Graphic Statics for the Structural Design of RC Wall-and-Slab Spatial Systems. The Example of the Retirement Home in Giornico, Switzerland

The Volta School in Basel, designed by the architects Miller & Maranta and the structural engineer Jürg Conzett in 2000, is the first built example of RC wall-and-slab spatial system. This system uses the horizontal stiffness of the floor slabs to support the load bearing walls eccentrically, thus allowing, if certain geometrical conditions are fulfilled, to change the position of the walls floor by floor. In this way the requirements of structural continuity is avoided, in favour of higher architectural freedom. The system presents some challenges in the construction phase and requires close collaboration between the architects and the engineers. This is the reason why there are very few buildings that use this structural system. One of the most recent examples of its application, designed by one of the authors, is the retirement home in Giornico. The design was performed using strut-and-tie and stress fields models, and it is presented in detail in this paper.