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Portfolio > North East England 2 > Infinity Bridge, Stockton-on-Tees                                              Click on an image below to reveal enlarged version

Infinity Bridge, Stockton-on-Tees, UK

The Infinity Bridge is a public pedestrian and cycle footbridge across the River Tees in the borough of Stockton-on-Tees in northern England. The bridge is situated one kilometre downriver of Stockton town centre, between the Princess of Wales Bridge and the Tees Barrage. It connects the Teesdale Business Park and the University of Durham's Queen's Campus in Thornaby-on-Tees on the south bank of the Tees with the Tees Valley Regeneration's £320 million North Shore development on the north bank. Built at a cost of £15 million with funding from Stockton Borough Council, English Partnerships and its successor body the Homes and Communities AgencyOne NorthEast, and the European Regional Development Fund the bridge is a major part of the North Shore Redevelopment Project undertaken by Tees Valley Regeneration. The bridge had the project title North Shore Footbridge before being given its official name Infinity Bridge, chosen by a panel of representatives from the funding bodies, from a pool of names suggested by the public. The name derives from the infinity symbol, formed by the bridge and its reflection. 

 

The bridge is a dual, tied arch bridge or bowstring bridge. It has a pair of continuous, differently-sized structural steel arches with suspended precast concrete decking and one asymmetrically placed river pier. The tapering arches with a trapezoidal box section are fabricated from weathering steel plate. Each of the arches bifurcates within the spans to form a double rib over the river pier. A reflex piece between the two arches holds them together, making the two arches one continuous curve. No other bridge is known to have quite the same design. The offset river pier is to accommodate water sports and leisure craft to one side. The river pier is supported by an 11.5 m square by 2.5 m thick pile cap on sixteen 1 m diameter hollow steel pipe piles. On the pile cap beneath the water line are four 3 m cylindrical concrete legs, onto which are bolted and welded the four inclined grey steel legs visible above water. Riprap covers the river bed around the river pier for scour protection against the large flows when the Tees Barrage downstream discharges. Each of the two concrete riverside piers are supported on four 500 mm hollow steel piles and a pile cap. The bridge as initially proposed was to have been some 272 m long. It was originally designed with a northern approach 38 m long and a southern approach of 54 m, however, the design of the north side of the bridge was later simplified and the bridge's northern approach shortened. The design of the southern approach is largely unaltered and has a staircase connecting it directly to the river frontage. The bridge deck is 5 m wide and 4 m between its custom-made handrails. The main arch of the bridge is 120 m long, weighing 300 tonnes, and 32 m tall, with its top 40 m above the Tees. The short arch is 60 m long and 16 m tall. The hangers (droppers) are spaced 7.5 m apart and are made from 30 mm diameter, high-strength, locked-coil steel cable. Four exposed, high-strength, post-tensioned, locked-coil steel-tie cables run alongside the deck and tie the bases of the arches together, pre-stressing the concrete deck sections. The tie cables are 90 mm diameter on the large arch and 65 mm on the smaller.

The aggregate concrete deck sections are 7.5 m long and down to 125 mm thick in places, making it one of the thinnest bridge walking surfaces. The handrails and parapet are stainless steel, while the balustrade is made from stainless steel wire. To ensure any bridge oscillation is controlled, the deck is fitted to the underside with seven tuned mass dampers – one on the short arch, and six on the larger weighing 5 tonnes in all. The mass dampers control horizontal as well as vertical oscillations — a feature only required on very slender bridges. There is provision for the addition of further dampers when the issue of maintenance arises. The clearance (heading) below the decking on the navigable part of the river is 8 metres.

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[9] who also designed the lighting for the Burj Al-Arab. At night the bridge handrail and footway are lit with custom-made blue-and-white LED lighting built into the handrail that changes colour as pedestrians cross the bridge; sensors trigger a change from blue to white, leaving a 'comet’s trail' in the person's wake. Attached to the steel cable ties are white metal-halide up-lighters to illuminate the white painted bridge arches, and blue LED down-lighters to illuminate the water and ground surfaces 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.

 

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