The shell mainly resists the external load with the mid-plane stress uniformly distributed along the thickness, rather than with the bending stress varying along the thickness. This internal force feature of the shell makes it more fully utilize the material strength than the flat plate, thus having a greater load-bearing capacity. In hydraulic engineering, shells are widely used, such as hyperbolic flat shell gates, arch dams, etc. Shell theory belongs to the category of applied elastic mechanics, and it is necessary to introduce new assumptions in addition to the basic assumptions of elastic mechanics. It includes thin shell theory and medium-thick shell theory.