Crown Point Bridge (Leeds)
Crosses the River Aire in Leeds, Yorkshire
See also Happy Pontist website.
Built in 1842 as a cast iron arch bridge, designed by George Leather and John Wignall Leather (Leather and Son).
The ironwork was produced by Booth and Co of Park Iron Works, Sheffield. Bray and Duckett undertook the masonry work.
Original span 120 ft, and width between parapets was 42 ft.
The bridge was built a short distance above Nether Mills Weir. On the south bank, part of Chadwick's dye house was demolished to accommodate the bridge. Medley's oil mill was on the north side.[1]
At some point the eastern aspect of the bridge was spoiled by the attachment of a pipe bridge for a water main, with consequential damage to the ironwork and to the masonry abutments. Further damage was done when the main was renewed in 1979. Subsequently it was decided to widen and upgrade the bridge to accommodate 40 tonne vehicles, and the opportunity was taken to restore the appearance of the eastern (downstream) face. The laudable and impressive project was undertaken in 1994-5. The outermost pairs of cast iron arches were retained, while steel arch ribs were installed to provide the main structure. The treatment at the eastern end was particularly impressive, particulary because of a requirement to accommodate a gradual widening of the river, which involved progressively increasing the span of the last three steel ribs and retaining the outer pair of cast iron arch ribs at the eastern end, while increasing their span. Here the span was increased by 5m to 41.6m (136 ft), requiring new abutments. In order to increase the span of the two segmental cast iron arch ribs on the downstream side, a 7.5m section was removed at the crown, and replaced by a 12.5m section. The new section was assembled from three castings. This approach was possible because, as designed, the ribs are assembled from segments connected together with abutting flanges. The radius of the new segments was specified to give smooth curvature. The arch springing here increased by 0.42m (16.5"). The main contractor was Birse Construction. The steelwork contractor was Fairfield-Mabey. The ironwork was subcontracted to Marsh Brothers of Bakewell, who subcontracted production of the rib segment castings to Lloyds (Burton).[2]. The Leeds City Council's Chief Bridge Engineer was Richard Kay, M.I.C.E., and the Resident Engineer was Stuart Rothwell, M.I.C.E.
Referring to Fig 2, the 'flared' increase in span at the downstream end of the bridge is indicated by the angularity of some of the transverse plates between the last four steel ribs.
Cast Iron Structure
As indicated in the photographs, the foundrywork is of a very high standard, with fine moulding and a high standard of fitting. Presumably the original joint faces were machined by planing.
The outermost arch ribs are ornamented, and the segments are joined using cotters, while the rest of the rib segments are I-beams of plain appearance, with robust bolted flange joints. Both types of connection can be seen in Fig 7. The segments of the inner cast iron ribs do not butt directly together - a cast iron frame being sandwiched between each pair of flanges. The situation for the outermost ribs is more complicated. For structural reasons, the frame is clamped between the flanges, but for reasons of appearance it was desired that the edge of the plate should not be visible on the outer face of the rib, and to the outer ends of the segments would butt directly against each other, and the joint should be practically invisible. Fig 7a shows that this has been largely achieved.
The ends of the arch ribs are rounded (Fig 8), and sit in corresponding bearings, with the intention of allowing the ribs to rise and fall with temperature changes. This arrangement was also used on some of George Leather's earlier iron bridges.