St Mary Axe

London
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Story

A Landmark 22-storey office Building in London’s Central Business District

Affectionately referred to as the “Can of Ham”, 70 St Mary Axe is a strikingly curvilinear form that add another distinctive shape to the its high-rise neighbours in the “Square Mile”.  Located on the site of a former low-rise block of offices and retail units, the project was initially granted planning permission in 2008, with construction beginning in 2015. The project was completed four years later.

Our scope included the construction of a three-storey, 30m deep basement and a 90m high 22 storey concrete core, as well as the floors.

26,000m2 primary core
30 deep basement
22 Storey Slip form core
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highlights

SUBSTRUCTURE

Substructure works involved the construction of a perimeter capping beam, and the installation of propping over 3 levels, bulk excavation, waterproofing, and substructure concrete works.

To maintain the integrity of the waterproofing the 2.5 m deep raft slab was constructed in such as way that the rebar and concrete could to be placed continuously across the pours with no striking or ‘stop end’ preparation required.

ACCESS AND PROPPING

Surrounded by busy roads on all elevations, we constructed a gantry slab to service the works. Bulk excavation (part ‘top down’) was staggered with the installation of propping. Raking props installed from B2 enabled the slipform rig to be installed.

SPEED AND ACCURACY

Speed was of the essence on the 50-week programme, so we built the 22-storey core using a fully-cantilevered slipform system and optical plumbs to minimize any deviation to the core. We achieved the specified vertical tolerance +/- 25mm over the full height of the core. This was the tallest free-standing slipform construction we had ever undertaken. Climbing at up to 2.5m per day, we were able to complete the core five weeks ahead of programme, allowing the steel-frame contractors additional time on site. The installation of a precast composite roof slab enabled the crane to be installed onto the roof of the core and ‘Light tag’ concrete was used on the metal decks (over an area of 32,000m2) to reduce the weight of the core on the foundation.

OFFSITE FABRICATION

Due to the access and space constraints of the site we prefabricated the slipform rig at our offsite fabrication facility. This reduced the assembly time on site and enabled ongoing basement works to continue uninterrupted.

Project
St Mary Axe
Architect
Foggo Associates
Engineer
Contractor
Mace
Sectors
Commercial
Services
Basements
Location
London
Status
Completed
Project summary
Project summary
Project
St Mary Axe
Architect
Foggo Associates
Engineer
Contractor
Mace
Sectors
Commercial
Services
Basements
Location
London
Status
Completed

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