The challenge
We were presented with a proposal by URS (the consultant working on behalf of the National Highways) involving the installation of stiff towers either side of the pier designed to resist all horizontal loads.
Our engineers reviewed the design brief, loading information and suggested an alternative simplified approach. This involved the use of a line of pin-ended struts either side of the existing pier, fully braced in the transverse direction (right angle to the direction), with all longitudinal restraint being provided by the existing piers.
Following discussions with Interserve, URS and the Highways Agency, the simplified approach was accepted and resulted in cost and programme savings for all parties. Our solution involved Superprop and Mat 125 (Twin 610 Unversal Beams) 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.
Our solution
The jacking was carried out by our 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, we returned to dejack the structure and dismantle the propping equipment.
