Major Bearing Repalcement Scheme for Southampton Council
CRL replaced 64 pot bearings on the Redbridge and Millbrook Roundabout Flyovers for Southampton City Council, which were failing due to increased loading, general wear and poor abutment drainage. All pier bearings other than the central fixed pier (which were prepared and painted), were replaced, involving excavation around the piers down to the top of the foundation and extensive propping.
The two flyovers support the A33 dual carriageway, which is the principal route into Southampton and it was crucial that traffic disruption was kept to a minimum. The road remained open throughout the course of the works apart from some night closures whilst the jacking was in progress.
The abutment bearing shelves had to be re-profiled to allow access for the jacking and bearing replacement. The fill behind the abutment walls was stabilised using permeation grouting and then the concrete removed using hydro-demolition. The bearing shelf and wall were then recast to allow access to the bearings.
The temporary works saw the bridges lifted in a controlled manner with precise computer controlled 24 hour monitoring.
The jacks were locked off whilst the existing bearings were removed using hydro-demolition. The new bearings weighed up to 450kg and CRL developed a specialist technique to position the new units with precision.
Once the new bearings were in place concrete was recast and the bearing plates grouted. At the same time the expansion joints on both bridges were replaced and a new drainage system installed.