The Construction of Railway Bridges Then and Now

Abstract

Prior to 1900 the railways were mainly built by manual labour. Masonry arch, timber and cast-iron bridges were constructed piecemeal. Long spans over waterways were floated out on pontoons and raised using hydraulic presses. As bridges of timber and cast iron became unsuitable they were replaced by wrought iron and later by steel or concrete. Speed of construction was vital once railways came into use demanding that works were carried out in track possessions and this influenced construction methods thenceforth. Steam breakdown cranes appeared from 1875 and were soon being used in bridge construction. As crane capacities increased bridges were erected in larger elements. The adoption of welding to replace riveting and wider use of concrete in superstructures after 1945 was assisted by the introduction of road mobile cranes whose capacities reached 1000 tons by the 1990s. ‘Rolling-in’ of spans preassembled alongside the tracks was developed to reduce possession periods. From the 1980s Transporters were introduced to install complete spans, so eliminating temporary works. Substructures beneath live tracks had been traditionally constructed in cofferdams spanned by waybeams, but from the 1960s pipe-jacking techniques were adapted to form such substructures. Piled foundations on each side of the railway have increasingly been adopted and from the 1970s integral portal frame bridges or boxes have been installed by sliding-in, with transporters, by jacking or pulling in open cut.