Old Iron Bridge, Merthyr Tydfil
[2] Although an important early example of iron bridge-building and well known as a local landmark within living memory,[3] the bridge has largely disappeared from engineering history.
[4] Cast iron was now established as a viable material for bridges and a number were produced in the years immediately afterwards.
[ii] Richard Crawshay's Cyfarthfa Ironworks was on the West bank of the River Taff, the opposite side from the centre of the developing town.
The abutments of the bridge were stone, battered back with sloping faces so that they met the ends of the arch panels perpendicularly.
[12] However the short life of the timber gave trouble twenty years later and the bridge required extensive repairs.
[12] There were three perpendicular uprights to each panel, with strips forming a pair of intertwined waves between them, giving an 'X' shape in each of the four spaces.
Three horizontal strips of wrought iron were riveted to the back, to make the gaps in the balustrade smaller,[1] and these appear to have been added later.
Most of these were to the stonework of the bridge abutments or the stone retaining walls of the riverbank, particularly for improvements to reduce the effects of flooding.
William Williams, Watkin George's successor as chief engineer of the ironworks, made a report on its condition and recommended that an iron decking of flat plates should be applied over the existing structure, then a pavement of stone or iron treads be applied over that.
[13] It has been suggested that the cross girders directly beneath the surface of the bridge had been installed during the 1817 repairs, their cost explaining the large sum of paid for castings.
Roadbuilding and bridge projects could stimulate a local economy and trade, whilst also providing employment to the demobilised soldiers.
He went so far as to suggest that the bridge was both unsafe in its current state and that it was beyond economic repair, largely due to the need to dismantle it almost completely.
[20] By 1860, after a long delay, the Board of Health decided to seriously consider replacement and began with a traffic survey of the current bridge.
[21] A replacement bridge was long overdue; apart from the concerns over its structure, its narrowness and the amount of traffic using it led to accidents.
[24][vii] This required a longer bridge, and it was also widened to be more easily capable of carrying vehicle traffic.
The bridge remained in use until WWII, although as just a footbridge with bollards to prevent vehicles, after which the ends were fenced off, pending its demolition.
