The "Grand Large" footbridge: new masts in Dunkirk

The design of a footbridge is an opportunity to design a unique structure while taking into consideration several factors such as the landscape, architecture and structural design.

The footbridge, “Passerelle du Grand large”, connects the beach of Malo-les-Bains to the new museum district of Dunkirk next to the marina, crossing over a 112 metre wide canal. With its original structural solution consisting of several pylons and tension rods it evokes the image of the masts of a boat.

Visually, it is shaped closely to a cable-stayed footbridge with several pylons of decreasing height that follow the sag curve of the main cable of a suspended footbridge. The structure is based on an “inverted Fink truss”.

The geometry and the tuning of the rods have been calculated to respect very simple laws. The tuning of the rod lengths has been calculated to avoid any compression in the rods at the Service Limit State. But the relaxation of the central rods has been permitted at the Ultimate Limit State. In this case, the footbridge behaves like two cantilevers.