London will soon be home to Europe’s tallest, mixed-use ‘vertical city’ that is being developed by Sellar Property Group in conjunction with the State of Qatar. Designed by Architect Renzo Piano, this edifice begins above three massive levels of concrete formed basements and constitutes public areas, retail outlets, and a welcoming lobby on the third floor. The office areas will be seen up to the 28th level, above which, a few restaurants and a mid-level public viewing gallery have beenpositioned. The Shangri-La Hotel will fill in space from level 34–50, within which, the structure’s framing material changes from steel to concrete.
While the building is constructed using structural steel from the ground to the 40th floor, a concrete frame is predominant from the first level of the hotel’s bedrooms. The post-tensioned concrete frame is seen all the way up to the 69th level, not only encompassing the hotel, but also 12 floors of premium residential apartments that are serviced by the Shangri-La Hotel.
A Functional Design
The design of the Shard eliminates the need of dampers, as inherent properties of the building materials and frame types have been mixed and used cleverly. A vertical spine, with a cantilevered concrete core that was stiffened by a steel outrigger hat truss at levels 66–69, engage the perimeter columns of the building making it laterally stable.
As the building’s height progresses, its optimised perimeter columns’ location transfers with the height. This number goes from six metre spacing at the base, to three meter and then 1.5m at the very top. All of the vertical column transfers were optimised and achieved with no loss of space, and the perimeter columns were transferred using either a load sharing steel girder system or A-frames.
Not only is the Shard’s design feasible, it also comes with the promise of flexibility. Once complete, the office areas can be configured to various needs by removing partition walls, and by the enlargement of adjoining spaces. Since a concrete frame would have never allowed such flexibility in spaceutilisation, the inclusion of a steel-centric design was the answer.
|Shard's Finer Details
|Client: Sellar Property Group
|Steelworkers Contractor: Severfield-Reeve Structers
|Architect: Renzo Piano
|Steel Tonnage: 13000 Tonnes
|Height: 310 m in 92 levels
Wrapped in Steel
Severfield-Reeve Structures completed the largest part of the overall steel-work of the edifice, which began at the foot of the structure to level 40 and made use of about 15,000 pieces of steelwork weighing 12,000 tonnes. This milestone was followed on from an extensive demolition phase, and the installation of foundations and the slab. Steel has also allowed the office zone and the overall height of the building to be maximised with a floor-to-ceiling height of 3.65 m.
The Shard’s central core has topped out at level 72 which is the top floor of an upper viewing gallery. This gallery extends from level 69 to 72 and will be erected as part of the Severfield-Reeve’s steelwork erection programme, phase two. The second steel frame crowns the building and gives it a triple storey frame, for the upper viewing area, followed by a steel lattice frame for the spire, which will extend the structure upwards to level 87. A cantilevered frame for the glass cladding at the structure’s pinnacle will be added to take the building to its 92nd level— the Radiator as it will also house the heat rejection plant.
The fabsec cellular beams with 15m spans and services passing through them were deemed the most appropriate form of construction for the office, retail and a vast majority of public spaces. Steel framing is also used in the lowest levels of the hotel (from 37–40) where edge transfer beams are used to transfer loads from columns at 3m centres, to office floor columns at 6m centres.
Three locations at the perimeter on each office floor plate are called the winter gardens where the steel frame is exposed and the steelwork is detailed appropriately as an enhanced architectural feature. The floors within the winter gardens are detailed with Luxcrete-type glass lenses set into the slab units. The columns system, with its decreasing column spacing, requires the use of sets of load-sharing beams at various locations in the elevation. Acting as a load-sharing system, a Vierendeel truss system has been erected around the top of the steel framed sector (levels 37–40) that helps to transfer loads back to the core. The building’s columns have been designed to reduce weight and space with height adding to the impression of increasingly delicate structure tapering into the sky.
The ground breaking ceremony of the Shard took place in 2007, when it quickly set a record as UK’s largest continuous concrete pour for the basement slab. In December, 2010 it became the country’s tallest structure—ahead of schedule— when the 72-storey core was completed out of the proposed 92 storeys. The completion of the first 40 stories of steelwork by November, 2011 has been attributed to the undying cooperation between the entire construction team of workers and managers. The shell and core of the Shard is scheduled for completion in mid-2012, where it will stand tall as a befitting backdrop to the London Olympics.