Structure as architecture
The Leadenhall Building was designed to lean away from St Paul’s Cathedral to avoid obscuring the view of the historic monument from Fleet Street. Achieving this was a feat of structural engineering. Because of its shape, the building leant sideways during construction. To counteract this, some of the sloping steel on the side faces was shortened to pull the megaframe back to the vertical. This began when construction of the 48-storey building reached the 19th floor and was repeated every seven storeys.
The Leadenhall building is a skeletal construction, with its steel and connections being on show. The megaframe connections were modelled and refined using 3D software, so the flow of forces through the connections was as efficient as possible.
As well as adding lettable space, the megaframe allowed for an ambitious construction schedule. Being able to rely on accurate machining of the steelwork meant large sections could be prefabricated, greatly reducing the time needed for construction on site. Accurate fabrication also meant that each floor’s table structures could be lifted into position with their services and floors already attached. In all, 85% of the finished building was prefabricated off-site.