A striking curvilinear shape, 70 St Mary Axe is yet another distinctive landmark in London’s Square Mile. The 22-storey project featured a number of temporary works challenges. The primary challenge involved the temporary stability of the slip formed core. Two tower cranes were tied to the core during construction with one of the tower cranes subsequently replaced by a tower crane on top of the core. Extensive 3D modelling of the core was undertaken to ensure stability and verticality during the various construction stages.

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As well as a two-level temporary propping system for the basement construction, we also designed part of the ground floor slab of the building as a logistics slab on plunge columns to facilitate basement excavation operations. The logistics slab was strengthened to sustain the increased loading from the tracked excavator, muck-away truck and other construction plant.