Gulf Construction Online - Doka helps build world’s tallest tower

Scaffolding & Formwork

Doka’s systems have been used on the Burj Dubai from the ground up.

Doka helps build world’s tallest tower

01 December 2005

Doka, which has established a firm footing in the region’s formwork market, is currently demonstrating its ability to develop and deliver customised formwork solutions to challenging projects by being involved with some of the prestigious and record-breaking projects in Dubai.

“Set to be the tallest building in the world, the Burj Dubai, in the UAE, is expected to present Doka with some highly demanding formwork challenges during the approximately two-and-a-half years that it will take to construct its shell,” says a company spokesman. “Inspired by an Arabian desert flower, the architectural form of the tower means that the formwork for the shaft core and wing walls needs to be highly adaptable. In turn, the extremely tight construction schedule necessitates an ingenious, streamlined utilisation plan.”
“Designed by the American architecture firm of Skidmore, Owings & Merrill, this skyscraper will boast a 575-m tall reinforced concrete shaft core, followed by a steel construction whose exact height has yet to be finalised. It will, in any event, be ensured that the building clinches the height record upon final completion in 2008,” he adds.
Elaborating on the project, he continues: “With its Y-shaped floor plan, the three-element tower thrusts upwards from a pyramid-like base, with setbacks occurring at each element in an upward spiralling pattern. Towards the top, the tower shaft tapers to form a finishing spire.
“Once complete, the tower will include a luxury apartment component that will house 3,000 people, a six-star hotel that will pamper guests with the utmost in Arabian hospitality, and the remaining will be made up by office space.
“Often varying from one floor to the next, the complicated groundplan of the building is one of the key formwork-engineering challenges in the construction of the shaft core and walls of the three wings of the building. No fewer than 180 pouring and climbing steps will be required before this reinforced-concrete construction can be completed. For each of these sections, around 5,000 sq m of Doka wall formwork Top 50 will need to be raised hydraulically, by 227 automatic climbers.
“The formwork concept developed by Doka in collaboration with the contracting joint venture of Samsung, Besix and Arabtec envisages climbing-steps being taken independently of one another in six separate zones, with work on the wing walls proceeding two to three storeys behind the central shaft core. “De-linking” the in-situ pouring operations from one another in this way (by dividing up the work into six mutually independent zones) makes it possible to construct the typical storeys of this imposing structure in a three-day cycle.”
“The Doka automatic climbing formwork is designed to withstand extreme wind speeds of more than 200 km/h, and is completely enclosed in a steel grille to provide the greatest possible safety for the crew at these dizzying heights. The Doka self-climbing system also takes care of raising the required four concrete placing booms – each up to 32 m long – from one floor to the next, independently of the crane.
“To facilitate handling of the two-storey-high prefabricated reinforcements, the Doka automatic climbing system is fitted with suitable reinforcement platforms which also make it possible to stabilise these high reinforcing cages.
“The specially-coated Dokaplex sheets, with their protective steel edges and corner elements, not only ensure first-rate concrete finishes but will also keep form-facing changes to a minimum, despite the high number of re-use cycles.”
“Following the pouring of the heavy foundations in autumn last year (also using Doka formwork), and the subsequent site installation work, the main formwork assignment got off the ground in March this year. Based on a custom-tailored concept featuring new Doka solutions for the SKE 100 climbing system and the Top 50 wall formwork system, the typical storeys will rise in a streamlined three-day cycle. A total of 154 storeys are to be formed and poured in this way by the end of 2007 - a world record not only for the contracting joint venture but also for Doka,” he adds.

JBR challenge
Doka formwork is also being used in Sector 6 of the Jumeirah Beach Residence (JBR) project in Jumeirah, where leading local contractor Al Shafar General Contracting Company purpose-ordered Doka formwork systems – including Doka Top 50 with climbing platforms and Dokaflex tables - for erecting four high-rise towers.
Using the formwork, the contractor has reached level 10 on two towers, level 6 on a third and level 3 on the fourth by mid-November.
Jumeirah Beach Residence, an impressive 22 million sq ft gross floor development along a 1.7 km beach frontage area in Jumeirah, situated on the shore side of the Dubai marina – includes a total of seven construction packages to provide 36 residential high-rise towers, four hotels and beach clubs to cater for a community of 25,000 people.
“Al Shafar’s Sector 6 contract features four high-rise towers with varying heights between 107 m and 172 m plus a 120-m-high building linking two of the towers,” says the spokesman. “The podium level is different from the other sectors in that it is a ‘stand alone’ podium and will be connected by a series of bridges to the other podiums.”
Al Shafar started work on Sector 6 in March last year with concrete pours for the raft foundation.
Project manager Ehab Edward Narouze explains: “The depth of the raft for the tower ‘foot print’ is approximately 2.8 m and 1.4 m for the general raft across the remainder of the site. For each tower’s raft, approximately 5,000 cu m of concrete was poured.
“Once the raft was complete, the contractor, using the Doka climbing formwork system, started work on the tower’s core shafts, working two levels ahead of the slab on each tower.
“The common podium across the site features a basement, grade level, a mezzanine, a plaza and upper plaza, with the lower three levels to be used for parking and the two plaza levels for retail outlets.
“Featuring a variety of heights between 3.50 and 3.75 m in the podium levels, with non-typical floors and different slab design and thickness, meant that the contractor achieved an 8 to 12-day cycle, using Dokaflex tables for the slab construction.
“Once clear of the podium and working on each tower, Al Shafar has been able to achieve a reduced slab cycle of seven to eight days depending on the floor being cast and six to seven days for the core shafts.”
“Typical floor heights of 3.4 m and walls are being poured using the Doka Top 50 system. Comprising just three components – timber formwork beams, steel walings and formwork sheets, the system is proving ideal for the project since all parts are reusable and can be optimised for most shapes and sizes,” he points out.
The system is also being used for the core shaft walls and includes telescopic shaft beams and Doka type 150F climbing brackets.
For slab construction throughout the Sector 6 contract, Al Shafar has opted for the proven Dokaflex tables system. As ready assembled tables, the system can be shifted in one piece to the next position without being dismantled. With fewer separate parts, formwork erection and striking are greatly accelerated; ensuring the shortest possible forming times for large areas of floor, the spokesman adds.
“Throughout construction, safety has been of prime importance to Al Shafar with Doka providing climbing scaffolds and platforms to ensure that all formwork, steelwork, cleaning and casting is done in a protected and safe environment; allowing the labourers to work with enhanced productivity,” he concludes.