shell

In building construction, a shell structure is a thin, curved plate designed to efficiently transfer forces through compressive, tensile, and shear stresses within its surface. Typically made of concrete reinforced with steel mesh, this construction method emerged in the 1920s and became prominent for long-span structures after World War II.1

These structures can achieve significant spans, with thin parabolic shell vaults reaching up to 300 feet (90 meters). More complex forms, such as hyperbolic paraboloids (saddle shapes) and intersecting parabolic vaults, have also been created with very thin profiles, sometimes less than 0.5 inches (1.25 cm) thick. Notable designers in this field include Felix Candela and Pier Luigi Nervi.1