First-of-its-kind footbridge rolls, tilts, and folds to let boats pass

In what looks like a fine engineering spectacle, a 180-degree rolling bridge makes way for boats to pass underneath. First-of-its-kind, the hand-powered opening footbridge is central to reactivating East London's Cody Dock, a huge ex-industrial dock located on the bank of the Lea river overlooking Canning Town, East London.

According to a release, since its decommissioning in the 80s, the dock was largely forgotten. It was rediscovered in 2009 and taken on by Gasworks Dock Partnership, who spent 12 years clearing, decontaminating, and restoring this historic dock.

However, reopening the dock to Lea's tidal waters for boats to pass through underneath was essential. This required the removal of a dam and the introduction of an opening footbridge.

For this, architectural designer Thomas Randall-Page sought Simon Myers of Gasworks Dock Partnership, who had planned a "traditional bascule bridge" for the site. Randall-Page proposed a new typology of a bridge.

The 12-tonne bridge can be opened in multiple ways

The unique bridge design is inspired by its Victorian forbears. They knew that "moving large, heavy structures efficiently requires that they are part of balanced systems, and this design works on the same principle of equilibrium."

The bridge can be opened in multiple ways - raising, swinging, sliding, folding, and tilting.

Toothed portals at each end of the bridge roll on undulating rails cast into the concrete abutments on either bank. Ballast fills the top of each square portal, countering the weight of the bridge deck that connects them, the release states. This very symmetry permits the bridge structure to roll through 180 degrees to a fully inverted position facilitating the passage of boats back and forth from the river to the dock.

The 12-tonne bridge requires no motors or electricity to operate it. Like a canal lock, two-hand winches manually power the opening motion.

The designer focused on the "element of surprise"

Made of weathering steel and oak, the bridge might seem simple and understated in its stationary position, but it is "celebratory and playful in its movement creating a spectacular and memorable event when operated."

"The idea for an opening bridge with a single moving part – the bridge itself – sounds simple but, as you can probably guess, was actually really hard to do," said Tim Lucas, structural engineer.

On either side, the deck is bound by lightweight balustrades woven from reinforcement bars. And when taller vessels need to pass, the elements are folded down flat to the deck before the bridge does its grand rolling movement.

"No one expects a square to roll; I find a childlike joy in this element of surprise," said Randall-Page.