Flexible tower construction

The Goal

To build the tallest office building in Switzerland safely and efficiently
With a height of 205 metres and 50 storeys, the Roche Tower Building 2 would be the tallest office building in Switzerland once completed. The contractor wanted to build on the lessons learned from the previous building, Roche Tower Building 1, to ensure that this tower was built even more efficiently and safely.

The Project

Summary:

The graduated taper of the building meant that the complex formwork operations required thorough preparation to ensure the work was safe and could be delivered efficiently.

Challenge:

The shape of the building meant that the building’s core shafts had complicated geometry that needed careful planning. In addition, the height of the building presented safety concerns. 

The central location of the buildings within a built-up area was a further challenge, as space was limited for planning construction activities. For example, the formwork would not be able to be moved using a crane for the excavation works or for the building construction.

The Solution

1. Early Collaboration for Efficient Solutions

   Having worked together on Roche Tower Building 1, MEVA and Marti AG built on that experience by undertaking the formwork planning at an early stage.

   The MEVA engineers immediately understood what was important when erecting the second tower and used tried-and-tested concepts combined with detailed planning. By collaborating during the design, the potential problems – such as the basement excavation and the complicated core geometry – were identified and resolved prior to construction.

   The chosen solutions used the strengths of STB 450 support frames, as well as the MEVA Automatic Climbing (MAC) system combined with Mammut 350 wall formwork and MGS-H screen system, to deliver the concrete works.

2. Solutions for Confined Conditions
   The initial excavations for the three basement levels included a 20-metre-deep excavation, which required bracing. In addition, the crane would not be available to move formwork for the basement walls, so the process needed to be determined in advance.

   After the bracing slab with a ring-shaped opening was poured, the construction of the walls below was planned using the STB 450 support frame. As it was not possible to move the formwork using a crane, mobile support frames were used in the confined conditions of the basement excavation.

   

    

3. Enhanced Efficiency with the MAC
    
   a) Two-system design for the split core
   Due to the logistical challenge of operating a large construction site in a central location, automatic climbing formwork was used for the construction of the split building cores. 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. 

   Because the core is split into two by a lobby, the MEVA engineers proposed that two climbing systems could be used concurrently. This would provide a significant time advantage, as well as providing a safe working area for the site staff.

   b) Precise planning for complex geometry
   The walls of the two cores were poured up to a height of 3.8 metres using the Mammut 350 wall formwork. However, to ensure that there were no issues due to the complicated geometry of the numerous shafts, the cores were drawn in three dimensions. With the 3D model, it was then possible to depict the construction phases spatially in order to more precisely plan important details.

   c) A bespoke system tailored to the project needs
   The pour cycles and hydraulics of the two MAC systems were planned individually. To ensure that the set-up on site progressed smoothly, the relevant system parts were planned and delivered in the bespoke dimensions required for this project. This way, the installation of the systems onto the cores was more efficient. 

   In addition, during the course of the construction work, the contractor suggested additional ways to optimise the process which would further accelerate the programme and save money. MEVA worked with the professionals from Marti AG to design and implement their ideas.

   

   d) Innovative transportation solutions
   In order to place the prefabricated staircases in the shafts during the construction work, the MAC was equipped with hinged hatches in the platforms. The prefabricated parts were lowered through the climbing system into the shafts using a crane. A crane runway attached beneath the MAC by MEVA then enabled the components to be moved precisely in the shaft without tying up expensive crane time.

4. Safety as a Top Priority
   Safety was an important aspect throughout this construction project, which required flexible solutions to ensure it could be achieved. The rail-guided MGS screen system offers comprehensive all-round protection when working at great heights. However, the floor plan became progressively smaller above the 14th floor. On the north side of the building, the slabs are set back by 2.90 metres. This process is repeated every three storeys.
   

   The required conversion of MAC and MGS was planned in detail by MEVA in order to make the work easier and safer. The systems were designed so that the individual components can be removed as a single unit and quickly disassembled. The safety concepts developed by MEVA and Marti formed the basis for detailed work instructions. This enabled the construction work on Roche Tower Building 2 to be planned and executed step-by-step in safe work cycles.

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The Outcome

Thanks to the strong working partnership between MEVA and Marti AG and the early collaboration this enabled, the building structure was completed ahead of schedule in December 2020.

Featured Products

• Mammut 350 wall formwork
• Support frame STB
• MEVA Automated Climbing (MAC) system
• Screen System MGS-H

Client:
ARGE Marti Roche Bau 2 (Marti AG Zurich/Basel)

Project:
Roche New Office Building 2

Location:
Basel, Switzerland

Principal:
Hoffmann-La Roche AG

Engineering & Support:
MEVA Schalungs-Systeme AG, Seon, Switzerland and MEVA Schalungs-­Systeme GmbH, Haiterbach, Germany