Formwork (debnenie)

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  • Datum přidání: 07. dubna 2007
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Formwork (debnenie)

Formwork is the key to successful an economic concrete construction. It has a dominant influence on the appearance and accuracy of finished concrete which in turn affects the ease with which the following trades can complete their work.

The types of formwork: - Wall- system-column- High quality column formwork forms concrete
Columns in next to no time: quickly folded for
Forming, and simply unfolded to strike, the
Formwork results in ultra-short cycle times. This Formwork can be moved in one piece with just one single crane movement. When collapsed, the panels can be easily transported and stored
-wall-simple to stack, flexible height and length
- Floor-system
- Self-Climbing-platform (SCP)-combination of wall and floor system,
-ideal for tall, slender structure and where ever large rises need to built on confined, cramped sites. The entire unit is lifted hydraulically in one piece.

Example of using the new formwork system
Making a modern landmark
Currently rising beside the Danube on Vienna’s “Handelskai”, the Millennium Tower will be(now is) Austria’s tallest building when it tops out at its planned height of 202 m. The 50- storey office tower is made in new self-climbing system.

The carcass is conventional reinforced concrete skeleton construction. The structural floors are 25 cm thick fair- faced flat floor slabs. The walls of the buiding core are made of standard B55-grade concrete. Various different construction methods are used for the building columns.In the entrance lobby, the columns are 8 m tall and 75 cm thick and are made of high strength B95 grade concrete, while on the floors above, the columns are 55 cm thick ant take the form either of steel composite columns or of high strength concrete columns depending on the loads encountered. Allowance had to be made here for the different types of column. After the complicated layouts of the basement storeys had been completed, the glass giant started to rise at the rate one storey of the week.
This unusual construction project called for an equally unusual formwork concept to match: the interoperation of Self-climbing platform for the building core, Automatic climbers for the façade, and floor formwork for the floor slabs.

After dismantling, this formwork was placed on the automatic climbers suspended from the outside of the structure ready to “hitch a ride” up to the next storey. By making it possible to pour walls and floor slabs in one piece, this novel combination gave rise to completely new working and pouring cycles.
Up to 29th floor, the quadratic floor-plan area of 28 x 28 m leaves all options open regarding the room layout. Right in the middle is the building-core(also quadratic) with lift and service shafts, lift foyers and a stairwell. Above the 29th floor, the core is only adjoined by floor on two sides which have a rather smaller quadratic floor plan measuring 22 x 22 m.

Fully automatic

This combination of the Platform SCP and the Automatic Climbers SKE(used for the first time here on the KolnTurm) was then developed in collaboration with the Formwork experts from Doka’s branch an the Automatic Climbing Team. While the self-climbing Platform SCP was used on the shaft core, the automatic climbers were used for forming the steel composite columns on the exterior of the building.
The self-climbing platform not only formed the entire shaft cross-section of the core, but at the same time carried all the formwork and all the working and storage areas. Powerful hydraulic cylinders shifted the entire unit in one single operation. All safety equipment and finishing platforms were lifted along with the work unit. Also used for the first time was the systematic nature of the Dokaflex floor formwork system. When this formwork was struck, it was placed on 2 m wide platforms on the automatic climbers of the external formwork so that it could move up to the next storey, while the quantity, weight and location can always be exactly specifed. Unlike normal climbing-formwork projects, pouring of the storey floors did not ‘trail behind’ construction of the core. Because the wall-formwork elements were suspended from the Doka Platform SCP, the walls and the floor –slab could be formed at the same time and poured one after the other, this doing away with the need for expensive, labour intensive reinforcement conections. One storey every week

A total of 850 m2 of large area formwork TOP 50 was suspended in the quadratic 17 x 17 m layout of the Doka Platform SCP. It only took the chief foreman, a push of a button and a two hour wait to lift the formwork one storey (3.37m), with the aid of six hydraulic cylinders.

Due to the continious platforms, the external formwork for the steel composite columns extended around all four sides of the structure and could either be raised all together, or on one side of the structure at a time, on the Doka Automatic Climbers, in exactly one hour. This resulted in a weekly cycle for the core and the floors with formwork being lifted on Monday, and reinforcement and formwork on Tuseday and Wednesday. On Thursday, pouring (with high-strength concrete) was carried out with formwork being struck on Friday. From the bottom to the top

From its first ‘climb’ from the concrete base-slab, the Doka Platform SCP was already in its assembled state, and continued to the 43rd floor without needing any further modifications( except that an additional outside scaffold was suspended on two of the sides from the 30th storey upward). Thereafter, the platform was easy to dismantle, even at a height of 148 m above the ground.
This enabled work to proceed exactly on schedule, leading to successful completion of the carcass in August 2000. Hochtief is currently continuing with the interior finishing work, seeing the structure through to completion on a ‘turnkey’ basis.
CEI 11/12 2000

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