Torsional buckling and post-buckling behavior of eccentrically stiffened functionally graded toroidal shell segments surrounded by an elastic medium

The nonlinear buckling and post-buckling problems of functionally graded stiffened toroidal shell segments surrounded by an elastic medium under torsion based on an analytical approach are investigated. The rings and stringers are attached to the shell, and material properties of the shell are assumed to be continuously graded in the thickness direction. The classical shell theory with the geometrical nonlinearity in von Kármán sense and the smeared stiffeners technique are applied to establish theoretical formulations. The three-term approximate solution of deflection is chosen more correctly, and the explicit expression to find critical load and post-buckling torsional load-deflection curves is given. The effects of geometrical parameters and the effectiveness of stiffeners on the stability of the shell are investigated.