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The Forth Road Bridge is located in Scotland, connecting Fife and the north east of Scotland with capital city Edinburgh and the south. When the bridge was opened in 1964, it was the fourth longest in the world, and the longest outside the United States, with a main span of 1006 meters between the two towers. In total, the structure is over 2.5km long.

Maintenance to the Forth Road Bridge is ongoing and a large capital programme to strengthen the bridge is also continuing. In 2009 the Forth Estuary Transport Authority (FETA) embarked on a competitive tender process for the Viaduct Bridge Bearing Replacement project, estimated to total £15 million.

The contract is the biggest single contract awarded since the bridge opened. It has involved the replacement of all the mechanical bridge bearings on the Forth Road Bridge’s north and south approach viaducts, which sit at either end of the bridge on each shore, connecting the A90 and M90 with the main body of the suspension bridge. The steel bearings support the bridge deck and enable it to move as required by changes in temperature. The contract also required an extensive overview of the concrete pier condition in conjunction with concrete repair works and the installation of an impressed current CP system.

Freyssinet was chosen to design, supply and install the bridge bearings, and complete associated concrete repair and cathodic protection works on the structure, having demonstrated a successful track record with this type of work.

40No. permanent mechanical bearings were specially designed to BS 5400, and manufactured in Freyssinet Ltd’s factory in Telford in quality controlled conditions that exceed the requirements of BS EN ISO 9001.

Freyssinet also designed and supplied 35No. temporary support bearings and over 100No. hydraulic jacks to meet the requirements of the temporary support and restraint works. In addition Freyssibar, Freyssinet’s own high-tensile pre-stressing bars, was supplied and stressed to assemble and fix the longitudinal restraint frames onto the structure.

Freyssinet were responsible for all the hydraulic jacking and monitoring of the bridge deck to allow removal of the existing bridge bearings. The bridge bearing replacement work by Freyssinet considered also the careful coordination of hydrodemolition works, steel cutting and drilling, and heavy lifting and positioning techniques to all allow the careful and safe positioning of each bearing into an extremely restricted access gap.

The impressed current CP system utilised three anode systems; titanium mesh, titanium ribbon and discreet mixed metal oxide anodes. In addition, galvanic anodes were installed into repairs outside the impressed current zones.

Over 14,000m of titanium ribbon anode strip was installed into the concrete faces of the pier head cross beams and legs to form part of the CP system. Freyssinet introduced an innovative technique that utilised a special chase cut into the concrete using a remote operated wall saw. This cut up to 60m per day without exposing operatives to excessive hand arm vibration or concrete dust.

Corrosion Control Services (CCSL), a sister company of Freyssinet, were involved in the procurement of specialist materials and supplied the necessary specialist site supervision / technical commissioning as required by the contract

The Forth Road Bridge is a category ‘A’ listed structure and consent had to be granted for the works to be carried out. Selection of all repair materials and methods of placement were carefully considered in technical trials prior to the start of the works in order to meet the requirements of the consent.

Freyssinet’s Northern Area Manager, Paul Wood, says “Works have progressed well, and are projected to successfully complete in August 2012, on time and within budget.”

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The services offered include identification of the bridge bearings, condition assessments, and advising on the practicalities of refurbishment, and/or bearing replacement. As part of the service, a comprehensive report is available, which would be photographically illustrated, and available in an electronic format as necessary. This allows the client to integrate our report into their own tender documentation and reports as required.

Freyssinet are the leading bearing manufacturer and experts in the fields of bridge bearing replacement, you can be assured that your new bridge bearings and bridge bearing replacement works will be of the highest quality. Freyssinet offer the full range of bearing manufacture and bearing replacements, both elastomeric and mechanical, from their UK factory. The designs are to BS 5400, and the quality control of bearing manufacture and bearing replacement exceeds the requirements of BS EN ISO 9001.

The team of leading designers at Freyssinet are able include suitable modifications into original designs of bearing manufacture, so that later bearing replacement operations can be made easier.

The replacement of bridge bearings and other operations, such as bridge expansion joint replacement, require extremely specialised jacking and propping solutions to facilitate the work. Freyssinet can offer a wide range of appropriate techniques, no matter how demanding or challenging the situation is. Freyssinet are able to supply vertical jacks to prop up structures, and also horizontal jacks, to facilitate movement of structures.

1000 tonne capacity, hydraulic jacks are available from Freyssinet with locking collars and swivel heads. To complement these, Freyssinet can use their manufacturing expertise to add to the jack heads, elastomer and PTFE sliding surfaces. These surfaces give the jack heads the ability to accommodate a limited amount of horizontal, and vertical, structural movement.

For both permanent and temporary situations, Freyssinet also supply flat jacks up to a 1000 tonne capacity, which are able to be used in gaps of 50mm or even less. For temporary solutions, where removal of the jack will be required, the inflation would be with hydraulic oil. If the bearing is to be used in a permanent situation, such as structural lifting or bearing pre-loading, a cementitious grout may be used. Alternatively, at a later date, the grout can be transfused under load if the situation requires.

Control over the entire jacking operation, can be monitored either manually or electronically, offering extremely high levels of control. The jacks can be grouped together into complex circuits, where they can be operated either in groups, or individually as required.

If the client has specified a more conventional propping system for a temporary situation, Freyssinet’s in-house designers are well placed to accommodate this, offering big advantages in terms of cost, speed and access. Propping also eliminates the need for excavation and temporary foundations.

Whether you require experts for bearing testing, or a bearing manufacturer for a bridge bearing replacement project, Freyssinet’s are the ones you should turn to.

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The scheme, part of the Highways Agency Area 6 Framework, was the scheduled replacement of two mechanical bearings 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 Ltd 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, 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 2no new mechanical sliding bearings, designed and manufactured by Freyssinet Ltd. Each bearing weighed approximately 3Tonnes and had a vertical capacity of 1600Tonnes at SLS.

The deck was handed back to the Client 2 hours ahead of schedule. Works were completed to the satisfaction of the Highways Agency and Jackson Civil Engineering, on time and within budget.

Why not learn more about Freyssinet’s bridge bearing replacement services for both repair and new structure projects?

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