A PRIDE OF BRIDGES ON PETERBOROUGH PARKWAY

Three bridges on the parkway, a dual carriageway road in Peterborough which was opened in December 1984, are described. Bishops bridge, built with spread footing foundations carrying raking stem abutments, has a deck formed of standard precast prestressed concrete inverted vee beams with solid in situ concrete infill. It has a single 15 m skew span. The Fletton bridge is a five-span in situ reinforced concrete continuous deck structure, designed as two bridges side by side but sharing the same abutments. Vertical stem abutments and piers cantilever from the piled foundations. The deck is of cellular construction to reduce weight, using expanded polystyrene void formers. Sliding bearings are provided at intermediate pier supports, with the bridge fixed at one abutment and provided with a movement joint at the other. The bridge over the Nene River is 154 m long and 23.20 m wide between parapets, carrying a dual carriageway, hardstrips and a cycleway/footpath. Curved in plan, the deck is skewed over the supports from zero to 14.5 degrees, with spans of 25.5 m, 25.5 m, 31 m, 40 m and 30 m, widths which in their variability were optimally suitable to the layout of river and ground, both from a purely engineering point of view as well as aesthetic considerations. Four plate box girders act compositely with a 300 mm-thick in situ reinforced concrete slab, and vary in depth between 1.2 m and 2.5 m. Steel was used principally to suit the type of design needed to keep overall dead weight to a minimum, and also to meet a requirement for early completion. Movement of the structure is accounted for at abutment points. The bridge is pinned with a fixed disc bearing at the southern river pier (two of the piers stand in the Nene River near the banks), and all other supports comprise ptfe stainless steel sliding bearings with side restraint. Details of surface finishes are given. (TRRL)