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SSDA Awards

COMMENDATION – Haymarket, Edinburgh

Two steel-framed office blocks form an integral element of a scheme creating a new multi-use destination for Scotland’s capital city.

FACT FILE
Architect: Foster + Partners
Structural engineer: Arup
Steelwork contractor: BHC Ltd
Main contractor: Sir Robert McAlpine Ltd
Clients: Qmile Group, M&G Real Estate

Located next to Haymarket railway station, a £350M mixed-use development has created a new place to be in the west end of Edinburgh.

Designed by Foster + Partners, the four-acre site includes three Grade A office buildings, a 190-room hotel and a 172-room aparthotel, alongside provision for retail and leisure space.

Two of the office buildings, known as Buildings Four and Five, are separate blocks that are connected by a full-height 12m-wide glazed atrium.

With steelwork fabricated, supplied and erected by BHC, both buildings have been designed to span over the railway tunnels that serve the adjacent Haymarket railway station.

The southern portion of Building Four spans directly over the station’s northbound tunnel. Its central, 16m-wide office floorplate has been designed to bridge over the subterranean infrastructure and is formed with columns that are supported on piles founded either side of the tunnel. The structure’s main concrete core is slightly offset, positioned away from the tunnel.

Building Five, which sits above the adjacent southbound tunnel had to have a different design, as large diameter piles could not be installed on this part of the site.

When construction commenced on this structure, the ongoing groundworks and enabling programme meant that a large piling rig could no longer be accommodated and so a series of mini piles were installed between the two tunnels to support one of the structure’s lines of perimeter columns.

A Vierendeel truss, positioned from level three to level seven was installed to span the 30m distance over the tunnels. In order to erect this large steel element, a 9m-high temporary truss was designed and installed to support the steelwork above.

The Vierendeel truss was erected up to level seven with partially concreted floors and a predetermined jacking sequence was employed to ensure the structure achieved the correct tolerance before the de-jacking and removal of the temporary truss.

Each of the two building’s main cores are positioned alongside the atrium, which connects the two structures. However, complementing the cores and providing some extra stability, the buildings each have slim shear walls.

All of the office buildings have embraced sustainability as they have been designed to an EPC A rating and a BREEAM ‘Excellent’ rating.

The judges say the largest office building in Edinburgh has been constructed above two historic rail tunnels, while providing a colonnaded connection to a new public square. This has been achieved by an intelligent engineering solution that balances a steel frame calculated from the capacity of piles that could be “threaded” in between the two tunnels.

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