The Marina 101 supertower
By Richard High17 February 2010
The under construction Marina 101 is a one hundred and one floor, 425 m-tall tower close to the Palm Jumeirah and the exclusive Dubai Marina megaproject.
The Marina 101 joins the exclusive set of supertall towers, those iconic high-rise buildings more than one hundred floors high. At the time of going to press Dubai counts "only" five supertowers.
The tower's central cast-in-place concrete core and the imposing columned facade are being constructed in record time with Doka's Platform SCP automatic climbing formwork, alongside its SKE 50 SKE 50 automatic climbers and folding formwork.
Scheduled for completion in 2011 when the first 28 floors will house a luxury hotel with 324 suites and 505 apartments on floors 36 and above, short cycle times for the cast-in-place concrete elements was essential for main contractor TAV Construction.
Doka's SCP system is "fine-tuned" for maximum efficiency, according to the company, with the site crew totally familiar with the routine, making a four-day cycle for each complete floor standard for the project. And with the number of concreting sections is high at 110, so any time savings on the carcass work are tremendously important.
But the SCP system also has another crucial benefit to offer. It leads the floor-slab formwork by only two floors, so the free headroom can be used to keep the work zone of the site's tower crane clear and unobstructed.
"That is a crunch factor for us and it helps us keep to the very ambitious schedule on this build," said Volkan Yerdelen, TAV's construction manager. "We have fewer climbs for the crane and that makes for a huge saving on time."
Perfectly timed work cycles
Doka's SCP climbs on eight hydraulic cylinders giving a total load-bearing capability in the climbing and working phases in excess of 45 tonnes. In addition, the platform climbs the formwork for all six shafts, plus a suspended stairwell tower for safe and speedy access to the working levels, along with two high-capacity concrete pump distributors.
For each lifting unit and concreting section, SCP's design means only two box recesses are needed to locate the supporting beams in the concrete structure. Other platform solutions, say Doka, need twice as many box recesses - all of which have to be locked into the reinforcing structure - and a significantly higher number of rams for climbing.
To maximise flexibility in the concreting process for the core, columns and floor slabs, the concrete pump's booms are climbed with the platform's climbing mechanism, but independently of the core formwork.
"We can climb the formwork and the concrete pump distributors separately, so there are virtually no mandatory-position points when we concrete. That gives us maximum versatility and, even more importantly, highly efficient material utilisation", said Siva Shankar Kanagasabai, TAV project manager.
On this project, climbing the SCP for the cast-in-place core and the SKE 50 brackets for the external wall sections separately proved the right strategy.
The six sub-level floors and the multi-level podium, which is a signature feature of the project, needed extensive cast-in-place concreting, but SCP could still be climbed independently, optimising material usage. The SCP's two working levels are fully enclosed for maximum safety and protection against the weather. It is permanently anchored in the finished concrete so lifts are possible even in windy conditions, so the construction schedule is rarely affected by adverse weather.
The central building core has no less than six shafts and is being formed with 815 m² of Doka's Top 50 beam formwork. The number of cycles is high - there are 115 concreting sections to be formed on this build - so the beam formwork is skinned with durable Dokaplex sheets. Steel formwork is being used at the corners to enhance durability even further.
Each anchor hole has extra protection, because here again a high number of re-use cycles is of tremendous benefit in terms of speed. These reinforcements proved more than worthwhile on the Burj Dubai build and enable the 400 m-plus of the supertower's cast-in-place core to be climbed with only one change of formwork sheeting.
The 32 columns in the building's iconic facade are being cast with Doka's high-end SKE 50 automatic climbing formwork. With one each side of the building, the climbing brackets are joined together to form a set so that they can all be climbed at the same time at the touch of a button.
The facade formwork has folding side panels for fast forming and stripping out times. The rear of each of the massively proportioned columns is being formed with hand-set Doka Frami framed formwork.
The forming crew strips out the Frami sections and simply places them on the two main working platforms of the SKE 50 automatic climbers, ready for the climb to the next concreting section. The routine is practical and efficient, and enables the column formwork and the formwork for the sides of the bottom joists to be moved up from level to level without any craneage.
The site crew from TAV Construction is using manual-set formwork for the massive cast-in-place bottom joists at the edges of the floor slabs. A mere 12 hours after the concrete is poured, the edge shuttering can be stripped out independently of the bottom-joist side formwork so that the crew can press ahead with the lead-in work.
That ensures compliance with the tight schedule in every phase of the work cycle and speedy progress on the build.