ABSTRACT
This chapter looks at different ways that shells can be defined: Regular geometry, curved surfaces generated from ruled surfaces, mathematical models of double-curvature, physical models of hanging fabric, or even digital modeling techniques. It explores how each method evolved and how the relationship between structural form and construction shaped the ingenuity, economy, and evolution of shell structures. Structural shells, or surface-resistant structures, are three-dimensional load-bearing surfaces made from thin and stiff materials designed to resist external loads through their membrane. Concrete is the traditional material of choice for shells because it can be cast into different forms, it’s inherently stiff, and it behaves monolithically as a compressed bearing surface. Matching form to forces with a curved and stiff surface material are shells’ mandatory conditions. The most decisive influence on a shell’s effectiveness is the combination of material behavior and the form of the curved surfaces.
