Springfield Iron Bridge (Chelmsford)
No longer extant.
It was a very early example of an iron bowstring (tied-arch) iron bridge. It was very short-lived.
1820 ' The new cast iron Bridge, which divides the parishes of Chelmsford and Springfield, Essex, was opened for carriages of every description, on Friday last.'[1]
1820 'IRON BRIDGE OVER THE RIVER CHALMER.
This bridge, which does great credit to the architect, Mr. Dodd, was opened for the public on Friday the 15th of Sept. 1820. It crosses the Chalmer in the county of Essex at Springfield, in the great east road leading from Chelmsford to Colchester, Harwich, to the counties of Suffolk and Norfolk. It is a beautiful structure, and differs from all the iron bridges hitherto erected, by requiring no buttresses, but resting on iron columns or standards driven into the banks of the river, having no lateral pressure, but merely resting on its supports.
'The method adopted in the erection of this bridge holds out great promise of economy in future bridge building. No excavation required;. no coffer dams; but merely the iron columns driven as far into the earth as they could be by a pile engine: they were then made the fulcrum of a lever loaded with three times the 'calculated weight of the bridge. The bridge is also so constructed as to require no spandrils — thus leaving the same altitude for the passage of vessels under every part of the span.
'The principal strength and stability of this bridge is obtained by elliptical arcs and chords, kept so flat that the purposes of the truss girder are fully obtained, but with superior elegance and greater strength, and may be extended to an indefinite length.— Two of those cross the river, their extreme ends resting on the iron pillars driven in the river banks, and not projecting higher than the handrail of the balustrades_ with an extended chord from the two points of the basement, holding them altogether, and preventing their extending by pressure; to which elliptical arc-piece are attached or hung chords of suspension for supporting the bridge-flooring — these chords of suspension being flat, form stiles between pannels of tasteful Gothic work; the whole forming balustrades on each side the bridge. It being on the principles of tenacity, the chief part of the iron acts longitudinally by tension. There are grooves in the top of those iron columns, on which the whole bridge has room to contract or expand, so necessary in this climate from the various changes of the atmosphere from heat and cold, as the other previous iron bridges have suffered materially from the want of this precaution, and evidence has been given before the Parliament, that the Southwark bridge rises from 2 to 2 1/4 inches in the middle of the day, and settles again in the evening. By those iron columns in the river, instead of piers or buttresses, if they resist the floating ice, of which from their strength and stability there can be no doubt, Mr. Dodd, the engineer, has certainly introduced an economical plan in bridge-building, as in this there is no occasion for battre-d'eaux, coffer-dams, &c.; a saving most desirable in the expensive work of bridge building — particularly so, as they are executed with such facility, and without the expense of centering, and upon this principle can be built to any order, instead of the fillagree patterns hitherto adopted.'[2]
J. G. James[3] described it as a light wrought-iron bowstring bridge. The length was 32ft and the width 21 ft. 'The bridge proved to be hopelessly under-designed and soon needed propping. Maudslay and Donkin reported on the failure 16 February 1821 blaming it on the use of inadequately-sectioned bars in compression and weak connections.'