The project occupies one of Manchester’s prime city centre locations, opposite the Civic Centre and facing both the Grade I listed Town Hall and Grade II listed Central Library.
The high civic importance, heritage and visibility of the site resulted in an intricate and challenging planning context, demanding a high-quality building.
The key driver for the structural design was to provide highly flexible column-free accommodation that would be attractive to potential tenants. The typical beams are 730mm deep and, over the 18m span, vibration was a key criterion governing many of the section sizes.
“Only by using cellular beams could the 18m spans be accommodated while maintaining the required floor-to-ceiling heights,” says SimpsonHaugh Partners Architect Simon Critchley.
At ground floor level the architectural intent was to provide a colonnade with columns at 12m centres and cantilevers of 6m at either end. Continuing this wide spaced gird on the typical floors above was not economic and a number of options were considered.
Considering the buildability and cost implications a transfer structure at the lowest level was the chosen option. This greatly simplified the buildability and allowed a considerable service zone, which was required to support the servicing strategy.
Structural engineer: BuroHappold
Steelwork contractor: William Hare
Main contractor: Laing O’Rourke
Client: Mosley Street Ventures LtdTo maximise the spatial experience of the colonnade at ground floor level the columns are double-height, with the first floor set-back from the perimeter.
Long-span transfer beams at level two achieve this with the first floor hung from above. A similar arrangement is adopted at level ten with transfer beams that support the set-back columns above. This arrangement provides a high value terrace space overlooking the civic heart of Manchester.
Supporting the façade presented a number of engineering challenges. Each unit was constructed in 6m wide by 4m high mega-panels which were supported vertically at the base and tied laterally at the head. Mega-panels are supported by stubs directly back to each steel column, allowing a slender perimeter edge beam, coordinating well with the fenestration.
The use of a structural steel framing solution was a key element in the project’s success as Laing O’Rourke Project Manager Tim Brown says: “The obvious win was speed of procurement and erection, as the client had a deadline to get the building open in order to secure a Blue Chip anchor tenant.”
“Technically, by using steel the designers were also able to create a large double-height main entrance for the high-end reception area.”
Summing up, the judges say this scheme of new Grade A offices in the heart of Manchester’s civic centre responds to the challenge of this site of prime importance. Not only does the glazed stone tracery respond appropriately to the location, but the elegant steel-framed building with 18m clear spans provides flexible accommodation highly attractive to tenants.
Photo: © Daniel Hopkinson