Eight stages to a landmark bridge

1 Design competition
In 1997, civil engineer Gifford and Partners and architect Wilkinson Eyre Architects won a design competition for a new pedestrian bridge sponsored by Gateshead council.

"A contemporary design which complements the existing Tyne bridges in a way that is both refreshing and new," commented the judging panel. Although they had not worked together before, both firms had award-winning track records in bridge design.

2 Contract
Local civil and marine engineer Harbour & General was awarded a £13.7m construction contract by Gateshead council. "We were able to show that we had all resources on tap," says project manager Steve Aspinall. An ICE New Engineering Contract was adopted, with a partnering project management team made up of representatives from client, engineer, architect and even the contractor itself.

3 Abutment construction
Harbour & General constructed the concrete abutments alongside either embankment. Some 28 piles were sunk into the river-bed to a depth of 30 m. Reinforced concrete bases were then cast on the pile caps in thicknesses of up to 3.9 m.

4 Steel arch manufacture
The bridge arch and deck were fabricated as hollow box frames of 20 mm steel plate by Amec subsidiary Watson Steel in its Bolton plant. "The biggest challenge was that there were no straight lines in the steelwork," says Watson foreman Geoff Pilling.

5 Arch fabrication
Twenty-three steel box-framed sections up to 15 m in length were transported to Amec's offshore fabrication plant at Wallsend on the mouth of the River Tyne. Here they were assembled and welded together to form the arch and deck and temporarily braced with a spreader beam. Meanwhile, M&E contractor Kvaerner Markham fabricated the hydraulic equipment and cast-steel fixing brackets, incorporating high-tensile steel axles from Italy and ball bearings from Austria.

6 Alignment of bearings
"It is vital that there should be no racking or twisting between the two axles as the bridge opens," says Aspinall. "So our main problem was accurately aligning the two bearing plates to which the brackets housing the axles are bolted. We started by fixing one of the two bearing plates on one abutment. Then with EDMs [electronic distance measurement instruments] and a very competent site engineer we aligned the other three bearing plates on both embankments to it. The design tolerance was just +/–2.5 mm across a distance of 126 m. In the end, we achieved a tolerance of +/–1 mm."

7 Installation of double arch
The most dramatic operation was the installation of the double arch. The world's second largest inshore floating crane, which has a 120 m high jib, was hired from the Netherlands to transport the double arch six miles upstream from the fabrication yard to the site. Because of the narrowness of the river, the double arch, which weighed 1100 tonnes including lifting gear, was transported parallel to the banks, and was swung around by 90° at the site.

"The original plan was that the bridge would be dropped down within 50 mm of its final position and then be shunted by jacks," says Aspinall. "But it sat down more or less perfectly, and the whole operation was over by 9:30am. That gave us a tremendous feeling of relief and pride."

8 Final works and commissioning
Work is under way to fix the stainless steel balustrading to the pedestrian and cycle decks. Later, the hydraulic opening gear and software will be connected up and commissioned, and the two glass pavilions erected. As a separate contract, Gateshead council will landscape the contractor's compound as "Millennium Plaza". The bridge and plaza are due to open to the public in early September.