Ouse Viaduct, Cambridgeshire

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Challenge

Mabey were approached by Interserve to supply propping at one of the piers under the A14 Ouse Viaduct. This propping would enable the complete demolition and replacement of the concrete crosshead and reinstatement of the bridge bearings.

Mabey were presented with a proposal by URS (the consultant working on behalf of the Highways Agency) involving the installation of stiff towers either side of the pier designed to resist all horizontal loads.

Following a review of the design brief and the loading information, Mabey engineers suggested an alternative simplified approach involving the use of a line of pin-ended struts either side of the existing pier, fully braced in the transverse direction, with all longitudinal restraint being provided by the existing piers.

Following discussions with Interserve, URS and the Highways Agency, this approach was accepted and resulted in cost and programme savings for all parties. Our solution involved Superprop and Mat 125 (Twin 610 UB) base beams, Superprop propping braced using Acrow panels and specially fabricated cross bracing, Twin 610 UB header beams, 38 Hymat hydraulic jacks with spherical heads (on varying height Mat 125 stools) and Mass 50 lateral restraints.

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Solution

The jacking was carried out by Mabey hydraulic technicians during a temporary road closure on the A14. During the jacking operation, the structure was monitored using LVDT sensors and pressure gauges connected to a pair of data loggers and viewed on a laptop computer.

Following completion of the concrete works, Mabey returned to dejack the structure and dismantle the propping equipment.

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