ABSTRACT
From load-carrying viewpoint, solar updraft towers are extremely enlarged, over-scaled natural draught cooling tower shells, showing all problems known to cooling tower designers (Harte & Krätzig 2002), as:
• high compressive stresses under Gravity load G, Wind action W and Temperature T ,
• tendency to vertical outside cracking under G, W and T ,
• high sensitivity to shell buckling instabilities under G, W and internal wind suction Wi,
• wind vibrations in the upper tower part, eventually leading to dynamic instabilities,
• a natural safety margin against seismic actions because of low 1st eigenfreqency,
• stress and thermal fatigue phenomena of the required high-performance concrete,
• durability problems to the end of life time. Numerical investigations have shown that the
hyperbolic shape with continuous curvature is favoring the load-carrying characteristic of such shell structures (Noh et al. 2012). Doubly curved hyperbolic shells with negative Gaussian curvature are able to resist loading mainly by in-plane extensional and shearing forces, the so-called membrane action. This principle must be adopted for solar updraft towers, if the intended service life-time of more than 80 years shall be achieved.
