Royal Mint Gardens
This heavily constrained site is on Royal Mint Street, close to the Tower of London and adjacent to Tower Gateway DLR station. The residentially-led mixed-use development will comprise a crescent-shaped, thirteen-storey block containing 200 apartments, with retail and office space on the lower levels.
The presence of Network Rail viaducts and DLR tracks across most of the footprint of the proposed building require innovative structural designs to unlock the site. These major infrastructure constraints have led to great complexity in the design of both foundations, and the lower levels of the building. Approximately 30 % of the site footprint is available for foundations, with the rest inaccessible. A deep cut-and-fill excavation by DLR arcs across the southern part of the site, and the viaduct alongside Network Rail tracks on the Fenchurch Street line runs along the northern boundary.
Given air rights over the obstructions, the lightweight steel-framed building will utilise piled foundations placed wherever possible, in combination with a large-scale cantilever system supporting the upper ten storeys of the building.
Braced steel cores extending to the full height of the building will be arranged in alignment as close to the viaduct as possible. These will provide support for cantilever trusses which extend out 15 m to either side, bridging over the existing railway, acting as a balanced system. Approximately 15 × 50 m of the building, ten storeys tall, is supported in airspace over the railway lines.
In the south-west corner, where the DLR tunnel portal is situated, a three-storey raking column and compression strut system has been developed. This stabilises the structure, whilst leaving the residential floors free to take advantage of the prime views of the Tower of London.
The whole building is also to be isolated from ground-borne vibration using steel isolation springs which are designed as an integral part of the structure. The entire concept for the design has been conceived around minimising the interface with the live railways and the need for track possessions.
Heavily constrained development with ten storeys cantilevered over existing railway lines
£ 100 million