The New Henninger Tower - Thermally separated balconies

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Project: New Henninger Tower

Products used: HALFEN HIT Insulated connections

City: Frankfurt, Germany 

About the Henniger Tower Project

Building land is becoming increasingly scarce. That is one of the reasons why our cities continue to grow in height: to provide more office space, and to create more apartments for the residential segment. The newly built Henninger Tower in Frankfurt sets new standards in this respect.  
Its façade is characterized by balconies and conservatories, whose low thermal bridge fastening was realized with Halfen insulated connections from Leviat. The technical office staff of the Langenfeld fastening specialists was involved in an advisory capacity in the implementation planning by the responsible structural engineer. Among other things, they provided support for the unusual panel geometries.

At 140 m high, the new Henninger Tower is one of the tallest residential buildings in Germany. Its architecture is based on the design of the Henninger Brewery, which was demolished in 2008 and helped shape the city's skyline for decades. With 207 exclusive flats on 40 floors, the building is in line with modern trends: Germany's metropolises have rediscovered high-rise residential buildings and want to avoid the mistakes of earlier large housing estates, which today often struggle with anonymity and social problems. Thus, the 19,000 m2 of pure living space in the Henninger Tower is aimed at an affluent clientele.  
In addition to the luxurious condominiums with concierge service, there are also available shops and a supermarket. A restaurant designed exclusively for the viewing platform will enrich the south of Frankfurt with a culinary attraction of the highest standard. Around the tower, a U-shaped perimeter block development will provide additional residential and commercial space. 

Flats with outdoor areas are a possible reality

The architects Meixner Schlüter Wendt from Frankfurt describe living in the new Henninger Tower as a "residential landscape", in which balconies provide outdoor areas for the flats.  
These balcony and terrace levels, as well as attached winter gardens, form transition zones between sheltered interior and exterior spaces with views of the city. The supporting structure for the new Frankfurt landmark was designed by EHS beratende Ingenieure für Bauwesen GmbH from Lohfelden. The structural engineers brought Leviat's technical office on board for the low thermal bridge and economical construction of the design-defining balcony slabs.

Leviat’s technical office helped from the initial stages of the project

The ground plan of the tower is rectangular. Up to the 30th floor, the dimensions of the building are 27 m x 38 m. Above this, eccentrically arranged, there are a further six rounds of floors, which, as with the old Henninger Tower, form the so-called "barrel".  

Bracing is provided by a reinforced concrete core, by the perforated façade arranged on the north side, and by an outrigger system with a total of four massive panes. The outer edge of the "barrel" above rests on four reinforced concrete wall elements projecting from the core. Moderately prestressed reinforced concrete flat slabs with a span of 8.50 m were used for the Henninger Tower. Due to its complex nature, the EHS engineers made use of the expertise of Leviat's technical office staff from the initial stages.  
This was a complex project especially because of the iso-element dimensioning. As such, Leviat’s technical experts provided support and advice for the challenging connection situations.  
By establishing contact at an early stage, it was possible to jointly work out the best and most economical solutions for all parties involved. Get in touch if you too need help from our technical support team.  

Technical details about the HALFEN HIT Insulated connections used in this project

Leviat’s HALFEN HIT Insulated connections are particularly suitable for high-rise projects such as the Henninger Tower.  
They have the standard fire protection properties REI120 according to DIN EN 13501 and F120-AB according to DIN 4102. This means that load-bearing capacity, room-enclosing functions, and fire protection are maintained for at least 120 minutes in the event of a fire.

The HALFEN HIT-HP and HIT-SP insulating elements use non-combustible mineral wool of fire protection class A1 in combination with the special shape of the insulating body. A stable plastic box, which is flame-retardant according to Z-15.7-364, protects the mineral wool and fixes the load bearings.

With a reduced tension rod cross-section, reduced penetration points and the continuous insulation material, thermal bridges are efficiently reduced. HIT insulated connections allow relative deformation of the connecting component to the building, thus enabling thermal expansion without cracking. Leviat offers this solution for many applications, including simple symmetrical connection elements for cantilever balconies, corner solutions, or for height offset connections, for example for plinth formation. The system has a European Technical Assessment (ETA) as well as general building authority approvals (abZ) and, thus, offers a high degree of planning security. In addition to the design model and further design information, the thermal bridge parameters ((y, qmin und fRsi) are included in the abZ's as well as the impact sound level difference values (DLn,W) in the ETA and abZ's.

Tremendous load peaks at the corner of the building  

Leviat provides the HIT planning software for design and waste optimisation. But in the case of the Henninger Tower, the application reached its limits. Due to the corner design of the cantilever slabs, enormous load peaks are concentrated at the corner of the building on the structural side. Finally, the dead weight of the slabs in the Henninger Tower, due to their massiveness with calculated thicknesses of up to 40 cm (about 1.31 ft), resulted in enormous effects.

We developed a special solution for our client

Our technical experts examined the connection situation of these corner plates through an intensive FEM analysis. On this basis, the required insulating elements could be pre-dimensioned, also under the aspect of economic efficiency, and implemented together with the responsible structural engineers. We then manufactured the elements specifically for the Henninger Tower, particularly in the distorting beams. Finally, the geometry of the insulated connections was adapted to the planned reinforcement layout of the execution planning in such a way that iron collisions on site and construction delays could be prevented. 

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