Guadiana Bridge conduits Spain and Portugal
One of the longest in the Iberian Peninsula, Guadiana flows 483 mi (778 km) through south-central Spain and southeastern Portugal, forming parts of the countries' borders, to the Gulf of Cádiz. Its headwaters rise in the mountains of Spain's Cuenca province; west of Daimiel they form marshy lakes, known as Ojos del Guadiana ("Eyes of the Guadiana"), a noted wildfowl sanctuary. In 1991, the Guadiana International Bridge (Spanish: Puente Internacional; Portuguese: Ponte Internacional) was built that crosses the Guadiana River connecting southern Spain (town of Ayamonte) and Portugal (town of Castro Marim). It is not split evenly between the two countries, with a greater share of it situated in Portugal. This bridge is a cable-stayed bridge, with a deck of prestressed concrete. The bridge is open to vehicles only.It is one more of the longest bridges of Spain and third longer bridge of Portugal after Basque Bridge of Range and Bridge 25 of April, both in Lisbon.
The idea to construct a highway bridge that united both shores of the Guadiana in its opening dates from very old, but it was not until years 60 of 20TH century, when the Governments of Spain and Portugal were agreed to initiate the studies of viability of the work. These began in 1963 and finalized in 1985 with the company/signature of an agreement between Spanish Main directorate of Highways and Together Independent of Portuguese Estradas . The project was the responsibility of Portuguese engineer Jose Luis Cancio Martins and the works were realized by the Spanish Huarte S. the Portuguese Teixeira Duarte.
The bridge is a part of the road link between Spain and Portugal, close to the Spanish town of Ayamonte (Huelva) and the Portuguese town of Castro Marim (the Algarve). With a four years of construction, it has a total length of 666 m between the abutments, is 18 m wide and 20 m above sea level at its centre point. The bridge is divided into five continuous spans, with a combined length of 594 m, long, are suspended by 64 pairs of cables. The two main towers, raised as an "A" and nearly 100 m high, have an opening at the foot of 30 m between the axes. The tower on the Spanish side is built on an artificial island in the river bed, and its equivalent tower on the Portuguese side, as well as two minor pillars, is built on-shore.
The towers are hollow and the inside can be seen along their entire height; the cables are anchored in a single shaft at the top. The bridge deck has four traffic lanes and parallel service sidewalks, where the cable anchors are located. The deck cross-section consists of a tray 2.5 m deep, stiffened inside along the anchored spans by triangulated diagonal sections. To assess the current state of the bridge and prepare the installation of a continuous monitoring system, an ambient vibration test was performed. This bridge was selected because of the frequently observed high amplitude oscillations of its staycables under winds of moderate speed. These observations have already led to studies on the vulnerability of the cables to parametric excitation.
The main difficulties with which the engineer ran into were the width of the Guadiana to that height, who is of almost half kilometer, and the depth of the river, of about 10 meters. During almost four years 300 people worked in the bridge who moved 28,000 cubic meters of concrete, 5,500 tons of steel and 2,100 meters of piles of two meters of diameter. The Bridge the International of the Guadiana counted, at the time of its inauguration, with the second central major vain in concrete bridges.
The construction process began with the towers. Once they were raised and the starter segments were constructed, the deck was constructed using successive overhangs, with formwork carriages at each tower. Work was carried out on the four fronts at the same time (two per tower), supporting each successive overhang with the cables. Significant technical innovations were applied to the works. The cables used a novel solution that resolved the problem of cracks and corrosion suffered by conventional cables, by removing the cement-grout injection. Furthermore, techniques were used for loading purposes, reducing the usual complications inherent to traditional systems, thanks to a comprehensive analysis of the mass-stress/length ratio. Finally, the entire assembly process was strictly supervised by the works team, using a complex computer program for this purpose.
EOM
Source: From 'Multi-run Operational Modal Analysis of the Guadiana cable-stayed bridge' by Bart Peeter, Filip Dammekens, Filipe Magalhaes, Herman Van der Auweraer, Elsa Caetano, Alvaro Cunha