A shell is subjected to forces that act in its own plane. Examples of such structural elements in ships and offshore structures, are flanges and webs in beams. Beams are here interpreted in a wide sense. Accordingly, the bottom and deck in a ship can be regarded as flanges of the hull girder, while the side of the ship will act as the web of the beam.
Focusing on beams with flanges and webs, they were efficiently analysed by elementary beam theory. However, when the web of a beam is high as compared to the beam length, elementary beam theory will give an inaccurate result. For such cases, the theory of shells will hence be a useful tool.
The following topics are covered here:
If you load a shell up to a certain point, it will "buckle" out. Here, more advanced theory has to be introduced. This is desscribed under "Buckling".