A shell is a three-dimensional solid

structural element In structural engineering, structural elements are used in structural analysis to split a complex structure into simple elements (each bearing a structural load). Within a structure, an element cannot be broken down (decomposed) into parts of dif ...

whose thickness is very small compared to its other dimensions. It is characterized in structural terms by mid-plane stress which is both coplanar and normal to the surface. A shell can be derived from a plate in two steps: by initially forming the middle surface as a singly or doubly curved surface, then by applying loads which are coplanar to the plate's plane thus generating significant stresses. Materials range from concrete (a '' concrete shell'') to fabric (as in '' fabric structures''). Thin-shell structures (also called plate and shell structures) are lightweight constructions using shell elements. These elements, typically curved, are assembled to make large structures. Typical applications include aircraft

fuselage The fuselage (; from the French language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...

s, boat hulls, and the

roof A roof (: roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of tempera ...

s of large buildings.

Definition

A thin shell is defined as a shell with a thickness which is small compared to its other dimensions and in which deformations are not large compared to thickness. A primary difference between a shell structure and a plate structure is that, in the unstressed state, the shell structure has curvature as opposed to the plates structure which is flat.

Membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...

action in a shell is primarily caused by in-plane forces ( plane stress), but there may be secondary forces resulting from flexural deformations. Where a flat plate acts similar to a beam with bending and

shear stress Shear stress (often denoted by , Greek alphabet, Greek: tau) is the component of stress (physics), stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross secti ...

es, shells are analogous to a cable which resists loads through tensile stresses. The ideal thin shell must be capable of developing both tension and compression.

Types

The most popular types of thin-shell structures are: * Concrete shell structures, often cast as a monolithic dome or stressed ribbon bridge or saddle roof * Lattice shell structures, also called gridshell structures, often in the form of a

geodesic dome A geodesic dome is a hemispherical thin-shell structure (lattice-shell) based on a geodesic polyhedron. The rigid triangular elements of the dome distribute stress throughout the structure, making geodesic domes able to withstand very heavy ...

or a hyperboloid structure * Membrane structures, which include fabric structures and other tensile structures, cable domes, and pneumatic structures.

References

External links

Thin-shell structures

Double thin-shells structures

Hypar & Concrete Shells

Past and Future of Grid Shell Structures

Shape optimization of Shell and Spatial structure
(PDF)
Lattice Shell for Space Vehicles
(PDF)
International Association for Shell and Spatial Structures
Solid mechanics Structural system {{Civil-engineering-stub

Definition

Types

See also

References

Further reading

External links