Refurbishment of the old Medway bridge, UK

Abstract

The original Medway bridge, constructed in the 1960s, comprises 21 spans of pre-stressed concrete beams and twin three-cell box girder construction with an overall length of almost 1 km and a main span of 152·4 m. It carried both carriageways of the M2 motorway over the River Medway in Kent, UK. With the opening of the new Medway Bridge in August 2002 as part of the A2/M2 Cobham to junction 4 widening scheme for the Highways Agency, all traffic on the existing bridge was temporarily diverted giving Costain–Skanska–Mowlem joint venture (CSM) full access to the viaduct superstructure to complete the final phase of the structural refurbishment. This paper details the design of some of the final refurbishment requirements and identifies the solutions developed to overcome several problems encountered on site during the strengthening. Key items of work included replacing the entire suspended span over the river, repairing the supporting pre-stressed concrete half joints and re-assessing the approach viaducts. The work was completed under a fixed-price, design-and-build contract, which made the need for economic and buildable details all the more acute. Emphasis was placed on the development of flexible solutions to cater for anticipated variations on site.