Prefabrication of concrete box girder bridges

The technologies described in this paper allow the construction of prestressed concrete bridges, precast in a monolithic form both for simply supported and continuous beams. It combines durability, speed of construction and economy. Particular reference is made to construction of a viaduct with a continuous box girder deck under construction in a seismic zone in Italy. (The Poggio Iberna viaduct). This system of construction is as follows. Each box girder span is precast with 8 hours continuous pouring of concrete and prestressed using the pretensioning system. It is then lifted using hydraulic jacks and placed on transport consisting of 16 railway trolleys. Each trolley is fitted with a hollow rubber cylinder in order to distribute the weight of the element evenly. This trolley equipment carries the precast box along the completed part of the viaduct to the launching position where it can be lowered into place. Each launching phase takes about 2 hours. The entire cycle, from construction of the element to its setting in place, takes 24 hours, using the hours of darkness for the steam curing phase. (A) The French title for this article is: Prefabrication des ponts a poutre-caisson en beton. The German title for this article is: Vorfabrikation von Kastentraegerbruecken. For the covering abstract of the conference see IRRD 851274.