MacMahon Bridge

Grand Canal Dock, Dublin 2

The design was for a 'through bridge', comprising five elliptical arches, three of concrete clad with megalithic limestone, and two outside arches of stainless steel, supporting a flat deck, of shallow construction to maintain headroom for the passage of canal boats below.

The outside arches are designed to carry flights of steps down to a new boardwalk at canal level, thereby generating the long shallow elliptical form of the outside arches. Design development lead to elimination of the central arch, while budgetary constraints have lead to the postponement of the stairs' construction. Pending the construction of the stairs, the 'refuges' at the middle of the causeway, shielded from the traffic by the limestone-clad arch-beams, are well used.

The configuration of the arches is based on a curtailed ellipse, with elliptical cross-section stainless steel fins holding two parallel composite stainless steel box-section curved beams. The technological challenges in manufacturing these sections with their streamlined stripes were significant. The beams also carry integral LED light strips, which cast light along the face of the glass balustrade guarding.

The main causeway required a motorway barrier. An elliptical profiled hardwood rail was added to a standard motorway barrier to create a people friendly guarding. Buff coloured granite paving completes the palette of materials.