Office building in Frankfurt

Building use

Office building

Country/Region

Germany

Overview

The building is the first mixed use building in downtown Frankfurt, introducing 147 residential units in an area of the city that is usually abandoned during the night and weekends. The architect developed a very distinctive silhouette for the building, characterized by a “hip-swing” at mid-height: the 8 residential floors (levels 15-22) are offset from the verticality of the office spaces above and below, creating the opportunity for open air terraces and overlooking views of the different units.

Basic information (construction date, number of stories, gross floor area, adopted design code, engineer(s), Contractor(s), etc.)

Construction date: 2016-2019
Number of stories: 46+4 below street level
Gross floor area: 54,100m2
Adopted design code: Eurocode
Engineer(s): PfeiferINTERPLAN – Bollinger + Grohmann
Contractor(s): Adolf Lupp GmbH + Co KG and FUCHS Europoles

Issue and/or innovation

The structural issue of the tower is given by the lack of verticality of the residential floors, that cause the structural columns to follow an unusual path creating strong horizontal forces that have to be transferred to the core by the floor slabs. Also, the lack of corner columns creates the need for long spans. The issue was due to the need of avoiding a transfer beam that would have occupied an entire floor.

Reason for composite solution

The composite detailing of the columns allowed the creation of the unique building shape without excessively large columns and without the need of a transfer beam. The circular spun-concrete columns that are present in all the office spaces change to rectangular-shaped inclined columns in the residential floors, to minimize their size and interference with the usable spaces of the apartment (columns are embedded in the partitions between the different rooms/units).

Specific solution/technical details

The lateral forces generated by the bended composite columns are transferred to the core through the concrete floor slabs, by using steel plinths embedded in the concrete floor slab. In the columns closer to the corners the forces where short-circuited one with the other by connecting two opposite columns by means of a steel tie, acting compositely with the floor slab. Spun-concrete columns are used for the other vertical floors of the tower.

Impact or effectiveness

The use of composite columns allowed the possibility to create the unique shape of this building without the need of transfer beams or other complicate structural solutions.