Jackfield Bridge

Corus Construction Centre Jackfield bridge Bridged in steel Site history Facts and figures Site history Some 8km south of Telford, the fast flowing waters of the River Severn pass through the picturesque Ironbridge Gorge and beneath the famous 18th Jackfield Bridge Century Iron Bridge itself. The area is designated Client: Steel tonnage: as a World Heritage Site. Shropshire County Council 190 tonnes Designer: Steel quality: Gifford and Partners BS EN 10 025-grade FE 510D Iron Bridge view of the fact that it was toll-free. identified and a survey in 1985 Architect: Surface treatment: This illustrious structure, the first The load testing of the structure revealed that the bridge had Percy Thomas Partnership Blast clean to 1st quality bridge to be constructed of Iron, was carried out by a 14 ton steam become seriously under strength to Main Contractor: Aluminium metal spray 100µ was built as a toll bridge by Thomas roller. cope with even the lightest modern Alfred McAlpine Construction Ltd. 1st Coat Aluminium epoxy sealer Pritchard and Abraham Darby III in car traffic. Steel Sub-Contractor: 2nd Coat 2. Pack high build epoxy MIO, 125µ 1779, to serve the extensive The bridge itself earned recognition Westbury Tubular Structures 3rd Coat Recoatable polyurethane finish 50µ industrial development on both as an important structure and was In the interest of public safety a 3 Fabrication commenced: 4th Coat 2. Pack polyurethane finish 50µ, sides of the valley. It influences the eventually designated a Grade II ton limit was imposed in April 1986, October 1993 colour - metallic silver surrounding area through its listed structure of architectural and with traffic being restricted to a Fabrication completed: Design load: designation as a scheduled Ancient historic interest in 1985. The narrow single lane, controlled by traffic June 1994 Full HA loading - Special environmental Monument and consequently single carriageway three span open signals. Bridge open to traffic: weight limit of 17T imposed attracts large numbers of visitors spandrel arch had a central span of August 1994 Design Code: throughout the year. It is recognised 80 feet and side spans of 56 feet. It A structural assessment carried out Official opening: BS5400 as the forerunner to all modern steel was an early example of reinforced in the same year concluded that the 18th October 1994 bridges, although it used techniques concrete, designed by L G Mouchel bridge was beyond repair to carry more akin to a wooden structure. and Partners and constructed in six vehicles. The County Council months by the Liverpool immediately erected a temporary New Free Bridge Hennebique Company. steel bridge to relieve the old bridge In the early 1900’s the local Mayor, of all traffic loading. Councillor Maddox, raised funds to Decaying concrete and rusting steel build a toll-free alternative over the reinforcement was first noticed on Severn at Jackfield as a rival to the the structure in 1937 and heralded a famous Iron Bridge, then 130 years programme of extensive repairs old. throughout the next 50 years initially mainly due to carbonation of the In 1909, the alternative was erected concrete and latterly also due to less than one kilometre downstream chloride attack from de-icing salts. of the Iron Bridge at a cost of £1600 A 12 ton weight limit was imposed and was opened to traffic on 26 upon the structure, reducing to 10 June of that year. It was of tons in 1969 following major repairs reinforced concrete construction to one of the spandrel columns. and known as the Free Bridge in Further decay and damage was 2 Jackfield Bridge Jackfield Bridge 3 Conception Conception Site constraints on bridge The River Severn is also notoriously However, other structures on the form and design prone to flooding and combined site also hold significant roles, Practical considerations helped with the turbulent nature of flow, namely the old Free Bridge at dictate the choice of structure, with imposed two constraints upon the Jackfield which used the then newly visual implications also being of design which greatly influenced the discovered reinforced concrete great importance considering the choice of structure. No technique, the delicate tracery of sensitive location of the structure. intermediate piers were to be cast iron at Coalport Bridge erected within the water and the replaced a timber structure lost in The sides of the Severn Gorge are deck was to be positioned well the 1795 flood and the medieval unstable due to the cutting action of above flood level. A solution to the stone bridge at Buildwas which was the river creating oversteep side flood level was complicated further also lost in the same flood and slopes and evidence can be seen of by the requirement that the low replaced by a cast iron bridge landslips and damage to buildings levels of the approach roads were to designed by Telford. caused by subsidence. The Iron be retained. A structure was Conception of Jackfield Bridge Bridge itself has a history of therefore required that had its feet It was considered that the remedial measures and repairs out of the water, except in extreme innovative tradition of bridge Gifford and Partners were commissioned in July throughout its life, the most recent flood conditions, had minimum deck building in the gorge should be 1986 to carry out a study into the provision of a being the installation of a strut depth and could be erected from continued and that the vigorous, under the river in 1974 to prevent the embankments. challenging approach of the original replacement bridge. the lateral movements pushing the iron masters be matched. abutments together. Another practical consideration was Additionally, it was agreed that the that materials should be delivered to new bridge should provide a striking The old Free Bridge was in one of site in small sections as the narrow counterpoint to the older gorge The brief recognised the unique vehicles involved a detour of 14 too close to the Iron Bridge, mainly the more stable parts of the Gorge, winding roads, such a notable architecture. location and demanded a bridge of miles. After much consultation, the because it was judged that the sight but nevertheless ground treatment feature of the gorge, would prevent special quality and required wide construction of a new structure was and sound of traffic crossing the was decided upon prior to large sections being moved. The combination of considerable consultation to establish the proposed between Iron Bridge and new bridge would damage the commencement of the new practical implications and strong preferred type and form the Jackfield, some 400m downstream setting of the Historic Monument. structure. Injection grouting of coal The status of the surrounding area visual requirements made it clear structure should take.Particular of the former. seams in the underlying strata was influenced the final decision. that a high quality design was attention was to be given to the The pressing need for a new bridge carried out to fill any voids and Residing within the gorge is an required. question as to whether it should be The design put forward met the was recognised and following fissures which might influence local interesting sequence of bridges. a bold and visually striking practical requirements of the discussions with the Royal Fine Art stability and construction of the The most impressive being the Iron structure, or an unimposing and crossing, including the easing of Commission and English Heritage, bored pile foundations. Bridge with its pioneering status. purely functional one. access from the approach roads by the Secretary of State in 1993 eliminating a notorious hairpin bend granted listed building consent for Location on the south side. The existing the demolition of the old Free Traffic movements from Broseley to concrete bridge would have been Bridge and for a new structure to be Telford relied heavily on the old Free retained and converted into a built on the site of the old bridge. Bridge, and with increasing tourism pedestrian crossing following With the location of the proposed due to the growing popularity of the restoration. However in 1990, structure agreed, attention was World Heritage Site it was therefore following a Public Inquiry, the switched to selecting the right type essential that a replacement bridge Secretary of State for the of crossing to suit the environment. be built close to the existing one as Environment rejected the proposal the only alternative route for heavy on the grounds that it was felt to be 4 Jackfield Bridge Jackfield Bridge 5 Design solution Design solution Design solution In order to comply with the strict requirements and limiting constraints previously described, the proposed solution took the form of an asymmetrical cable stayed structure with a slender deck supported by a single pylon with its base out of the water. It was accepted that this solution section of circular form. The tower longitudinal compression and corrosion protection led to the was the most practical and elegant supports the deck via 8 locked coil bending, such that the deck slab tubes being filled with concrete to to relate with the environment of the rope cables of 96mm diameter, with could be at the same level as the form composite members. gorge. a further 8 cables anchoring it to the beam top flange. The concrete deck abutment. slab was designed simply to span The tower leg cross-member is The bridge has a single overall span longitudinally between the required to resist lateral forces and of 57.6m which is supported Design parameters were agreed at transverse steel cross girders. This in-plan twisting due to eccentric intermediately by the cable stays. an early stage, since they would arrangement allowed the deck loading on the deck.

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