Filigree reinforced concrete net shapes and supports office tower

August 3, 2011 | Prosta Tower, Warsaw, Poland
Situated in the Warsaw city centre, the Prosta Tower features a very striking concrete and glass facade complete with a superb architectural concrete finish. With the help of a comprehensive formwork and scaffolding solution designed to match the high requirements, the construction team required only 11 months for the structural work.

The downtown area of the Polish capital of Warsaw has a new architectural highlight. It´s not the 70 m height and shape that makes the Prosta Tower unique – it is the front of the building consisting of glass and a reinforced concrete structure comprising individual diamond-shaped sections in a perfect architectural concrete finish that characterizes the appearance of the office block. The delicate, forward and reverse-inclined concrete facade has been installed in the form of a net over the external glazing – in addition, it serves as a structural component.

Architectural and logistical challenges
The challenges for the Warbud construction team on the one hand included ensuring that the form of the complicated concrete structure was accurately realised in spite of the high degree of reinforcement as well as having to take into consideration a formwork pressure of 90 kN/m² – as well as achieving a perfect surface finish with no tie points. On the other hand, the inner-city location with no available storage space as well as the resulting site facilities with only one crane, meant that detailed site logistics operations were required to suit the construction progress. Furthermore, the floor plans along with the cross-section of the reinforced concrete structure changed repeatedly from floor to floor.

Well-matched
In close consultation with the site management, PERI´s Polish engineers designed a comprehensive formwork and scaffolding solution tailored exactly to match all requirements. By means of test assemblies for constructing reference structures, the architectural concrete team coordinated the detailed combination of formwork, scaffold and concrete technology in advance. This resulted in optimised results and led to accelerated construction progress without any detrimental impacts which meant subsequent surface treatment could therefore be avoided.

Special formwork from system components
For constructing the reinforced concrete facade, the TRIO panel formwork served as an inexpensive as well as a simple and quick to assemble basic form with a formworking height of 3.60 m. Double-layered formlining provided attractive and virtually joint-free concrete surfaces; for this, Fin-Ply Maxi formliners were the preferred choice. Due to the special panel arrangement as well as the use of load-distributing compensation walers, the tie arrangement could be determined so that anchoring did not have to take place through the concrete itself.

For millimetre-exact shaping of the structure, project-specific box outs were used. The basis for this was formed by rentable system components such as steel walers, heavy-duty spindles and standardised connecting means – all taken from the extensive PERI product portfolio. The special formwork elements were completely pre-assembled at the PERI formwork assembly hall in Warsaw and subsequently delivered ready-to-use to the job site. All the in total 28 elements required for the standard and special cross-sections were equipped with a specially-designed striking mechanism. As a result, striking could be carried out without any damage to the formwork and concrete structure. In addition, the PERI concept for the internal formwork took into consideration the massive reinforcement connections at the height of the floor slabs.

Formwork + scaffolding = complete solution
A continuously extended working scaffold in line with the building progress on the basis of the PERI UP Rosett modular scaffolding system supplemented the PERI complete solution. This greatly contributed to maintaining the construction schedule as well as increasing safety levels for site personnel. The scaffold construction fulfilled two purposes here: it served as a supporting structure for the respective topmost working level with sufficient space available for forming, reinforcement work and concreting operations as well as facade scaffolding for the subsequent assembly work. Bracket extensions on the inside allowed maximum adaptation to the facade structure and through this guaranteed optimal and safe accessibility.

Prosta: not the easiest of tasks
The name of the 24-storey office complex – "Prosta Tower" – with over 8,000 m² of high-quality working space is derived from the street of the same name: the Prosta Street in downtown Warsaw. The translation for the Polish word "Prosta" is "straightforward" or "simple" but is not necessarily true when referring to the new structure. On the contrary, implementation of the architectural requirements was extremely demanding and the building with the filigree reinforced concrete web seems anything but straightforward and simple.

Contractor: Warbud S.A., Warsaw
Field Service: PERI Warsaw, Poland

PERI Systems In Use:
- TRIO panel wall formwork
- PERI UP Rosett modular scaffold
- Fin-Ply Maxi playwood

PERI was founded in 1969 and is today the leading provider of formwork and scaffolding systems. Along with the headquarters in Weissenhorn, Germany, the company has 48 international subsidiaries and 100 stock yards around the world. The company has over 5500 employees. 2010 revenues was 825 million Euros.

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This release was published on openPR.