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Light and fast construction: ArcelorMittal steel solutions for Doha's Aspire Tower
Steel was the only viable solution for the construction of the Aspire Tower as lightness of the structure and speedy assembly were the crucial requirements for the project. ArcelorMittal supplied rolled steel sections and composite flooring deck for the light flooring structure that protrudes from the tower's central concrete core.
For the occasion of the 15th Asian Games in December 2006, the 300 m Aspire Tower or Sport City Tower was built in the Sport City Athletic complex in Qatar’s capital Doha in order to support the flame.
The Aspire Tower houses a large reception and public area for 3000 people on two floors, restaurants and business centres, a 17-floor five-star hotel with 136 rooms, a sports museum covering three floors, a health club on three floors including a cantilevered swimming pool 80 m above the ground, and presidential suites, as well as a revolving restaurant and a two-floor observation deck.
Resembling the shape of a torch, the hyperbolic tower is crowned by the flame cauldron supported by a cone and protected by a 62 m high lattice shell structure.
The tower was erected on a 7 m thick raft foundation. Due to the existance of weak chalk within the limestone ground, it was necessary to pile the raft in order to ensure the full load capacity.
The core structure of the building consists of concrete with diameters of max 18 m and min 13 m, reaching 238 m into the sky and supporting the different modules.
The cantilevered floors of the different modules are supported by a steel structure: steel beams support the composite floor systems combining the beneficial features of steel and concrete. During the assembly and concrete pouring stage, the steel deck, provided by ArcelorMittal Construction, was used as a self-supporting formwork and provided a working platform. In the composite stage, the deck was structurally combined with hardened concrete (composite action) and completely or partially replaced the reinforcement of the slab.
The general arrangement consists of beams spanning radially between steel columns and a concrete core with circumferential secondary beams.
Transfer arrangements cantilevering from the core hold the steel columns in each module.
Some modules are sustained off-core by steel cantilever brackets at the base of each accommodation block (presidential suites, sports museum, restaurant floors, and lower observatory level) which also support the external cladding.
The upper observatory level is cantilevered with reinforced concrete directly from the top of the core.
A system of vertical trusses is responsible for the support of the 17-floor hotel block. Due to the greater loads in these areas, an additional level of wall bracing was necessary under the lift lobby and the swimming pool.
Cladding and its support system
The tower is entirely enveloped in mesh of stainless steel of varying permeability, including the void spaces between the different accommodation modules. Its design suggests tranparency and lightness. With a higher density on the southern face, this mesh also acts as a sunbreaker.
The hotel lobby is fully glazed as it is subject to wind load and has significant thermal performance requirements because the upper part gets hot.
Acting in catenary and prestressed within individual frames, spanning vertically between the horizontal ring trusses, the cladding is restrained either directly by the structural floors, by an arrangement of struts connected to the floors, or - in the areas between the modules - directly to the core.
Cantilevered swimming pool
The elliptical swimming pool (11 m long, 6 m wide, 1.5 m deep) is a reinforced concrete box with 0.3 m thick walls, supported by a 4 m deep steel truss structure which corresponds to the storey height containing the pool. The truss is connected to the core and supported on two columns that continue down to the levels below carried by the vertical trusses of the modules.
Extended about 12 m from the tower perimeter, the support positions for the truss of the pool and its deck are as close to the perimeter as possible in order to minimise the distance to be cantilevered and maximise the extension.
After the erection of the steel structure, the concrete pool was cast in situ. The total weight of the cantilevered construction is about 300 tonnes with the steel structure representing just 10% of the weight.
Internal concrete core
The core contains reinforced concrete stairs cast in situ, lift shafts, and open mesh access floors. The primary internal walls are made of reinforced concrete, while a secondary steel structure supports lift guide rails, etc.
The connection of the steel beams to the core consists of steel plates that are cast into the walls where the floor beams are located and anchored back into the core body. Then these embedded connection plates were welded in situ to the floor and transfer beams.
The Crown: Cone and petals
The Aspire Tower is crowned with the cauldron supporting the flame of the Asian Games: a cone shrouded by a lattice shell structure.
Apart from forming the lateral stability stystem, the diagrid also supports the cladding down to the restaurant floors.
The circular hollow sections forming the diagrid shell function as the primary loadbearing elements.
Some highlights of the construction phase
February 2006: first steel cantilever elements
July 2006: first elements of the cone
May 2007: first elements of the structure for cladding
15 November 2007: all 33 000 m2 stainless steel mesh deployed
The main structural elements of the tower were finished within 21 months in time for the 2006 Asian Games. After the Games, the work on the interior spaces continued and were completed in the first half of 2007.
Hadi Simaan (concept)
AREP - Etienne Tricaud (detail)
The Sports City Project/Government of Qatar
- Engineering Firm:
MIDMAC - Sixconstruct Besix J.V.