Whitby Bird & Partners
Peterborough Environment City Trust
The Shanks Millennium Bridge forms part of the Peterborough Environment City Trust Project funded by the Millennium Commission. It provides a new equine/pedestrian footbridge across the River Nene, and is sited at an ancient forded crossing. Following the construction of nearby sluice gates, the river became non tidal and the forded crossing impassable. The Shanks Millennium Bridge recreates a crossing at this location and links the north and south banks of the River Nene.
The structure is located 2.5km from the eastern edge of Peterborough. At this point the River Nene is contained by raised flood defence embankments, known as the North and South banks, and is above the general level of the surrounding drained farmland. It is open to a range of river traffic and contains a designated navigation channel.
The architect-designed bridge comprises a five span structure, approximately 120m long. It consists of a curved, slender steel box section, to which is bolted a cantilever walkway and handrail. The northern half of the bridge turns through approximately 90° in plan. The bridge deck comprises segregated footpath and bridle path areas at two levels. The footpath at the higher level is surfaced with hardwood. The lower bridge path deck consists of non-structural reinforced concrete. The parapets were constructed using a steel frame with hardwood slats set into the frame. This gives the horse and rider more space and, should any horses be startled, will prevent them climbing the parapet.
The shaped deck and the intermediate piers were constructed from weathering steel to reduce whole life maintenance costs and provide an architectural feature. Concrete abutments tie the bridge into the existing ground levels at the north and south ends. Two abutments were constructed on either bank of the River, and two intermediate piers located on the flood meadows.
Close working relationships that developed between all parties involved permitted drawings to be completed and approved in sufficient time to allow fabrication of the structure to proceed with minimal delay. The use of CAD/CAM provided a 3-D model, which gave virtual views of the bridge at every elevation and linked directly into automated fabrication facilities, including plate profiling and plate marking for assembly, minimising cost. The complex structure meant that all the steelwork was hand welded either in the steelwork contractor’s workshop or on site. The weathering steel was blasted at the works during the fabrication process prior to delivery to site.
Due to the complexity of the geometry, partial trial erection of box joints of the box sections was carried out at the steelwork contractor’s works.
The five span box girder sections were delivered to site in 12 individual box lengths. Each box section was supported by trestle towers and butt welded in the air to the adjacent box section. A crane was positioned on the flood plane adjacent to the River to enable the three box girders above the River to be erected. Closure of the River Nene was required during erection. Ancillary steelwork was then fixed to the bridge and then the decking and surfacing was added.
The complex design and the use of weathering steel has resulted in a bridge which is simple in its purpose to accommodate bridle path users and pedestrians whilst remaining aesthetically pleasing and architecturally challenging.
This is a most beautifully designed curved box girder bridge in weathering steel that fits the Fens landscape as if it were a natural part of it. It is a pity that land restrictions necessitated stepping of the decking on the approach to the south bank.