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Awards celebrate bridge with the past

ICE news

FOUR BRIDGES shared top honours and four more received commendations in the 2001 ICE Historic Bridge Awards.

Bridge conservation is 'very difficult to celebrate properly', said ICE president Mark Whitby presenting the awards last Thursday at the ICE.

'With old structures you have to look into the minds of the engineers involved, generations of them, ' he said. 'We take our turn to do our little bit.'

The competition is run to recognise and encourage excellence and innovation in the conservation of bridges more than 30 years old, and is sponsored by the Institiution of Civil Engineers in conjunction with Railtrack, English Heritage, CSS and British Waterways.

This year 15 entries were judged by a team led by chairman of the panel for historic engineering works, Professor Roland Paxton.

Winners

Project: Hammersmith Bridge Strengthening, London Client and engineer: London Borough of Hammersmith & Fulham Designer: Hyder Contractor: J Murphy The judges were highly impressed by the latest round of detailed and sympathetic repairs completed on Sir Joseph Bazalgette's 122m span suspension bridge over the Thames at Hammersmith.

Built between 1884 and 1887 on the piers of an earlier crossing, the latest strengthening works followed an assessment in 1996 which found the structure was not capable of carrying 7.5t vehicles because of apparent deficiencies in the tower bracing, suspension chains, stiffening truss, hangers and cantilever footway brackets.

Vertical loads were transferred to new hangers while plates were added to the top flanges of the stiffening trusses. In a delicate jacking operation, elastomeric bearings were inserted in the Hammersmith tower saddle to replace seized steel rollers from earlier repairs.

Commended

Project: Cookham Bridge Strengthening, Berkshire Client: Royal Borough of Windsor & Maidenhead Designer: Babtie Contractor: Mowlem Others: Dorothea Restorations 'Exceptional work' was involved with welding the wrought iron girders of Cookham Bridge, following extensive off site testing.

The overall result is that an attractive bridge has been sympathetically restored to its function as a 7.5t capacity structure combining roadway and a footway.

Project: Footbridge 35 restoration, Whitchurch, Shropshire Client: Railtrack Designer: Tony Gee & Partners Contractor: CLM Construction Others: Heritage Engineering;

Tividale Fabrications Extensive corrosion, rotten timber and vandalism meant extensive replacement not conservation of the attractive footbridge spanning the old London & North Western Railway at Whitchurch.

Project: Inclined Plane Bridge Strengthening, Coalport, Shropshire Client: Telford & Wrekin Council Designer: Babtie Contractor: Cintec Others: Gifford Invisible repair using 12 Cintec anchors has upgraded the 210 year old brick arch spanning the Hay Inclined Plane to carry 40t vehicles.

Project: Marton Bridge Restoration, Warwickshire Client: Highways Agency Designer: Warwickshire County Council Contractor: Mowlem Others: Wragg Brothers Marton is one of the oldest surviving bridges in England. Built as a masonry structure in 1414, it has been repaired and altered many times. But in 1926 the upstream side of the bridge was subsumed into a 20th century widening project. It has just been carefully detached from the widening and restored as a pedestrian structure while the A423 trunk road it part carried has been diverted over a new bridge running parallel.

Project: King Street Railway Bridge Strengthening, Mold, Flintshire Client: Flintshire County Council Designer: Tony Gee & Partners Contractor: Concrete Repairs Others: DML Devonport Composites The judges described this carbon fibre reinforcement of a cast iron former rail bridge as a 'very neat solution.'

Ugly trestles had been inserted under nearly half the span of the bridge, which carries King Street over a disused railway now forming the entrance to a car park. But even with these supports the bridge was only capable of carrying 17t loading, not the 40t required.

In a novel strengthening technique, the cast iron beam and brick arch infill deck was jacked up to allow tapered, high modulus, carbon fibre plates to be bonded to the beam soffits so that the reinforced deck structure acts compositely for both self weight and traffic loading.

Project: Mercury Bridge rebuilding, Richmond, North Yorkshire Client: North Yorkshire County Council Principal designer: Mouchel North Yorkshire Contractor: Morrison Construction Others: Pell Frischmann (foundation design); Butterly Engineering (temporary steelwork); Fondedile Piling (mini piling); Eslington Stone (masonry design and erection); Dunhouse Quarries (masonry supply) 'Getting temporary works under those arches was a wonderful feat of engineering, ' commented the judges. The daunting task completed after floods in June Project: Winston Bridge Strengthening, County Durham Client: Durham County Council Designer: Gifford & Partners Contractor: Cintec International Others: Rockfield Software; TRL Winston Bridge won its award through 'technically brilliant' engineering which meant no repair work was actually needed to upgrade its load capacity to 40t vehicles.

Previous, conventional, assessments had concluded that the limit should be 17t, and some £90,000 of reinforcement work with Cintec drilled anchors was set to be carried out.

However, more precise 2000 scoured away one of the piers of Mercury Bridge.

The decorative masonry bridge built in 1890 spans the Swale and is an important access to Richmond. North Yorkshire County Council looked rapidly for contractors to stabilise and rebuild the structure to forestall its total loss.

Temporary foundation caissons were placed in the river bed and used to support deep section steel beams forming two A-frame spans from which the precariously balanced masonry could be chocked.

New deep piled foundations were then installed from within temporary cofferdams and the masonry piers and arches reconstructed above.

analysis by the ELFEN software program determined that nothing needed to be done to the 32.3m arch.

'It meets our aims as near perfectly as possible, ' said the judges, who take their lead from English Heritage's basic conservation culture of: 'Do nothing to interfere with historic structures, wherever possible.'

Special mention

Project: Cleddau Bridge Pier Top strengthening Client: Pembrokeshire County Council Designer: Flint & Neill Contractor: Concrete Repairs Others: Tony Gee & Partners A Special Mention was given to Cleddau because, although it is less than 30 years and hence does not meet the competition's requirements as a historic bridge, the strengthening work on the six slender reinforced concrete piers was very neat and simple.

Drilling and reinforcement with high tensile bars and a subsequent wrapping of carbon fibre reinforced polymer involved minimal interference to an elegant structure.

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