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Positive, negative and zero Gaussian curvature of a shell

FROM:

Niladri Kanta, “Design of a thin concrete shell roof”, Master’s thesis, Delft University of Technology, June 2015

ABSTRACT: This master thesis involves the design of a roof for a basketball arena, which has a capacity of 20,000 spectators and it needs to be designed as a concrete shell structure. The size of the stadium is large enough to demand a long spanned shell structure. This thesis attempts to find an elegant solution to this problem, which combines aesthetic and structural beauty with efficiency during construction. These points are judged to be important aspects of a complete structural design. A literature study is done in an attempt to create a plan for the design of the shell roof. The general theory of shells is studied to understand their forms, structural behaviour and modes of failure. This helps the designer to understand the mechanics of shells which heavily influence the design procedure. Prominent shell designers of yesteryears and some of their projects are the next object of interest. Existing basketball arenas are also examined to find out the loading requirements for the roof in this thesis. The literature study is concluded by gathering details of high strength concrete and finite element software, both of which are relatively new in the shell industry. A design procedure is defined based on the findings of the studies mentioned above. The shell is chosen to be designed as a spherical dome. The initial geometrical details are stipulated after conducting sightline analysis, capacity calculations and hanging model analysis. Varying values of the span and thickness are chosen, leading to multiple design formulation, one of which is chosen based on a linear stability analysis. The selected design is then structurally investigated with inclusion of nonlinear effects and imperfections. The above mentioned process is executed using a combination of different softwares, for modelling, meshing and analyzing. Once the structural behaviour of has been verified, the stresses are checked and the design is finalized by defining the structural framework, and proposing the paneling and connection details.

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