Ocean Financial Center's 240 m core climbed in five-day cycle
By Richard High18 February 2010
A small site. tight construction schedule and challenging tower geometry meant Doka's formwork engineers would be pushing the company's formwork solutions to their limits. Richard High reports.
The 240 m-high Ocean Financial Center will be Singapore's first green-build office high-rise. A large solar-panel array and the first hybrid chilled water system in South-eastern Asia's financial metropolis will contribute to the eco-friendly lifecycle of the 850000 m² tower.
The architecture has the dynamic appeal of a shorefront facade inclined toward the marina and the design comes from world-renowned architects Pelli Clark Pelli, and the contracting JV of Obayashi and Woh Hup opted for a single-source comprehensive solution from Doka for the automatic climbing formwork used to erect the central cast-in-place (CIP) concrete core.
Crane capacity on site was always going to be subject to tight restrictions, so the formwork for the central CIP core was designed for maximum crane independence. On-site 84 of Doka's Xclimb 60 automatic climbing formwork brackets are dealing with the 55 concreting sections of the central CIP concrete core, which is further subdivided into six main shafts.
About 1.600 m² of Doka's Top 50 beam formwork are also being climbed in this way, dispensing entirely with craneage on this part of the build. The versatility Doka's system was the deciding factor in the project owner's decision to choose the Xclimb 60.
The manually controlled hydraulic cylinders enable the platforms for forming and for stripping out and for placing the reinforcement to be climbed in step with progress on the tower.The climbers move up section by section without delays or stoppages.
The formwork for the Ocean Financial Center's six shafts is also climbing automatically on Xclimb 60 brackets, again no craneage, which helps the JV maintain a five-day cycle for the concreting sections, each of which is 3.25 m-high.
Preassembly expedites progress
The density of Singapore means space was at a premium at the site. To help minimise the complexity of on-site logistics and keep the preparations in synch with the various trades, the platforms for the climbers were preassembled and delivered on a tightjust-in-time (JIT) schedule.
Two Doka foremen were on hand to support the site crew. Consequently, on-site preparation times for the automatic climbers were pared down to the bare minimum. The Doka foremen also familiarised the construction workers with every aspect of the correct routines for working with automatic climbers, laying the essential groundwork for smooth progress throughout forming and pouring.
It was important to decouple the entire concreting process on the central building core as effectively as possible from crane availability, so a concrete 13 tonne pumping boom was climbed alongside the formwork on a Doka SKE 100 automatic climbing rig.
"Crane capacity was very severely restricted, so by opting for this single-source automatic climbing solution for the central core and the shafts we cost-effectively sectioned off this part of the build and were able to adhere to the very tight schedule", said project manager Tan Lee Boon.
Protection shield for maximum safety
A top priority on the Ocean Financial Center project was a high safety standard throughout the carcass-work phase, in combination with short work cycles and speedy progress. In order to ensure a safe working environment when forming the floor slabs, the top four floors are enclosed by a large Xclimb 60 protection shield.
The shield also incorporates three working platforms so the lead-in work on the floor slabs is integrated into the construction routine. Like the formwork for the building's central core, the protection shield is climbed hydraulically from one section to the next.
The geometry of the Ocean Financial Center - a tapering front leaning toward the marina - posed a major challenge in terms of planning for the protection shield. The planners had to allow for the taper at the front, rear and sides, and for the backwards inclination of the protection shield.
With space and time both tight at the site Doka's engineers and the automatic climbing specialists adapted the shield to the structure's changing geometry directly on the tower. As the structure rises the climbing brackets and shield panels no longer needed on the forward-leaning front are lifted out and moved round to the sides.
This enables the protection shield to adapt to suit the continuously varying geometry and any changes can be made easily and without any loss of time.