RRC promotes a technical visit to its Corgo viaduct site
The special characteristics and different construction methods adopted for the Corgo viaduct, which is part of the Transmontana motorway concession, are such that interest was so high among technicians that RCC organised a visit. The visit, organised as part of a plan of technical visits developed and promoted by the construction division, was not only for engineering technicians and architects but also safety and environmental technicians. The joint venture responsible for all the construction work includes Ramalho Rosa Cobetar and FCC Construcción, among other firms.
It is a pre-tensioned reinforced-concrete viaduct with a total length of 2,796 m, divided into three successive sub-viaducts — the western, central and eastern sections, which are 855, 768 and 1167 m long, respectively — between the axes of the end supports.
In the area of greatest difference in level with respect to the ground, the deck is fixed nearly 230 m from the bottom of the valley, having opted in this central area, after detailed analysis of the local terrain and any feasible areas for locating the piers, to build the deck with a 300 m main span over the river Corgo valley, with two adjacent 126 m spans, using a cable-stayed solution with a central suspension system, prolonged by continuity spans on each side, to obtain a total length of 768 m for the central sub-viaduct, distributed (from P15 to P22) as follows: 48.0+ 60.0+ 126.0+ 300.0+ 126.0+ 60.0+ 48.0 m.
The eastern and western viaducts, which are structurally continuous, are composed of standard 60 m spans. According to this, the deck takes the form of a central caisson 3.5 m high, with 0.60 m cores positioned every 9.40 m between the axes and with the side wings resting on regularly laid-out props 3.0 m apart. The central sub-viaduct features central suspension of the deck with stays positioned every 6.0 m, with masts and the corresponding monolith-type piers on the deck. The first stays were fitted at a distance of 21 m from the axes of the piers.
The set of four panels each with 22 stays, which makes up the staying system for the central sub-viaduct, varies between 39 and 73 15.7 mm pre-tensioning ropes, with a minimum length of nearly 38 m and a maximum length of around 159 m. This is symmetrical cable-staying in relation to the masts, which is where the diversion benches are to be fitted. Suspension of the deck via the stays (exterior), fitted every 6 metros in a half-fan layout, is feasible thanks to the internal suspension of the caisson-beam cores, using pairs of structural steel stays, and thanks to the stress-transfer model adopted.