Council on Tall Buildings and Urban Habitat
 The Leadenhall Building Technical Tour
Conference Technical Tour
June 13, 2013
Robert Lau

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LONDON - Developed by British Land and Oxford Properties, The Leadenhall Building is an exceptionally complex, 52-story engineering project undergoing construction in the heart of the City of London. The project team of Laing O’Rourke, Arup and Rogers Stirk Harbour + Partners explained how they have overcome extraordinary technical challenges through the implementation of innovative design and construction methods, driven by focusing on offsite manufacturing of building components. While there were several engineering challenges, the manufacturing and installation processes proved to be the highlights of the tour.
The site is quite constrictive, as are most sites in London. Ground for staging of materials was nonexistent. Street width and access controls determined the size and timing of delivering manufactured components, from steel sections to HVAC equipment. The longest steel section was 28 meters and the heaviest was 42 tons. However, the project team determined that factory-manufactured finished components were superior in quality to site-constructed components. As a result, the majority of installed items have been trucked from distant factories to this site with just-in-time delivery methods.

The vision of this office tower is to preserve the view corridor to St. Paul’s along Leadenhall St. As a result, the tower slopes away from this view corridor, toward the north. The north elevation forms the backbone of the tower by providing all services, elevator access, and structural stability. Complete sections of this megaframe were manufactured in factories, including the steel, HVAC equipment and precast concrete floor slabs. All steel was custom-fabricated, and fire-coated with intumescent paint at the factory. The sub-assembled modular components were lifted into place to form the 52-story structural megaframe, including 192 K-braces. The megaframe was intentionally installed out of plumb to resist the sloping lateral thrust of the south elevation as it rises along Leadenhall St.
The Leadenhall Building was nearly topped out
All steel columns and beams were custom-manufactured. The sloping exoskeleton is braced by the north megaframe, while six interior vertical columns support the office floors. Some nodes weigh as much as 21 tons. All field connections are bolted. The 3m x 4.5m precast floor planks are then dropped into position, and fixed into place on the steel beams via grouted rebar. Only required six installers were required per floor to place these planks, replacing the typical concrete crew that would be used to install a cast-in-place floor slab.
Delegates learn about the precast floor planks Tour attendees gather for a group photo
The building is double-skinned, using unitized cladding for the exterior rain screen and a double-glazed interior. The seven-story cavities are naturally ventilated to control the thermal expansion of the exoskeleton steel members. The unitized cladding was installed at the rate of 22 units per day. 

From an environmental viewpoint, the Leadenhall exemplifies a well-sited urban tall building. It contains few car parks, and many more bicycle and motor scooter spaces. There is also excellent public transportation available immediately nearby.
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