Linear and Nonlinear Thin Shell Analysis Using A Mixed Finite Element with Drilling Degrees of Freedom.

A study on the linear and nonlinear behaviour of thin plates and shells is described in this paper. In order to deal with engineering practical structures as box girder structures and stiffened plates and shells, a family of degenerate shell elements is developed incorporating the drilling degree of freedom (ddof) using a penalty approach with a constraint equation between the ddof and the classical rotation about the normal to the misdurface of the shell. The assumed natural strains technique is used to alleviate the different locking phenomena being able to affect the behaviour of these elements. The geometrically and materially nonlinear analysis is then performed for isotropic and anisotropic materials, and several examples are treated and their results compared with exiting published solutions. The DDSE performs well and is free of any looking. The obtained results confirm its generality, versatility and efficiency.