Bures Bridge carries the busy B1508 over the River Stour on the Suffolk/Essex border. It is a 20m span bridge with five curved cast iron beams and brick jack arches between.

The bridge was examined in mid 1990 and cracks were noted in some of the beams. Consequently the bridge was reduced to one lane with a weight restriction of just seven tonnes

Bures Bridge, Suffolk - Plate Bonding of Arched Cast Iron Bridge

Client....Suffolk County Council
Consultants....G Maunsell & Partners
Contractor...Balvac
Contract Value..£42,000
Programme...Sept/Oct 1991

Plate Bonding Raises Capacity to 40 tonnes

Several options were assessed and steel plate bonding was considered to offer the best value solution for the bridge. This important feature of Bures St Mary could be retained and its service life extended.

As the technique had not been applied to cast iron previously, full-scale trials were carried out on salvaged beams from a similar bridge that had been demolished. The trials proved successful and the scheme design was developed for the main works.

Sections of plate were bonded individually to the lower flange soffit of the beams with a bolted connection detail joining the plates. Edge clamps were utilised to provide pressure during adhesive cure.

Only a three week road closure was required to complete the full strengthening, rewaterproofing, refurbishment and reinstatement of the bridge.

Repair to the brick jack arches required resin injection and all of the cast iron elements were protected with a full coatings system. The bridge was reopened to full weight traffic and the overall appearance of the structure remained unchanged.

Information Courtesy of Main Contractors web site

Extract from "New Civil Engineer" publication - this is a more extensive explanation of the bonding process - large download file, please be patient.