FREYSSINET LTD CONTINUES TO EXCEL AT BRIDGE BEARING REPLACEMENT CONTRACTS 10 October 2011

Freyssinet’s origins are as a specialist in bridge construction and the manufacture of bridge bearings. Their knowledge and expertise in this area remain unparalleled. An extensive track record of bridge work illustrates their capabilities to complete projects both large and small, and always to the highest standard. During 2011 Freyssinet has sustained their success in this area, completing a number of bridge bearing replacement contracts throughout the UK.

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Freyssinet Ltd were appointed by Jackson Civil Engineering to design, manufacture and install two new mechanical bridge bearings on the A14 Orwell Bridge in Ipswich, as part of the Highways Agency Area 6 Framework. Jacking and monitoring of the deck was also included within Freyssinet’s scope of works. Overseen by Contracts Manager, Gavin Thomas, the bridge bearing replacement works were carried out during a 52hour closure of the North Deck, carrying the Eastbound A14, over the weekend of 11th-14th February 2011. 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 2 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 new. Each bearing weighed approximately 3Tonnes and had a vertical capacity of 1600Tonnes at SLS.

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In March Freyssinet Ltd commenced work in Peterborough, completing bridge bearing replacement and concrete repairs for Osborne Ltd on the A1260 dual carriageway. The road, also known as the “Nene Parkway”, serves as major trunk road from the southern end to the northern end of Peterborough, circumventing the city centre. The purpose of the works was to both prolong the life of the bridge structures and enable them to continue to cope with increasing levels of traffic. The works were considered essential by Peterborough City Council; if the bridges had deteriorated further the stability and integrity of the structures would have been compromised. A total of 7 bridge structures were included in this contract which involved the complete replacement of 12no pier crossheads on each of 4 bridges at two interchanges on the A1260 trunk road at Peterborough, and also associated concrete repair works. Concrete repairs were also carried out on 3 other nearby structures concurrent to the main works. Each bridge was a 4 span simply supported structure, with the deck being constructed from 28 inverted ‘T‘ beams, supported at each end on 28 elastomeric pads. The elastomeric pads were due for routine replacement and Peterborough City Council decided to re-design the pier crosshead and change the support at each span end from 28no elastomeric pads to 12no elastomeric pads and 1no mechanical shear key. This re-design would enable any future jacking of the deck to be carried out from the pier top removing the need for extensive steel temporary works. Bespoke steel trestles were erected on either side of the pier to be strengthened. The trestles incorporated 8no 250Tonne pot jacks with mechanical bearings on top of them to enable the deck to move and rotate during the works. The top 1.5m of the pier was removed using hydro-demolition and re-cast to the new design. New elastomeric pads were installed on the newly formed plinths. Once the new concrete pier head had achieved the required strength, the deck was de-jacked onto its new supports and the temporary works were relocated to the next pier so that the process could be repeated.

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Freyssinet Ltd was appointed by Birse Civils Ltd in April to carry out the scheduled replacement of roller bearings to 3no overbridges on the M27 motorway near Southampton. Bespoke temporary works were designed and installed by Freyssinet Ltd. The bridge deck was then jacked to release the load from the existing bearings, the existing roller bearings were then replaced with new mechanical bearings, which were again designed and manufactured by Freyssinet Ltd’s own in-house team. The main criteria for these works was to minimise the time period for traffic management on the M27, therefore in order to expedite the replacement process, the existing upper and lower casting plates were reused removing the curing process of new concrete & grout from the installation process. A new Highways Agency approved protective coating system was installed on these plates. As the existing upper and lower cast in plates were found not be horizontal or parallel to each other, compound taper plates were manufactured to create horizontal and parallel bearing surfaces; these plates were installed to very tight tolerances to enable the accurate installation of the new mechanical bearings.

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In June Freyssinet were selected by Southampton City Council to carry out bridge bearing replacement and concrete repairs on Itchen Bridge as part of a routine maintenance contract. Freyssinet Ltd acted as Main Contractor and the scope of works consisted of jacking and bearing replacement, protective coating, concrete repairs and all associated works, including temporary works and traffic management. Bespoke temporary works were designed and manufactured by Freyssinet Ltd incorporating high capacity hydraulic jacks. These were installed to support the deck during the works at the suspended span half joints and piers. A total of 22no mechanical bearings were replaced; 12no mechanical bearings at the free end of the suspended spans, 2no at the East Abutment and 8no at prioritised piers. All of the bridge bearings were designed and manufactured by Freyssinet Ltd’s own in-house team. The existing bearings were removed using high pressure water jetting and the new mechanical bearings were then cast into the structure prior to de-jacking the deck onto its new supports. Whilst these critical path works were ongoing, other ‘off-line’ works such as re-wiring the internal boxes and the installation of new expansion joints were undertaken. A total of 6no expansion joints were replaced on the bridge deck during one weekend closure of the deck. Maintenance was also carried out on all other bearings within the structure, including the application of new protective coating system. Re-profiling works were completed on the East and West revetments to the abutments, installation of high security access doors were installed through the abutment cheek walls into the abutment chambers and the internal box lighting systems were completely rewired. Concrete repair works were also carried out as necessary by Freyssinet Ltd’s specialist operatives. Each of these contacts was completed on programme and within budget, to the satisfaction of the contractors and the clients. Repairs and strengthening work, and bridge bearing replacement contracts in particular continue to represent a significant proportion of Freyssinet Ltd’s turnover, demonstrating their capabilities to continuously execute this type of work to a high standard.

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