Beim Bau des Roche Tower 2 in Basel, wurde mitunter mit dem Klettersystem Mac und der Wandschalung Mammut 350 gearbeitet.

High-precision work on a large scale

Every now and then, the youngsters tower over their older siblings. At present the Roche Tower Building 1 is the tallest office building in Switzerland. Its “younger brother”, the Roche Tower Building 2, is currently under construction and, when completed, will tower above its predecessor.

Data & Facts

  • Project
    Roche New Office Building 2, Basel (CHE)

  • Architects
    Herzog & de Meuron

  • Principal
    F. Hoffmann-La Roche AG

  • Contractor
    ARGE Marti Roche Bau 2 (Marti AG Basel and Marti AG Bauunternehmung Zürich)

  • MEVA-Systeme
    Mammut 350, MevaDecSTB 450, MEP, MAC, MGS

  • Engineering and support
    MEVA Schalungs-Systeme AG, Seon, Switzerland

Aufbau des Klettersystem MAC.

Planning and preparations for Switzerland’s tallest building

Every now and then, the youngsters tower over their older siblings. At present the Roche Tower Building 1 is the tallest office building in Switzerland. Its “younger brother”, the Roche Tower Building 2, is currently under construction and, when completed, will tower above its predecessor. 

With 50 overground storeys, the new building will reach a height of about 205 m and will thus be the first high-rise building in Switzerland above 200 m. At 30 m x 60 m, the floor area is significantly smaller than that of Building 1, while the new construction will be about 30 m higher. The new skyscraper will thus have a more slender appearance.

Convincing expertise
MEVA and Marti AG are trusted partners and have jointly taken on the task of planning and erecting the building shell together with the climbing formwork. The prestigious Swiss construction company already relied on high-quality formwork systems and professional expertise from MEVA during the construction work on Building 1. Thanks to the experience gained during this project, the MEVA engineers understood immediately which factors are important for the construction of Building 2 and were once again able to convince our long-standing partner with well-thought-out concepts and detailed planning. 

New challenges
Due to the logistical challenge of operating a large construction site in a central location, MEVA’s automatic climbing formwork was used for the construction of both buildings. Having successfully worked on two cores at the same time during the construction of Building 1, the decision was also made to erect the core of Building 2 using a similar method. “The core is split into two by a so-called lobby, allowing us to work with two climbing systems concurrently,” explains MEVA engineer Volker Götz, who is responsible for the project. “We thus gain an important time-saving benefit.” Of course, it was already necessary to plan the use of the entire formwork system in detail during the construction of Building 1 in order to meet the specified schedule for this large project. The fact that MEVA was again commissioned to do the new job also reflects that the first job was completed successfully and that all participants were satisfied with the execution of the construction work. The formwork experts now had to exploit the experience gained and use it to master new and different construction challenges. 

Under the tower
First of all, three basement levels were built in a 20-meter-deep construction pit. After the first excavation phase, a floor slab with a ring-shaped opening was poured at the height of the second basement level. This so-called bracing slab subsequently served to reinforce the construction pit. The third basement level was then constructed using the cut-and-cover method. The excavation of the underlying third level was prepared by installing a number of steel supports via bored piles. During the work in the third basement level the ring-shaped bracing slab was supported by these steel supports. 

Preparations in the third basement level
To prepare the building cores, first of all an elevator pit was integrated into the 2.5-meter-thick floor slab at the third basement level. The integration of the shafts means that the slab is 4.25 metres thick in this area. In order to create the space required to subsequently install the lifts, the geometry of the cores had to be precisely taken into consideration. At the same time, delivery of the support frames as well as the Mammut 350 wall formwork began. 

Manoeuvring in cramped pit
The construction of the 7.9-meter-high walls was planned using the STB 450 support frame. In conjunction with the large-format Mammut 350 wall formwork it was possible to achieve the desired height with just two height extensions. As the outer walls were located below the bracing slab and it was not possible to move the formwork by crane, mobile support frames were used. However, the above-mentioned steel supports meant that they was only limited room to manoeuvre. The STB 450 support frame stands out due to its low depth of only 2.45 m and thus saves a lot of space on the construction site. The construction becomes slightly wider due to the use of trolleys. To make optimum manoeuvring possible in the restricted space in the construction pit, MEVA used new trolleys located closer to the formwork. “That really was high-precision work on a large scale,” said foreman Armin Looser. “The MEVA engineers had taken all factors into account and also considered the implementation so that we were able to work here without problems.” It was thus possible to pour cycles with a length of about 10 metres below the bracing slab. To do this, four filling nozzles were used per cycle. The team at the construction site then compacted the concrete using external vibrators powered by compressed air. 

External anchoring
Upon completion of the outer walls of the third basement level, the steel supports had to be encased. The reinforced-concrete composite columns with a floor area of up to one square metre were also formed using the Mammut 350 wall formwork. Due to the internal steel supports the decision was made to connect the formwork over the outer edges with alignment rails and column brackets. 

New dimensions
It was, however, possible to form the two building cores up to a height of 3.80 m conventionally using Mammut 350 formwork. Here the labyrinthine geometry of the numerous shafts had to be taken into consideration, as besides three stairwells and a total of 16 lifts, the building cores also house various supply shafts. With new planning instruments, the MEVA formwork engineers used a simple and precise solution to create detailed formwork plans. which were mainly drawn in 3D to help all the participants better understand them. This enables complex factors in the formwork planning to be better depicted spatially. The construction phases can be presented realistically and viewed from different perspectives. For example, when forming a T connection in the wall formwork, it is not possible to use the top tie position, making it necessary to stabilise the formwork with alignment rails. The use of comparatively small system parts such as tie rods and alignment rails is hence exactly planned to prevent deflection, for example. The advantage of a 3D model is that it is possible to create 2D plans and bills of material at the push of a button. “Especially for cores with 2,200 m² of formwork, this makes things a lot easier for our engineers,” Volker Götz is happy to say. “We work very precisely and efficiently. Our customers profit directly from this as the plans can be created quickly, and changes are also easier to implement.” Thanks to these 3D views the staff at F. Hoffmann-La Roche AG were able to get an exact picture of the construction work on their building without needing expert knowledge of formwork engineering. Hence, the comprehensive planning work not only helps to ensure smooth construction progress, but also improves communication between the parties involved.

Bespoke climbing system
Finally, the automatic MAC climbing system has to be precisely installed on the conventionally formed layout of the cores. As the system (including the hydraulics) is planned individually for each application, the MEVA staff had already prepared the MAC for the major application in the factory. About 100 platforms were specifically tailored to meet the requirements of the Roche Tower Building 2. It was necessary to produce the beams and cylinders to the desired dimensions so that they could be assembled on-site without a hitch. MEVA offers this service in order to make use of the complex climbing formwork as easy and efficient as possible for the customers. The installation of the MAC climbing system at the construction site was completed in only four weeks.

Clever logistics
On average, almost two lorries a day left the MEVA headquarters in Haiterbach to deliver the automatic climbing system. Thanks to the exact preparations it was possible to lift the pre-assembled platforms directly from the lorries upon arrival in Basel. This enabled the MAC to be installed directly without taking up valuable space in the construction pit for interim storage. “The team on the construction site was already familiar with the MEVA systems,” said foreman Armin Looser. “A large proportion of the team had already been involved in the construction of Building 1 and was familiar with the assembly processes. This means that we have no idle times and also that the set-up and the use of the MAC was no trouble at all thanks to the support provided by MEVA.” 

Flexible slab formwork
The climbing system was already put into operation at the third basement level and passed through the opening in the bracing slab. This then had to be closed without delay. Due to the height of 8.5 metres, Marti AG relied on the modular MEP shoring tower system to support the slab formwork. With diagonal cross-braces, the system (including the flexible MevaDec slab formwork) was adapted to fit the required surfaces. In those areas where the prop spacing does not match the dimensions of the MEP frame due to the changing orientation of the main beams, the diagonal cross-brace provides the necessary rigidity. The plug-in drop head enabled the MevaDec slab formwork to be used quickly and simply, whether from above with corresponding fall protection equipment or from below from the working platform of the MEP shoring tower. At the same time, the MevaDec drop head allowed for early stripping by lowering the primary and secondary beams of the standard slab formwork by 19 cm. Being able to reuse the slab formwork earlier enables the material stock to be optimised. 

Climbing out of the ground
At the second basement level it was possible to move the support frames by crane as the slab above had not yet been poured. The outer walls at the first basement level were formed using double-sided formwork before the construction pit was subsequently filled in. The new high-rise building will start to slowly grow out of the ground in January 2019. The MGS guided screen system and the MAC with closed working platforms ensure the highest level of safety. 

Read more about the progress of the construction work in the next issue of FormworkPress!

Schalungen in kombination mit Stützbock und Bewehrungen im Hintergrund.
Technische Abbildung von Wandschalung Mammut 350 mit Sicherheitssystem.
Zeichnung von Betoniervorgang mit Wandschalung Mammut 350 mit Sicherheitssystem.