Watermark Westquay

The Watermark Westquay footbridge in Southampton will connect the new Watermark retail centre to an existing car park.  The elevated bridge is 40 metres long and is 8 metres above Harbour Parade Road in the city. The bridge will give pedestrians access to a car park that serves the old West Quay shopping complex but also the new Watermark retail centre.

The steel bridge design is a box truss structure with a pattern in the side bracing. This efficient approach gives an enclosure for pedestrians and has spans of 30 metres between column supports and a 10 metre cantilever at the existing car park end.

The bridge was made from steel as it allows for a visually interesting style but it is also lightweight enough that it could be erected quickly from prefabricated component parts. This will minimise the need for temporary works and road closures in the area.

The footbridge was fabricated and assembled within the factory before being separated into two sections for delivery to the site. Installation took place during a closure of Harbour Parade so that a mobile crane could be positioned to lift the pieces into place. A temporary trestle was installed to secure the first section of the bridge. Once it was in place, the second section was lifted into place and a temporary connection was made until the joint could be securely welded.

The truss sidewalls of the bridge have diagonal bracing elements and one of the challenges was in achieving a uniform appearance throughout the length of the bridge. Thicker RHS bracing elements were used at the support locations with subtle local stiffening. Narrow and thick-walled chords were also used to give a visually shallow profile.

The horizontal bracing to the box truss’ roof and floor is in a similar, but less dense, pattern to the sidewalls and is formed with RHS elements of equal size to the RHS wall bracing. A steel deck floor is employed with an anti-slip deck treatment applied.

The vertical supports of the bridge are independent of the existing car park and new shopping centre structures at each end, and are located to minimise disturbance to the considerable amount of underground service routes in the area.