The Saint-Nazaire Bridge - Saint Brevin France

Abstract

As a consequence of the industrial and tourist development of the region, it was necessary to construct a bridge across the Loire taking into account conditions such as the geological nature of the Loire river bed, the passing of up to 200,000 t oil tankers and other factors which were of utmost importance for the design and the subsequent construction. The work consist of two access viaducts and the central metal bridge. The viaduct, the outlines of which are curved in mutually opposite senses, are of prestressed concrete. They are made up equal spans, each of which has a length of 50.70 m between the pile axes, with in all 22 on the north side and 30 on the south side. Each span consists of: 4 prefabricated girders which are joined at the ends by tie members; between the girders there is a 0.50 cm thick fill layer, over which there is a reinforced concrete slab. The supporting piers, also of reinforced concrete, have a foundation of piles which generally speaking rest on the rocky substratum of the riverbed. The metal part rests upon two main piers, situated on either side, with same type of foundation as mentioned above. On these are located inverted V-shape pylons, with a short vertical element, to which the cables that support the centre bridge deck are anchored, formed by 96 m and 16 m long spans, welded together after having been lifted to their final level. This project —the greatest in France and the one that has the greatest clear span among the works of this kind— has required three years of work utilizing the most modern techniques and systems. More than 80,000 m² of concrete and more than 17,000 t of different kinds of steel have been used.