Alster Swimming Pool in Hamburg
- Heide Wessely
The Alster Swimming Pool, a symbol of Hamburg’s postwar modernist architecture, is one of Europe’s largest shell constructions and an engineering masterpiece. The concrete of the hyperbolic paraboloid shells spanning up to 96 m is only 8 cm thick. The roof covers an area of 4500 m². Only three column supports transfer the loads of the self-supporting structure into the bedrock. A concrete tension member stabilises the two outer columns. Modernising and intervening in this sensitive system built in 1973 was no simple task. Digital tools contributed to the success of the project in a significant way: 3D modelling, software for planning building services, calculating building material quantities based on 3D illustrations, and point cloud surveys. Complete drawings of the existing conditions were no longer available. Interventions in the complex geometrical form and its filigree construction components were to be as minimal as possible. The shell roof is historically listed, just as the 10 m tall diving platform and the facade. Its aluminium triple chord columns were carefully tilted outward from under the roof, retrofit in the workshop, and built back into the structure. In the area of the upper connection, the planners also retrofit the existing telescoping cylinder support, which can absorb the vibrations in the roof surface. Contemporary triple glazing would have been too heavy for the existing columns. This is why the facade only features double glazing.
