High-rise development at the Münchner Tor
Sharp-edged, elegant and visible from a long distance – two slim, glazed, high-rise slabs transform the skyline in the north of Munich: 113 and 126 metres high, they demarcate the newly built quarter, Parkstadt Schwabing, in the periphery of the Mittleren Rings directly at the T-junction to the A9. This bold architecture of the HighLight Towers is thanks to Chicago architect Helmut Jahn. The complex consists of two high-rise buildings, supplemented by a 5-storey office and business centre along the Schenkendorfstraße and a 7-storey hotel complex in the northern part of the property. “Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away”, according to Helmut Jahn, who sees plenty of scope for innovations in architecture.
Efficient high-rise architecture
The HighLight Towers planned by the team Murphy / Jahn are proof: design, structure and construction of the high-rises are tailored to utmost efficiency. Alongside the high aesthetic requirements, the concept is also committed to tackling the utmost objectives in engineering skill – the minimization of construction areas. The two towers are designed as reinforced concrete structures with vertical steel framework bracings for support. Following the requirement of airiness and flexibility, the internal finishing was executed throughout in dry construction – using Knauf systems. The highly sophisticated structures and detailed solutions in terms of civil engineering physics and fire protection technology are the result of an intensive cooperation between the architects, STRABAG as the general contractor, Knauf, and the ARGE dry construction – documented in a detailed catalogue with more than one hundred solutions. By involving Knauf in the planning process early on, it was possible to optimise a whole host of ideas.
Architecture and energy concept
In the ground plan, the thin, offset parallelogram towers are set apart from each other at a distance of 22 metres. They take the shape of a parallelogram with an overall length of approx. 73 metres, a width of 13.5 metres and a floor area of around 1.000 square metres. B1 refers to the taller tower comprising 32 floors; B2 the shorter one with 28 floors. Bridges, so-called “clip-on elements”, create a flexible connection between the two. If necessary, they can be added or removed, and enable up to 2.000 square metres of office renting spaces per floor. Although three bridges were originally intended, a total of eight are structurally feasible. The glazed lift towers are situated opposite each other and indicate the entrances to both tower blocks at the central plaza.
The facade has been chosen whilst taking into consideration technological and ecological facets. It has been designed in direct conjunction with the efficient ventilation and air-conditioning systems of the tower blocks. Thereby, openable window structures allow employees personal ventilation and the required proximity to nature. This is achieved using a single-shell curtain wall with heat-reflecting glazing as well as a window structure incorporating wind protection and sound-insulating elements.
Innovative supporting structure
A special feature of the design is the supporting structure which is of a simple steel composite construction. A characteristic of this type of structure is its considerable slenderness coupled with a minimized loss of construction area. Both the cross-sections of the framework elements and the supports are made of solid steel, which is housed in a jacket pipe and then filled with concrete; achieving a fire protection requirement of F120. Lean supports, 28-centimetre-thick cast-in-situ ceilings as well as the arrangement of two vertical framework structures for each tower comply with the Munich architects´ requirements of maximum transparency. This type of structure also enables a speedy installation: It was possible to erect one floor for each tower per week. Due to the arrangement and form of the load-bearing cores, which in the ground plan extend as an open U across the entire width of the building and are located in each case at both ends of the building, a considerable flexibility was achieved in the floor-plan composition. The Murphy / Jahn concept intends for two options that offer entirely transparent levels: the design for two or for one tenant.
Perfected dry construction In conjunction with modern, efficient dry construction, the advantages of the steel composite construction were used effectively and in a target-orientated manner in the tower block structure. The significant demands concerning fire protection and sound insulation, and the specific features of the structure, played a major role in determining the dry construction of the HighLight Towers In intensive collaboration with Knauf, optimised solutions were developed based on existing systems. It was also a matter of developing bespoke solutions adapted to the architecture and of officially licensing these by means of test certificates.
The most important wall in the dry construction is the Knauf Fire Wall system, W131, which flows concentrically through both of the towers. This divides the building into two 400-square-metre fire compartments. The planning had the task of solving practical details, like the penetration depths of the wall in the area of the stairs, connections of the fire walls at the diagonals of the framework structures or at the round columns as well as on the facade. As building movement was expected – the specific deflection of ceilings under load totals around 16 millimetres – the main part of the connections had to be designed so they could move.
Murphy / Jahn also placed considerable demands on the execution. The specified DIN tolerances for the dry construction are not accepted in Munich. This is why Knauf´s V-milling technology posed an attractive option. It enables the necessary exact precision coupled with efficient installation.
It took two weeks to execute the basic dry construction installation for each floor. After concluding the installations, a follow-up of one and a half weeks was required.
The integrative cooperation in an early planning phase was an important foundation for the on-site architects, Murphy / Jahn, for being able to achieve the considerable aesthetic and structural level in dry construction. The slender structure could only be realised using this dry construction. It was therefore very important for us to manage the detailed plan directly with the manufacturer and the executing company right from the start.
Under-floor lines accessible at any time
As the offices of the two towers have an enormous installation volume of building, air-conditioning, ventilation, EDP and communication technology, a raised floor on steel supports at increments of 60 x 60 cm with a structure height of 320 mm was laid. The under-floor lines can be accessed at any time and from any point, as you can remove individual elements of the floor and then install them again. The floor thus offers the greatest possible flexibility for maintenance work and also any later changes of use. Knauf Integral and Mero TSK International took just 12 months to manufacture and install all the floor surfaces using Mero type 6N36 on Knauf Integral GIFAfloor basis. It was possible to load the raised floor just 24 hours after installation. This means the construction process was not hampered in any way, which would have been the case, for example, if wet-laid cavity floor systems had been used. The raised floor is also perfectly suitable for taking loose-lay textile tiles, providing considerable flexibility for any tenant and use changes.