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In the Estonian capital Tallinn, the two construction firms Merko und Kontek are currently erecting a 112 m high residential and hotel building, in an 11-month construction period for the shell. Above a 4 / 6-storey podium, the complex separates into two equally high towers, one of 31 storeys and the other of 33. The multifunctional guided climbing system GCS from Doka has made for very safe working conditions and swift construction progress on this project, even during the winter.
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The short construction period allowed for the shell called for a streamlined in-situ concreting workflow coupled with safe working conditions, so as to achieve fast cycle sequences and to minimise weather-related downtime during the winter months. Launched in August of last year, this construction project must be finally readied for occupancy by April 2007, meaning that its structure shell will have to be completed by the beginning of July 2006. There could be no question of discontinuing construction work during the winter, of course. Instead, the contractors looked for cost-effective ways in which the wall and slab forming works on both towers could be speeded up while still being carried out under safe and (even in winter) tolerable working conditions.
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The GCS system from Doka offered an ideal solution in two different regards, explains project manager Hannes Stolzlechner of Doka: “The windshield is designed with a guided climbing system, and makes a perfect job of screening off the slab-edge zones to the outside on three storeys at a time.” This means that the accident-prone slab-edges are given the best possible safeguarding, and that the top three storeys at any time – where the forming operations have to be carried out – are optimally protected against wind and weather. In this way, work can be moved ahead rapidly here. “And for the exterior walls”, adds Hannes Stolzlechner, “the guided climbing system GCS can be used in just the same way with Top 50 wall formwork as with the windshield (for screening off the slab-edge zones). In other words, you can raise both the windshield and the wall formwork units together, using one and the same system”. This simplifies equipment commissioning and assembly, and speeds up repositioning operations in both cases.
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“When you have to climb 33 storeys, like here on the Tornimäe project, then it pays to use the Windshield system right through the whole course of construction, on every single storey” notes Hannes Stolzlechner. “After all, you only need to erect it once, and then all you have to do for every climbing operation is just get the crane to pull it up.” The system is firmly attached to the structure at all times, and latches automatically back into place with its integral gravity pawls at the end of the climbing lift. The Windshield’s sturdy construction, with a trapezoidal sheet enclosure, soon pays off in view of the high number of re-use cycles here, and the large units speed up repositioning operations.
In order to get the floor-slab formwork equipment up to the top storey of each tower quickly and easily, two wheeling-out platforms per tower were integrated into the Windshield system. The stripped formwork is transported onto these platforms and lifted from here by crane.
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During the winter months, the curing process after a slab has been poured is assisted by hot-air blowers placed under the floor formwork. By preventing heat escaping to the outside, the enclosure around the Windshield system has had a very positive impact here. Particularly with last winter’s low temperatures, this was especially advantageous and cost-saving.
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The Windshield system has done more than just enhance workplace safety, eliminate downtime and so speed up construction progress; also, a 9m stair tower integrated in the Windshield system enabled the site crew to walk up to the uppermost floor-slab in complete safety. This solution was used instead of the original plan for an up to 112 m tall stair tower to be erected beside the structure and which would have needed repeated vertical extensions to keep up with the progress of work. Here too, yet more equipment and labour costs were saved.
With the Doka systems, the construction project is right on schedule, and Viktor Mõisja, Head of the Concrete Construction Dept. at Estonian construction firm Merko, reckons that the structure shell will be completed as planned in the summer of this year.
“By deploying the Doka Windshield GCS, we have been able to carry out all floor-slab forming operations very safely and to speed up the construction sequence. Another advantage was that we were able to use one and the same safe system for the climbing formwork that we needed for the exterior walls,” said a visibly satisfied Viktor Mõisja, before adding by way of conclusion that “the Windshield system also saved us a lot of heat energy during the winter, of course”.
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| The Doka Windshield system permits fast cycle sequences coupled with safe working conditions, and minimises weather-related downtime. Only in this way was it possible for construction to progress so fast during the winter as well. |
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| The Windshield system from Doka enhances building-site safety and provides an improved working environment for the site crew. In order to get the floor-slab formwork equipment up to the top storey of each tower quickly and easily, two wheeling-out platforms per tower were integrated into the Windshield system. |
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