COMBINING PRESTRESSED CONCRETE AND STEEL FOR BRIDGE CONSTRUCTION

Abstract

This paper describes methods other than computer aided fabrication for the design of prestressed concrete and steel composite bridges. It first describes the attempts carried out between 1982 and 1985 in France to develop a new design for composite cross sections wherein the classical webs of box girder were replaced by steel webs. Examples provided are: a) the La Ferte Saint Aubin bridge, where the concrete webs have been replaced by plane steel webs; b) the Arbois bridge over the River Cuisance in Jura, where two concrete webs have been replaced by 2 plane steel trusses; c) the Cognac Bridge, over the River Charente. Here the two concrete webs have been replaced by two folded steel webs which do not carry any longitudinal compression. Prestressing efficiency is therefore increased; and d) the Val de Maupre viaduct, near Charolles. Two folded steel webs are used in this box girder bridge, and the concrete bottom flange is replaced by a steel tube filled with concrete. New developments in prestressing classical composite structures are also presented briefly, as is the design method which distributes steel and concrete along the entire length in such a way as to take advantage of the differences in weight between the materials. In essence, the main span is built of lightweight concrete which is balanced by shorter side spans built in traditional concrete. Examples are provided of steel isotropic spans supported by concrete cantilevers, (for example the Queen Mathilde Bridge at Rouen), cable stayed bridges with a steel main span (for example the Chevire Bridge). The use of lightweight concrete for constructing the bridge deck of arch bridges is also described, and illustrated by the bridge over the River Rance. The French title of this article is: Les ponts mixtes associant l'acier et le beton precontraint. The German title of this article is: Vereinigung von Spannbeton und Stahl im Brueckenbau. For the covering abstract of the conference see IRRD 851274.