Sustainable restoration of the roof of a large indoor pool

During an inspection of the roof of an indoor pool from 1971 in Potsdam (Germany) it was observed, that the roof and the column structures of the building are partially damaged by corrosion. The roof construction is a suspended simple-bent pre-stressed shell between two stiff edge beams. The span of the roof is 39.5 m. The edge beams are supported by A-frames. After further investigation on the damaged areas (including tension tests, tension tests on notched tendons with different load cycles, tests of the bearing capacity of sleeve splices and screw nuts) the conclusion was that the joint of the tension rod and the concrete column had to be restored. This was accomplished through the attaching of a new supporting construction to the existing parts, which took over the load from the old connection. At both sides of the columns pre-stressed DYWIDAG-single-tendons (St1080/1230, diameter of 36 mm) were used. They have to bear a maximal tension force of 835 kN. With this unusual restoration technique, a fast and relative inexpensive retrofitting of the construction could be carried out. The existing construction had to be modified only marginal, and the typical appearance of the building was preserved. This solution stands for sustainability.