Arch bridges

In the traditional form, a steel arch has a similar structural action to old masonry arch bridges. The arch springs from the foundations and exerts horizontal thrusts on them. The arch elements act primarily in compression. The deck may either be supported on struts, resting on arch below, or it may be suspended on hangers from the arch above.

A tied arch or "bow string" arch is a particular development of the arch form. The horizontal thrusts from the arching action are resisted by tension members between the arch springings. Effectively the deck acts as a tension tie, and is supported by hangers from the arch above.

This form is suited to the soft soils of riverbanks, where the ground cannot withstand the large horizontal thrusts from arching action.

Steel arches in one form or another have been used for spans ranging from 30m to 500m.

Example

Halfpenny bridge is a typical example of a graceful ‘bow-string’ arch footbridge. The bridge was completed in 2001, and carries a tow-path/ cycleway over the River Don, where it joins the Tinsley Canal near Sheffield (shown right).

Two further examples of arch bridges are the Hulme arch bridge, Manchester and the York Millenium footbridge (shown right).