Widening and Strengthening
Mildren Construction were appointed by Hampshire County Council and the West Berkshire County Council to widen and strengthen Knights Bridge. The bridge carries the A339 over the River Enbourne.
The A339 is classified as a Heavy Load Route, serving as a part of the national interlaced network.
This structure had reached a point where major strengthening was required, with the highway alignment, carriageway width and containment parapets also all well below current standards.
The works comprised of widening of the bridge on the north east side with twin span brick faced concrete arches and brick faced cantilever steel sheet piled wing walls. Widening of the A339 on the approaches to the bridge (including associated drainage, street lighting and signing), strengthening of the existing brick and mass concrete arches with reinforced concrete saddles, building new brick parapets on the upstream and downstream sides and constructing a sheet piled retaining wall to support the north west embankment.
The structure had to be extended between 1.5 and 2.1 metres to the east the carriageway and realigned 70 metres in each direction.
The wing walls are brick clad cantilever sheet piles, the abutments and arches are brick clad mass concrete; replicating the existing brick elevations.
To the Northeast a sheet pile retaining wall was constructed to support the widening of the carriageway. Once widened, the existing brick arches were strengthened with concrete saddles and then waterproofed.
The A339 had to remain open during the works, which is why we proposed a traffic management plan of reducing the road width to a single lane controlled by traffic lights and a speed restriction of 30mph. Pedestrians were diverted onto a temporary footpath and footbridge to the south of the existing bridge.
Working closely with the Environment Agency was essential to the successful delivery of this project, as they have an in-depth understanding of the river and its surrounding environments.
Value of development
NEC 3 Option B
Live working environment