constructed between 1882 and 1884 and opened to rail traffic in November 1885. The structure is 565m (1,854 ft) long and the span of the principal arch is 165m (541 ft). The 448m (1,470 ft) long metal deck is flanked by two masonry viaducts of 46m (151 ft) and 71m (233 ft) in length and is supported by five wrought iron piers the two tallest of which are 80m (262 ft) high.
It carried a single railway line 120m (400 ft) above the Truyere River and was for many years the tallest bridge in the world. However, the construction in 1959 of the Grandval dam on the Truyère created a 28km long reservoir and the raised water level is today 95m (311 ft) below the bridge deck.