Where simple arched bridges are used for railways on flat terrain the cost of building long approach embankments may be considerable.Flattening the arch shape to avoid the humpback problem, such as for Brunel's Maidenhead bridge, increases this side thrust.As well as tying the side-loads of the arch, the tension member is also at a convenient height to form the bridge deck, as for a through-arch.Although visually similar, tied- and untied- through-arch bridges are quite distinct structurally and are unrelated in how they distribute their loads.In some cases, this type of arch has been created by constructing cantilevers from each side, with the shoreside ends bolted securely down into heavy piers.This type of construction was used in the Sydney Harbour Bridge illustrated above, with the supporting cables to the higher side of the arches removed after completion.
The
Frederick Douglass Memorial Bridge
under construction in 2020. The partially completed arch is supported by wires attaching it to the completed arch behind it.