The A14 Orwell Bridge is situated to the South East of Ipswich, Suffolk. It is a 1.3km 18 span continuous twin post-tensioned concrete box girder viaduct, carrying the A14 Trunk Road over the River Orwell estuary. The scheme, part of the Highways Agency Area 6 Framework, was the scheduled for mechanical bridge bearing replacement supporting the North box on Pier Line 5, along with associated temporary works to facilitate jacking of the deck and to control the potential release of stored energy within the existing bridge bearings. Pier Line 5 is approximately 35 metres high.

Freyssinet was appointed by Principle Contactor Jackson Civil Engineering to design, manufacture and install the new bearings. Jacking and monitoring of the deck was also included within Freyssinet’s scope of works. The bridge bearing replacement works were carried out during a 52hour closure of the North Deck, carrying the Eastbound A14.

Prior to the possession, 3no jacking systems coupled with a computerised monitoring system were installed and commissioned to enable a controlled lift of the deck. The main lifting jacks were positioned on the pier top acting to the underside of the deck with a maximum uplift capacity of 3500Tonnes. Due to the reduced capacity of the bridge box at the jacking point, a further two sets of jacks were installed within the bridge box to effectively brace the box and resist the forces induced via the main lifting jacks. The sets of internal jacks used were Vertical Strut Jacks with a maximum capacity of 2240Te and Diagonal Strut Jacks with a maximum capacity of 1400Te.

Once the deck had been jacked to the required height, the existing bridge bearings were removed and replaced with 2no new mechanical sliding bearings, designed and manufactured by Freyssinet at the Telford factory. Each bearing weighed approximately 3Tonnes and had a vertical capacity of 1600Tonnes at SLS.

The deck was handed back to the Client two hours ahead of schedule. Works were completed to the satisfaction of the Highways Agency and Jackson Civil Engineering, on time and within budget.