Twisted highrise architecture from Zaha Hadid

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Il Dritto (The Straight One), Lo Storto (The Twisted One) and Il Curvo (The Curved One) – the names given to the three skyscrapers at Milan's Piazza Tre Torri, the core of the ambitious CityLife urban development project. Lo Storto, The Twisted One, is the future administrative building of the Generali Insurance Group. The 44 floors of the 170 m high-rise office building gracefully wind their way upwards. It was designed by the recently deceased star architect, Zaha Hadid. Likewise part of the CityLife project, the Hadid Residences also feature her distinctive style and clear design language.

The concrete shell of the striking Generali Towers was completed in April 2016 – after a construction phase of only 17 months. With the help of project-specific PERI formwork operations, it was possible to finish ahead of the originally planned schedule by a full 3 months. This was because the formwork and scaffolding specialists at PERI Italy developed an execution solution with consistently safe and thereby fast operating sequences. In spite of the complicated building geometry, the standard stories could be realized in continuous weekly cycles.

One climbing system as protection panel and climbing formwork

The PERI project solution was based in particular on the RCS Rail Climbing System. On the one hand, this was used as a climbing protection panel for the top floors under construction at any one time. In addition, the RCS system served as climbing formwork for the building's core. Through the rail-guided climbing operations, the climbing units were securely connected to the building at all times which ensured the climbing procedure was always carried out quickly and safely even during windy conditions. By means of mobile climbing hydraulics, the units could be lifted to the next section each time without requiring a crane.

Climbing combination for the core

The floor slabs revolve around the centrally positioned core of the high-rise building whose complicated ground plan geometry is composed of circular and angular external walls as well as contrasting slender internal walls. Furthermore, the external walls of the core taper in 15 cm increments from a massive 90 cm at the base to a much thinner 30 cm in the upper floors.

The PERI climbing formwork solution was based largely on the crane-independent working RCS Rail Climbing System, combined with a self-climbing ACS Platform Unit along with crane-climbed CB Climbing Platforms and BR Shaft Platforms. With the help of the ACS technology, the placing boom could also be guided upwards. The reinforced concrete walls were formed accordingly using TRIO Panel Formwork and VARIO Girder Wall Formwork, supplemented by project-specific special formwork elements.

Maximum safety and fast shuttering times

The RCS P Climbing Protection Panel secured the leading edges of the twistedly-arranged floors so that the walls, columns and slabs could be safely formed at all times. In addition, the increased feeling of safety – due to the gap-free enclosure – accelerated the construction progress ensuring that forming operations could continue throughout independent of wind and weather.

For realizing the 32 cm thick floor slabs, SKYDECK Panel Slab Formwork complete with the drophead system was used. In the process, fast shuttering times with short striking times were achieved. Problem-free adaptation to suit the slab geometry which changed from storey to storey as well as shuttering the columns was carried out by means of standard compensation elements.

PROKIT anti-fall protection usefully supplemented the PERI execution solution and consistently implemented the safety concept in all floors for all shell construction operations and finishing work. With side mesh barriers, posts and slab feet, flexible use without any additional planning effort for accommodating the complex building geometry also proved to be unproblematic.