Shell st1·uctures mobilize geomet1·y to activate both the membrane and the flexural intemal force systems to efficiently suppo1·t any distl'ibuted loads applied to those st1·uctures. Based p1·ima1·ily on theit· efficiency, these geometric structural fo1·ms are employed in a number of industrial applications such as p1·essure vessels, containment stl'uctu1·es, etc. where the pl'incipal function of the stl'ucture is to contain or sustain a pa1·ticulm· loading environment.This selection is especially true when substantial loads m·e involved such as high internal pressures. The shell structmes selected fo1· these applications tend to be simple fo1·ms, most frequently combinations of various shells of 1·evolution such as cylinders, cones, sphe1·es and (fo1· the p1·essure vessels) the tomsphel'ical o1· ellipsoidal shapes because of theit· ability to 1·espond to most loads by a membrane state over the majo1· a1·ea of the shell. Edge effects a1·e confined to a nat'I'OW zone neat' the edge Ol' around a zone of discontinuity that may be present as a result geometl'y changes.