We have designed the simplest and most elegant way of stepping from one side of the Liffey to the other. A slender blade of stainless steel leaps from the reeds and rushes to cross over the river.
Our bridge is the most slender and shallow structural arch that is technically possible.
The arch spans the river without the need for intermediate columns, masts or suspension structures. The minimal
form is as flat as possible to allow the most inclusive access.
The shallow arch resolves the competing demands of:
• flatness for wheelchair access
• height for flood river clearance
• clearance over the path on the south bank of the river for pedestrians and cyclists
The structure reaches its most slender point at its apex at the centre of the river.
The simplicity of the design:
• minimises the disruption to the landscape
• distils the composition to a bridge springing from the greenery of the river bank
• maximises the ‘aesthetic longevity’ of the bridge, by being a product of the act of ‘crossing the river’, rather than of more transient motives of ‘style’
The design achieves the 2.0m clearance over the path for pedestrians and cyclists and 2.1m clearance over the river required by the brief. The permeable parapets will permit river flow across the top of the bridge deck in the event of high flooding. The minimal vertical sides of the bridge deck will present little obstruction to floodwater.
Pedestrians and Cyclists
We have assessed that a 6.0 metre width accommodates the peak flow of unsegregated pedestrian and cycle use. This compares favourably with other bridges in similar use, as well as complying with current regulations.
Minimum Ramps
We have avoided the need for extensive and obtrusive ramping on the river banks. On the south bank, the bridge spans over the existing path thus maintaining it for pedestrians and cyclists, while on the north side, the new entrance plaza is gently sloped up to the bridge landing.
Accessibility
The bridge never exceeds a gradient of 1 in 20, optimising accessibility for wheelchairs and pushchairs. The north river bank landscape and Entrance Plaza is gently ramped to provide step-free wheelchair and pushchair access from Chapelizod Road.
A New Entrance to the INWMG
The existing footpath on Chapelizod Road will be lowered and a ‘shared surface’ provided to form a new entrance to the Irish National War Memorial Gardens. The new entrance gates take inspiration from the ‘reeds’ on the bridge and are wide enough to allow vehicles to access the Entrance Plaza, providing sufficient area for receiving dignitaries during formal events.
Secure Boundary
A face-packed gabion wall, filled with reclaimed Dublin Calp Limestone provides a secure boundary to Chapelizod Road and the UCD Boat Club. A gate is provided in the gabion wall for maintenance access. and, as it approaches the river, the gabion wall is replaced with a ‘reed’ fence to provide a visually lighter but equally secure boundary at the river’s edge.
Materials, Finishes & Composition
The bridge structure has been designed to be constructed using structural plate consisting of a mild steel core with a stainless steel outer layer (clad-steel). This provides the combined qualities of durability, structural efficiency, corrosion resistance and economy. It has a shot-peened stainless steel finish which increases corrosion resistance, and provides a soft, light-reflecting surface.
The elements in contact with people are given a more tactile quality, with references to the War Memorial Gardens and the landscape of rushes and reeds along the river bank.
Traces of footprints in the bridge deck call to mind those who have walked before us and did not return. The footprints are imprinted within the stainless steel deck plate via a process of explosion-forming. The finished surface is lightly textured providing an anti-slip surface. This is laid to falls, transmitting rainwater to the edge channels from where water is transmitted to the ends of the bridge. An acoustic interlayer between the walking surface and the structural deck provides sound absorption underfoot.
Poetry will be an important part of the bridge but how this is incorporated and the selection of poems will be reviewed in detail with the Client at the next design stage.
A parapet of stainless steel ‘reeds’ is visually translucent, fluid and soft to the touch. The ‘reeds’ are highly transparent and gently reflective: they will catch the sparkle of the river and the colours of the changing sky. The scale of the individual reeds can be developed to suit the final desired visual appearance. At the next design stage, the density and distribution of the reeds will be ‘tuned’ to achieve a balance of transparency and light-catching qualities without compromising safety.
A timber leaning rail is provided along the middle third of the bridge span, encouraging users to stop and enjoy glimpses of the river.
Sustainability
Minimising resource use is the fundamental quality of sustainable design. By using the minimum material, and maximising its engineering performance, our bridge proposal will consume less resources. Steel is a highly recyclable material. The design has a 120 year design life, however when it is eventually removed the material can be re-used in a continuing life-cycle.
Where we gently sculpt the riverside beneath the ends of the bridge, the bank is faced with reclaimed Dublin Calp limestone. The position of the bridge has been determined to minimise the removal of trees, and to leave the least visible imprint on the river bank. The foundation form has been designed to lie within the river banks.
Light
The shot-peened finish of the edges and underside of the deck structure provides a light ‘catching’ surface. This will render the qualities of the ambient light; at certain times the bridge profile will radiate back a blade of sunrise or sunset across the river, or reflect the softer light of dusk.
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Materials, Finishes & Composition
The bridge structure has been designed to be constructed using structural plate consisting of a mild steel core with a stainless steel outer layer (clad-steel). This provides the combined qualities of durability, structural efficiency, corrosion resistance and economy. It has a shot-peened stainless steel finish which increases corrosion resistance, and provides a soft, light-reflecting surface.
• Bridge length: 62m
• Bridge span: 47m
• Bridge width: 6.1m
Client: Office for Public Works
Completion Date: 12/2022
Gross Floor Area: 1090m²
Budget: Confidential
Architects/Landscape: Ian Ritchie Architects Ltd
Engineers: Schlaich Bergermann Partner
Lighting Consultant: Ulrike Brandi Licht
