Construction of the new GAP 15 office building in Düsseldorf, in which the existing north facing façade is to be retained for building preservation reasons and will be integrated in the new building.
The high-rise part of the building (24 upper storeys) will be built as a steel skeleton structure with a stiffening core. The flat ceilings will be borne by 4 interior columns and 35 external columns, the stiffening elements are two coupled cores.
The appendant low building (5 upper storeys) will be built using a stiffened reinforced concrete structure with flat ceilings.
The basement storeys will be built with a cover and cut construction method.Country:

Construction:
- Primary columns with slotted lamellae
- Curtain walls
- Cover and cut construction above 2nd floor basement
- Upward construction
- Two-storey excavation
- Downward construction
- Installation of a shallow, spread foundation with connection to the primary columns and slotted lamellae

Country:
Germany, Federal State of Nordrhein-Westfalen

Client:
GAP 15 GmbH, Duesseldorf

Planning period:
2003-2005

Costs:
30 million Euro

Services:
- Determination of the structural concept under constructive and economic aspects
- Structural design; preliminary, con-ceptual and appro-val stage design