Formwork techniques in race to keep time
Novel formwork techniques are emerging throughout the emirate, as contractors across the region strive to keep their projects within deadline. Christopher Sell casts his eye over the city to see who is doing what to keep ahead of the chasing pack.
Ongoing technological innovation remains prominent within the UAE construction sector as contractors stay at the forefront of formwork techniques in their constant battle with time pressures and demanding clients. All the big names within the industry have continued to evolve existing techniques, with the result being that major projects are yielding the results of such technology.
Meva, the German-based formwork specialist, is supplying what it claims to be the biggest share of on-site concrete works on the Burj Dubai - the floor slabs, covering a total of 224,808m2, or the equivalent of 33 football fields.
The company is supplying its slab formwork system MevaDec, which it claims is a complete formwork solution for the structural works involving 532 slabs for 153 floors - the initial target height of the Burj Dubai. Crucially, there are two factors that enable the teams to meet the current speed of one floor every three days; the MevaDec drop head with a quick lowering system, which allows stripping the panels and beams while the props remain as shoring, and the low weight, which allows the panels to be transferred to the next floor by using lifting gear. One further bonus is the local temperature, which barely falls below 25C and reaches almost 50C in summer, is conducive to rapid pouring.
Furthermore, the plastic facing of the formwork does not require replacing, not even after hundreds of reuses, whereas conventional plywood facing will give you perhaps 30 reuses, which consequently, on a structure such as the Burj, would need replacing approximately 15 times - a financially costly and logistically complex operation.
And it is not just the high-rises where contractors are employing novel formwork approaches to projects. Even on smaller, but equally high-profile developments within the emirate, pioneering approaches to formwork are being employed to enable contractors to meet tight deadlines.
During construction of the Palisades, the main contractor for the project, NCC has incorporated a unique cellular system into its plans, fully aware of the time-saving possibilities it affords them.
NCC also has a patented cellular system that will provide a more efficient process to manufacture the various buildings within the development. Mohammed Hasan, operations manager, NCC, says that steel formwork will be fabricated to match the building design, with the relevant room dimensions, wiring points and windows, and then filled with concrete. After three days the formwork can be dismantled, the structure is ready and the windows, and various internal properties can be fitted.
"It is very easy to do with steel formwork, you can do an entire villa this way, and specialist contractors can do the finishing works," says Hasan.
Doka has also been wasting no time in continuing to improve its existing products. Recently, Doka UK won ÃƒÂ¢Ã¢â€šÂ¬Ã‹Å“Product of the Year' at Building and Engineer 2007 for its newly developed Windshield system, which can safeguard slab-edges on several storeys at a time. To the inside, the trapezoidal sheet enclosure provides protection against strong winds and other unpleasant climatic influences, effectively ruling out weather-related downtime. By working inside an all-round enclosure, the site crew enjoy the best possible protection against falls from slab edges.
Furthermore, the system provides greater benefit on taller structures, where the wind loads increase as the structure rises. The standard version of the Windshield is moved up to the next floor by a climbing system that is guided up the side of the structure. This makes it possible for large units to be quickly, easily and safely moved into position. During this operation, the Windshield is fully structure-guided at all times. Once it has reached the desired resetting height, the system automatically latches into place.
As well as simplifying and speeding up the repositioning operation, this also ensures the very highest degree of safety at all times. The system also has the option of being raised to the next stage without crane assistance, by using hydraulic cylinders.
There are other examples where contractors are capitalising on the benefits that new formwork technology can give them on-site, providing means of swifter erection of buildings. One such example is ASGC's Emirates Crown Tower in Dubai Marina. Just one year from completion, the tower has adopted an efficient build cycle in no small part to the adoption of aluma formwork tables, which has enabled the tower to meet strict deadlines. "We have perfected it because we have done so many floors now," says Bishoy Azmy, deputy general manager ASGC. "Now we are working to a five-day cycle, before we were on 10-days, so it has been halved."
The speed of the construction is primarily the result of employing a hydraulic climbing system. This allows the core to be built a few days ahead of laying the slabs. When Construction Week visited the site in September, work was proceeding on the 35th floor for the core, while labourers were concerning themselves with the slabs for the 32nd. Allied to this, aluminium formwork is used before hollow core slabs (a prefabricated slab or prestressed concrete), measuring 12m by 120 cm are brought in. A crane is used to lift the precast slabs into position before steel mesh and seven centimetres of scree is then cast on top. "It is quite a laborious procedure as it has so many phases, but we have perfected it as we have done so many floors now," says Azmy.
Azmy acknowledges that the use of aluminium has budget implications but stresses this is offset by the benefits. "Aluminium is expensive but it makes the construction much faster, much easier and stronger. We care about the quality and safety of our work. So for us this justifies the cost."
Of course, faster construction leads to shorter build time, which is another avenue to recoup costs incurred.
And the recent drive by Enterprise Ireland Trade Mission to Saudi Arabia and the UAE has paid dividends with the announcement last week that Mivan, the Antrium-based specialist in fast-track construction techniques has secured $4 million worth of new business by providing formwork construction systems for projects in Dubai and Abu Dhabi.
These projects will be the 55-strorey Al-Fattan Tower at DIFC and the Marina Square Towers in Abu Dhabi, which consists of five 44-56 storey towers at Al-Reem Island, Abu Dhabi. Mivan's work will commence in March/April of 2007 and the structures of the towers will be completed by the end of the year.
Jim Laughlin, Mivan's regional managing director said: "These two contracts are the most recent in a series of similar projects involving our formwork system. Developers are attracted by the flexibility of the system and the opportunity it provides to bring very substantial buildings into full operation much faster than is possible using conventional building techniques."
Mivan is also working on the Burj Dubai Lake Hotel and the Dubai Pearl.