Stricter standards in Copenhagen
Special challenges during the construction of a new metro station
Data & Facts
- Metro til Nordhavn station with viaduct, underground station and cut-and-cover tunnel
- PLM Architects Copenhagen, Arup, Rambøll Group
- Metroselskabet I/S, Kopenhagen
- MetNord Joint Venture
- (Züblin A/S and Hochtief AG)
- MEVA systems
- Engineering and support
- MEVA Schalungs-Systeme, Haiterbach
High expectations on architectural concrete
Construction of the Metro til Nordhavn station with a viaduct and a cut-and-cover tunnel in Copenhagen, Denmark, posed special challenges for the engineering team at the formwork specialist MEVA. Besides the demanding requirements that had to be met during this complex construction project, it also required extensive know-how and flexibility on the part of the engineering team from Haiterbach.
After a number of incidents had occurred during bridge construction projects in Denmark in the past, the Danish standard DS2427 was revised and the safety requirements tightened relative to the European standard EN 12812. Hence, all important details of the construction project with regard to the planning and execution as well as the approaches used for the structural calculation were agreed with all project stakeholders beforehand. “After submitting our first plans in November 2015 there were hardly any queries,” reported Jochen Stoß, who was responsible for the project in MEVA’s central application engineering department, and added: “We visited the site on a number of occasions to discuss the details with the responsible parties.” The high standards do, of course, come at a price: “Compared to similar construction projects we had almost twice as much planning effort,” summed up Jochen Stoß. MEVA delivered 127 plans in six months just for the planning of the 234-metre-long viaduct. The structural engineering involved in the project was also very demanding, according to Peter Hermann, who is responsible for structural engineering at MEVA: “The viaduct’s V-shaped supports for the subway tracks were to be poured in one cycle to avoid producing concrete joints.” In order to safely support and pour a component that can be up to 20 meters wide from below, the MEP shoring tower with special wooden formwork on top was designed like a set of pre-assembled tables, and of course, also met the stringent Danish standards.
High expectations on architectural concrete
The principal and the architects had high expectations with regard to the quality of the architectural concrete. A complete test pour was carried out using the MEVA formwork systems AluStar and StarTec just to get an impression of the planned quality of the concrete on the underside of the V-shaped supports of the subway viaduct. As the architects wanted to achieve a striking architectural concrete pattern, the formwork was covered with wooden shuttering panels. The principal was convinced by the result.
Another challenge was the installation of the shoring towers over an area of 4,000 square metres – on thick steel plates. The high horizontal loads that had to be taken into consideration due to the extremely low frictional resistance specified by the Danish standard could not be taken up by friction – an additional reinforcement was required. To a certain extent, the horizontal loads to be assumed for the MEVA MEP shoring towers according to DS2427 were twice those specified in EN 12812. “We produced an individual assembly plan for every single slab table,” explained Jochen Stoß. Due to the various base layouts, heights and slab thicknesses, the MEP shoring towers were able to effectively demonstrate their high degree of flexibility.
Cut-and-cover with 24-metre cycle lengths
The construction phase for the cut-and-cover tunnel was almost a home game for the MEVA engineers compared to the tasks involved in the metro station and the viaduct. Heights up to 4.75 metres over a length of 144 meters had to be formed using single-sided formwork, and, in addition, the slab formwork had to be installed. However, this structure also posed challenges: The floor and the roof were inclined in the longitudinal plane and the width was tapered in the plan view. “The absorption of the entire shear force caused by the roof played a central role for cycle lengths of about 24 meters,” recalls Peter Hermann. A substantial horizontal shear force is generated by a maximum gradient of 6% and a slab thickness of up to 90 cm. MEVA also had a solution at hand to deal with this: Using the STB 450 support frame, it was possible to support the enormous load pressure at the lower end of the formwork.
225 plans and 1,500 pages of structural calculations
In June 2017 the viaduct was completed with the portal frame. The pouring of the cut-and-cover tunnel, the metro station and one of the planned plant buildings under the viaduct is to be completed by April 2018 according to plan. No surprises are expected between now and then. All in all, and having supplied 225 construction plans and around 1,500 pages of structural calculations, Jochen Stoß and Peter Hermann have drawn a positive conclusion: “Despite the substantial planning and coordination efforts involved, the project always progressed smoothly and on time thanks to close consultation. In addition, this project allowed us to prove the value of our expertise and the advantages of our products.”