Concrete shells – Towards efficient structures: Construction of an ellipsoidal concrete shell in Switzerland

Concrete shells have been widely used in the past as economical and suitable solutions for a number of structures such as roofs, silos, cooling towers or offshore platforms. Taking advantage of their single or double curvature, bending moments and shear forces are limited and the structure develops mostly membrane (in-plane) forces, allowing to span large distances with limited thicknesses (typically of only some centimetres). In the last decades, the advances on numerical modelling, formwork erection and concrete technology open a new set of possibilities for use of concrete shells. In this paper, the design and construction of a shell with the form of an ellipsoid (93×52×22 m) and with variable thickness between 100 and 120 millimetres is described. The shell was built using sprayed concrete and also ordinary concrete in some regions. A number of tailored solutions were also adopted such as post-tensioning, addition of fibres and shear studs to ensure satisfactory performance both at serviceability and ultimate limit states.