Der Bau eiserner Brücken im Südwesten Deutschlands 1844 bis 1889 - Gitterträgerbrücken und Taktschiebeverfahren (Teil 2)

Early iron bridges of south-western Germany 1844 to 1889 - Lattice bridges and incremental launching method (Part 2).

Since the time of the first iron Bridge at Coalbrookdale until the 19th century 'iron' was understood as 'cast-iron', because almost all early iron bridges were made of this brittle material. Based on this engineers designed intuetively correct compression loaded arch-structures, which had enough load bearing capacity for road-bridges, however which were not suitable for highly loaded railway-bridges with mobile loadings causing dynamical effects. For railway bridges the much more sustainable wrought iron had to be applied and other structural systems had to be developed.
The Britannia and the Conway Bridges on the railway between Chester and Holyhead in Northern Wales, designed by Robert Stevenson (1850-1894) in 1850 were of the first huge tubular beams made from large wrought iron plates, a milestone in engineering of that time. A few years later in 1857 a similar tubular bridge structure was finshed, the Weichsel-Brücke in Dirschau (nowadays Poland), where the iron plates were replaced by lattice girders constructed from crosswise arranged wrought iron ribbons according to the lattice girders invented by the American engineer Ithiel Town (1784-1844). Despite of various technical and statical problems of this construction the lattice-girders had important advantages concerning manufaction as well as the construction of multi-span beams designed this way.