Some aspects of the development of the girder bridge 1820-1890

Abstract

The thesis explores very briefly the background history of bridge construction from Roman times, and the development of masonry arch bridges to suit the spreading network of roads, both in Britain and overseas. The need for the girder bridge made itself felt with the coming of the railways, and early examples in timber, mainly in America, soon gave way to iron. The girder and beam were mostly used on their own as bridging solutions, but also gave an impetus to suspension bridge design in their application as stiffening trusses. The bridge girders could not be effectively and safely used without appropriate calculation, and early efforts to solve this problem were devised by Louis Navier in France and Eaton Hodgkinson in England, on which some comment is made. It was not long before various types of girder began to emerge, often named after their inventors, or patentees. The thesis explores firstly the development of the girder bridge in Britain from 1820 to the 1860s, and then the corresponding development in America over the same period. The suspension bridge, the arch bridge and the tied arch are not included, as they are not strictly speaking, girder bridges. The girder bridge is typically a structure with near parallel flanges in which the load is shared between each, and there are web members joining the flanges to resist the shear loads. There are some bridges which appear to deny classification, but a little careful assessment will usually allow a distinction to be made, as in the case of Brunel's bridge at Saltash. The study continues up to the advent of cantilever bridges, and in particular the Forth Rail Bridge, completed in 1890. This bridge was described by its designers, not as a cantilever as it is commonly known nowadays; but as a "continuous girder bridge". After 1890, design principles and methods of calculation were well developed. Further innovation did not take place until more recent times, and it has been chosen to end the study at that date