|~|126proj200.gif|~|Construction started in May 2005 and is due to be completed by the end of 2006. The jumpform system is being used to do three-day cycles.|~|The Middle East is leading the world in high-rise construction. From the Burj Dubai, which lays claim to being the world’s tallest tower upon completion, to the recently-announced 1,000m-high Mubarak Tower in Kuwait (which looks set to snatch the title from the Burj) — no where in the world are high-rise construction techniques being tested so rigorously.
This unprecedented volume and speed of high-rise construction in the region is presenting untapped opportunities to revolutionise the way tall buildings are built.
Grocon is one such company that is looking to introduce its innovative high-rise construction systems to the fast-paced Middle East market. The Australian firm’s first project in Dubai is providing the core jumpform for the 330m-high Rose Tower, which is nearing completion on Sheikh Zayed Road.
ACC is the main contractor on the 72-storey project, which is steel floored with a concrete core. Work began on the tower in May 2005 and is due for completion by the end of this year.
And it was while working on the Rose Tower that Grocon achieved what, it claims, is a first for Dubai: three-day construction cycles.
“This is our first job in Dubai and already our system has proven itself,” says David Emery, general manager (engineering), Grocon.
“The floor cycle on the Rose is three days, which is the quickest cycle in the whole of the Middle East. This is just an example of the potential that exists with the shift work that you have here,” he adds.
Despite setting a precedent within Dubai’s construction market, Grocon is still aiming for bigger things: to achieve even quicker cycle times on the region’s high-rise projects by using its two-floor Lubeca jumpform system.
Grocon purchased Lubeca, a jumpform business operating in Singapore, around six years ago. After buying the Australian rights to the business and investing in R&D, the result is an innovative two-floor jumpform system that was developed using standard Lubeca components and hydraulic rams.
According to Emery, Grocon first implemented this system on the 82-storey World Tower in Sydney: “We had a lift core up on top which jump formed the core two floors at a time.” The system was also used on the 92-storey Eureka Tower in Melbourne, currently the tallest building in Australia. By jumping the lift core two floors at a time, Emery says its work on the project was in effect halved.
“We built Eureka Tower in about 47 operations — all the work that had to be done was basically halved i.e. half as much concrete placing and half as much steel fixing.
“It also means half as many joints in the core, so it is actually a more robust structure. And for some of these particularly tall buildings here in the Middle East, having a robust structure is vital.”
All of this presents significant cost-saving opportunities. For example, as the splicing of the reinforcements is only every second floor, this means less steel needs to be used. “Engineering inspections, surveying operations — everything is halved,” adds Emery. And as some of Dubai’s towers reach 200 stories, building them in 100 operations instead of 200 means a more efficient use of labour.
“It’s a lot more productive because everything is mechanised,” explains Emery. “When you construct all of the columns in a mechanised system you don’t need as much labour as you would conventionally. So it’s a more productive system — it not only goes quicker but relies on less labour.”
This can be beneficial with tall towers as it means there are fewer labourers moving up and down the building. “One of the problems with these very tall towers is vertical transportation i.e. all the materials have to go up and the men have to come back down again. But if you can build a building with fewer men to go up and down, then you’re onto a winner.”
On its Australian projects Grocon actually installed lunch rooms and bathroom amenities up on the top of the system: “Workers travel up and stay here for the day, again offering huge time saving potential.”
But one of the greatest challenges of high-rise construction — and one that is all too often overlooked in this part of the world — is worker safety. To counter this, Grocon is seeking to introduce its perimeter jumpform systems to the Middle East, which are used to construct the entire perimeter of the building.
“We build the columns and the beams ahead of the floor slabs and then we have trailing safety screens that hang four or five floors from the perimeter system.
“There’s access around the entire perimeter system for the men to steel fix and concrete down the columns. By using the perimeter system, the worker platforms are totally enclosed.”
While Grocon has used the system in Australia, Emery says it would be a first for this part of the world. “This technique has never been used before in the Middle East and could revolutionise the construction industry here.”
Grocon’s trailing systems can play an integral role when it comes to cladding a building. “It means we can install façade cladding and finish the building behind the safety of the trailing screens. In effect, we’re actually extruding a building as we go,” says Emery.
“In Dubai you often see these massive structures that stand 50 or so stories, but the façade is only being put on at the bottom. If the curtain wall façade is installed from behind the perimeter system’s safety screens, the building is always enclosed and is safe — no one can fall out or drop anything off the side of the building because there will either be the safety screens or the facade already installed below the screens.”
The system is raised via hydraulic jacking mechanisms that key into pockets in the columns, and the screens simply lift when the system itself jacks.
“The system jumps with the perimeter screens that hang down, and when it jumps there’s a finished building that comes out of the bottom,” says Emery.
“It’s also very accurate because it’s built as a system. Everything is tied and braced together so every time the system jumps, the columns and beams on the next floor are in exactly the same position as they were on the floor below, and isn’t relying on manual set out.”
There is great potential for this system in Dubai — especially given the emirate’s 24-hour construction site activity. “With the double shift working patterns that you have here, these systems could go to three or four days per floor,” says Emery.
“Lighting can be set up around the entire perimeter of the system on big poles shining down onto the deck so it could operate 100% productively during the evenings; and during the daytime, a shade cloth can be put across the top of the system to keep the sun off.”
According to Emery, the concept of three different work fronts operating at the same time is key to faster cycles. “The first work front is the lift core, the second is the perimeter system and the third is the floor slab — and they’re all happening simultaneously.
“The whole system raises itself in one go, men on the perimeter system are concreting and steel fixing the columns, and down below there are men concreting the floor slab. And if all three of these work fronts can operate simultaneously, you have a faster construction cycle.”
Grocon is preparing to finish work on Dubai’s Rose Tower — the structure has reached the 71st floor and the jump form system is due to be completed next week, after which time it will be pulled apart in modules and craned down. But the company is already on the look out for a project on which to implement its innovative high-rise construction techniques.
“There are two next steps for us: the first is to do the double jump form system where we build two floors at a time for the core,” says Emery. Grocon is in discussions with Tameer about using its system on the 106-storey Princess Tower planned for Sheikh Zayed Road, which is likely to stand around 420m high.
If Grocon wins the Princess Tower, Emery says the number of cycles could be cut in half, so instead of building the core jump form in 106 operations it could be built in around 54.
The second step for Grocon is to introduce its full perimeter system with the trailing safety screens to the region. “The concept of building the perimeter with completely mechanised systems and then putting the facade on inside that system as you go is a paradigm shift for the Middle East — it’s a whole new way of doing things.”
The pace of high-rise construction across the world means that methodologies and systems are constantly being pushed to their limits. Nowhere is this more evident than in the Middle East where projects are completed to the tightest of margins and briefest of timescales.
And as nearly half of all site accidents are caused by falls from height or by dropped equipment, any new high-rise system that incorporates extra safety features is likely to be met with a sigh of relief by the workers who actually build these leviathans.||**||