Repairs

Freyssinet Ltd. Innovation House, Euston Way, Town Centre, Telford, Shropshire, TF3 4LTPhone +44 (0) 1952 201901 Fax +44 (0) 1952 201753 Email info@freyssinet.co.uk

Hambrook Viaduct is situated near J19 of the M5 where it meets the M32 spur into Bristol. As part of a general strengthening and repair programme to the existing 6 No. piers and 4 No. abutments Freyssinet were contracted to supply, install and induce load into 312 No. elastomeric bearings and 104 No. mechanical bearings. 12 No. Shock Transmission Units (STU’s) were also fi tted.

freyssinet.co.uk

The replacement bearings were fi xed between newly cast bearing plinths and the deck soffi t using an approved system of bonding adhesives and epoxy mortars. Once a set of bearings had been installed at a pier or abutment location, load was induced simultaneously into all the bearings using a complex circuit of up to 52 No. permanent Freyssinet fl at jacks, installed one under each bearing. The structure was lifted by no more than 1 mm at each location. This uplift was continuously monitored at each bearing location with a system of mechanical dial gauges placed between the deck soffi t and the abutment shelf. The Freyssinet fl at jacks were initially pressurised with hydraulic oil and locked off in the temporary state. At a later date, the Freyssinet fl at jacks were then transfused hydraulically with a three part epoxy resin to form a solid mechanical packer under the base of each bearing. To complete the bearing installation sequence, the Freyssinet fl at jacks were protected by encasing them in a cementitious mortar surround.

The Transpec® SHT 550-100 STUs were installed as a measure to absorb any sudden longitudinal shock loadings from vehicle braking on the deck, and transfer the forces into the newly strengthened piers and abutments. Manufactured by Freyssinet, the STU expands and contracts with the structure over a thermal range of -18 °C to +35 °C and provides no resistance to the gradual thermal movement of the structure. Should any sudden shock load be induced longitudinally into the deck of the structure, the unit will lock up and become a load transfer mechanism. The load capacity of each STU is 550kN in both tension and compression. The STU’s are mounted within a bracket arrangement fi xed to the structure designed such that any subsequent repair or maintenance to the unit can be made with minimum disturbance to the assembly. Each unit was rigorously tested prior to delivery by Bochum University in an extensive test programme specifi ed by the client.

Bearing Replacement & STUsM4 Hambrook Viaduct

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Client

Highways AgencyArea 2 Consultant

W. S. AtkinsPrincipal Contractor

Norwest HolstSpecialist subcontractor

FreyssinetWork completed

March 2000Subcontract value

£185,000

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View on a pair of piers showing the new bearing installation

New bearings in position, plinth contains transfused fl at jack

Transverse loads are taken by side mounted bearings

Transpec SHT 550-100 Shock Transmission Unit

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