Major milestone reached for three-legged bridge

17.12.2018

A new Y-shaped footbridge has been lifted into place across the Grand Union Canal in Milton Keynes.

The COWI/Knight Architects-designed structure is part of Crest Nicholson's Campbell Wharf development.

The 35-metre bridge will allow pedestrians and cyclists to cross the Grand Union Canal between the new mixed-use development and marina.

Bespoke solution

The design team developed a highly bespoke solution to span both the canal and marina entrance with one structure.

The main span of the bridge aims towards the marina entrance. Two thirds of the way down the deck length, it splits symmetrically to north and south, framing the marina entrance and linking the leisure routes and towpath on either side.

This unusual three-legged design provides two connections within one structure while avoiding any abrupt changes in direction that would be difficult for cyclists and wheelchair users to navigate. The layout also provides a platform over the canal where people can stop to watch the narrowboats below.

Complex geometry

Principal Engineer at COWI Oliver Stross commented: "The deck cross-section consists of a central steel spine supporting the 3.2-metre wide deck, enabling the majority of the steelwork to remain planar despite the bridge's complex geometry.

"The bridge's parapets reflect the reeds and rushes found along the banks of the canal. The team used 3D parametric modelling to develop the geometry definition, giving each parapet panel a unique pattern.

"We worked collaboratively with the steel fabricator, SH Structures, to ensure that the design was achievable within the project's budget; we developed several prototypes to test and refine the design, which is laser cut from 8mm thick weathering steel plate.

"We used careful detailing throughout the design to produce an understated structure that allows the parapets and activities on the waterway to take centre stage."

Designing for construction

"To meet the project's programme, optimising the design to enable efficient construction was a key consideration," adds Stross.

"The span lengths and deck weights were carefully controlled so that the deck could be fabricated off site before being assembled and lifted into place as one piece by contractor Land & Water using a 750-tonne crane. This approach minimised the disruption to marina works and the canal traffic."

The bridge is due to open to the public in summer 2019.