The viaduct, one of the longest and highest in Portugal, is part of the Transmontana Highway, which will link the city of Oporto to the Spanish border when it is completed this October.
The Corgo Viaduct, with a length of 2,795 meters (9,170 ft), a height from the bottom of the valley of 230 meters (754 ft), and a main span of 300 meters (984 ft), will run over three roads and one railway line. Pillars number 18 and 19, the highest of the whole structure, are being built by two Linden Comansa Flat-Top tower cranes, model 21 LC 400, with maximum load capacity of 18 tons (39,680 lbs), and erected with jib lengths of 70 meters (229 ft), allowing them to load up to 5,000 kilos (11,020 lbs) at the jib-end.
The cranes are currently erected with a height under hook of 168 meters (551 ft), but both of them will soon reach a height of 207 meters (679 ft). The jacking-up of the cranes from the initial height (69.2 m / 227 ft) has been performed using a hydraulic cage J4-1 in three phases (up to 101m, 132m and 168m / 331, 433 and 551 ft) and, in a few weeks, the last jacking-up will be carried out to reach its final height of 207 meters (679 ft).
In order to ensure the stability of the cranes at such height, each one holds four ties to the pillar, at heights of 50, 81, 113 and 156 meters respectively (154, 266, 370, and 511 ft), and with a length from the crane’s mast to the viaduct’s pillar of up to 10 meters (32 ft).