The daily newspaper “taz” Berlin has constructed a new publishing building on Friedrichstrasse in the centre of Berlin. This 7-level administration building has special structural features: The exterior frame of each slab (from the slab above the ground floor up to the slab above level 7) is formed by monolithic post-tensioning girders.
These monolithic girders were post-tensioned using post-tensioning tendons in oval ducts in accordance with ETA – 13/0839 approval. For static design reasons and for fire protection, common monostrand tendons could not be used in this case. Precast elements were placed in these frames, forming the slab.
The precast elements – ribbed slabs – were produced in a Polish precast concrete plant and were longitudinally post-tensioned using 162 tendons (length 11 m each) and 56 approx. 9 m long tendons.
Post-tensioning was carried out by DYWIDAG-Systems International Sp. z o.o., Poland.
Technical challenge: very limited space conditions
The technical challenge consisted in having to place, tension and grout the tendons in very limited space conditions. This resulted from the special design of the concrete supports that are X-shaped and are joined in steel joint connections. The tendons had to be placed through these joint connections. The crew only had two to three weeks per level to install, tension and grout the tendons.
Thanks to the efficient co-operation of the DSI units Germany and Poland, the 12 t of tendons were successfully installed within the given time frame.