Infinity Bridge

Infinity Bridge
Infinity Bridge from the River Tees Watersports Centre
Official name	Infinity Bridge
Carries	Pedestrians and cyclists
Crosses	River Tees, Teesdale Way
Locale	Stockton-on-Tees, England, United Kingdom
Designer	Expedition Engineering / Spence Associates
Design	Asymmetric double tied-arch and suspended deck
Material	Weathering steel, stainless steel and reinforced concrete
Piers in water	1
Total length	272 metres (892 ft)
Width	4 metres (13 ft)
Height	40 metres (131 ft)
Longest span	120 metres (394 ft)
Number of spans	10
AADT	4,000 people/day anticipated
Beginning date of construction	June 2007
Completion date	December 2008
Opened	14 May 2009
Coordinates	54°33′53.26″N 1°17′57.09″W / 54.5647944°N 1.2991917°W / 54.5647944; -1.2991917

The Infinity Bridge is a public pedestrian and cycle footbridge across the River Tees in the borough of Stockton-on-Tees in the north east of England. The bridge links, on the south bank the Teesdale Business Park and the University of Durham's Queen's Campus in Thornaby-on-Tees and on the north bank, Tees Valley Regeneration's £320m North Shore development area of Stockton-on-Tees.^{[1][2][3][4][5][6][7][8]} Built at a cost of £15m^{[5][6][7][8][9][10][11][12][13]} with funding from Stockton Borough Council, English Partnerships and its successor body the Homes and Communities Agency, One NorthEast, and the European Regional Development Fund^[3][6][14] the bridge is a major part of the North Shore Redevelopment Project undertaken by Tees Valley Regeneration.

The bridge had the working title North Shore Footbridge before being given its official name Infinity Bridge, chosen by a panel made from the funding bodies, using names suggested by the public.^[15][16][17]

Design

Initial investigations for the footbridge were done by the White Young Green Group^[5] who with English Partnerships produced a brief for an international design competition organised with the RIBA.^[5][8][18]

The successful competition design was by Expedition Engineering and Spence Associates.^{[citation needed]}

The subsequent design was led by Expedition assisted by Arup Materials, Balfour Beatty Regional Civil Engineering, Black & Veatch, Bridon, Cambridge University, Cleveland Bridge UK, Dorman Long Technology, Flint & Neill, Formfab, GCG, GERB, Imperial College, RWDI, Spence Associates, Speirs & Major, Stainton and William Cooke. White Young Green were Project Managers.^{[citation needed]}

The bridge is a dual, tied arch bridge^[19] or bowstring bridge. It has a pair of continuous, differently-sized structural steel arches with suspended precast concrete decking^{[2][6][7][8][9][11][12][18][20]} and one asymmetrically placed river pier. The offset intermediate river pier is to accommodate watersports and leisure craft to one side.^[21] No other bridge is known to have quite the same design.^[8][12] Supporting the four grey steel legs of the intermediate pier are four 3 m columns appearing just above the waterline, sat on a 2.5 m concrete slab supported by twelve tubular steel piles driven into rock in the river bed.^[21][22]

The information board on the bridge states the decking is 272 m long while other sources differ slightly at 273 m.^[19][23] The bridge walkway is 4 m wide between its stainless steel handrails.^[19][24] The main arch of the bridge is 120 m long, weighing 300 tonnes, 32 m tall with its top 40 m above the Tees.^{[7][8][9][10][11][13][17][18][19][20][25][26]} The short arch is 60 m long and 16 m tall.^{[9][11][13][17][18][19]} . Four exposed, high strength post tensioned cables run alongside the deck and tie the bases of the arches together. To ensure any bridge oscillation is controlled the bridge is fitted with seven tuned mass dampers - one on the short arch and six on the larger.^[18]. The mass dampers control horizontal as well as vertical oscillations - a feature only required on very slender bridges.

Illumination

A special feature is made of the way the bridge is lit at night. This lighting scheme was designed by Speirs and Major Associates^[1][18] who also designed the lighting for the Burj Al-Arab. At night the bridge handrail and footway are lit with blue and white LEDs. Uniquely it is believed for a bridge, these lights are designed to change colour as users cross. Attached to the steel cable ties are white up-lighters that illuminate the bridge arches, and blue down-lighters to illuminate the water and ground immediately below the deck. At night from certain viewing angles when the river surface is flat calm, the twin arches together with their reflection in the river appear as an infinity symbol ∞, and it is this effect that inspired its name.

Construction

The bridge was constructed in 18 months between June 2007 and December 2008.^[24] by site constructor Balfour Beatty Regional Civil Engineering and steel fabricator Cleveland Bridge & Engineering Company with White Young Green managing the whole project.^[20]

At the start of construction a temporary jetty was built on the south bank to enable the building of a cofferdam for the safe construction of the central pier.^[22] In April 2008 the supporting legs were added to the central pier.^[27] The first steel arch was put in place in June 2008^[7] and was used to stabilise the cantilevering lower portions of the main arch. On September 5, 2008 the large steel arch weighing 170 tonnes was lifted into place by a 1,500 tonne mobile crane, the largest in the country.^[7][11][28] The concrete deck panels were cast on site under a tent on the north bank of the river. Using a short temporary jetty on the north bank the deck panels were floated out on a small barge and jacked into position.^[11][29]

The footbridge was completed on time and to budget in December 2008 with 530 workers and uses in total some 450 tonnes of Corus steel,^[8] 1.5 km of steel cable, 780 lights, 5,472 bolts^[13] and weighs 1040 tons.

Operation

The bridge was officially opened on the 14th of May 2009 with celebrations organised by Durham-based She's Gott It^[2] and open to the public two days later on Saturday the 16th.^[30][31] It is expected that some four thousand people a day will use the footbridge^[8][11][12] and this is anticipated to rise as the University develops on the north bank.

Awards

The bridge won the Institution of Structural Engineers' Supreme Award for Structural Excellence 2009^[32], the premier structural engineering award in the UK.

The bridge was nominated for several awards but has not been without its controversy.^[33] The other awards the bridge has won include the Green Apple Award for the environment, the ICE Robert Stephenson Award 2009 and the North East Constructing Excellence Awards 'Project of the Year'.^{[17][25][26][30][31][34][35]}

Photo gallery

The smaller south arch	The large north arch	Central pier and large arch	The central pier
The first south pier viewed from the north side	The first south pier and concrete decking	The seven south piers and approach ramp	The north pier
The deck supports, support cable and bowstring cables	Bowstring cable tensioning clamps on the north bank	Infinity Bridge information board

See also

• River Tees
• Teesdale Way
• Teesdale Business Park
• Portrack
• Stockton-on-Tees
• Thornaby on Tees
• Tees Valley
• New Wear Bridge

References

External links

Wikimedia Commons has media related to: Infinity Bridge

• North Shore Footbridge website and duplicate North Shore Fans website
• Infinity Bridge in the Structurae database
• Infinity Bridge on 'Bridges on the Tyne' website
• Engineering design critique in The Happy Pontilist Blog
• Construction videos: BBC, Construction News, Building, Daily Motion, Google video, YouTube, Evening Gazzette
• Photographs: Flickr, North Shore Stockton, She's Gott It, Building, Queen's Campus, BBC Tees, Pbase
• Infinity Bridge on YouTube.