Shape-orthotropic stressing–bending plate model

In structural engineering practice, composed plate structures are normally calculated as orthotropic plates in bending, applying either thin plate theory (Kirchhoff) or thick plate theory (Mindlin/Reissner), without accounting for the eccentricity of neutral planes in different directions. In reality this eccentricity causes a different force distribution, in which not just bending moments, twisting moments and transverse shear forces occur, but membrane forces as well. As a consequence, a coupled type of stretching–bending-shear orthotropy occurs. The present article presents a method to determine the required smoothed cross-section rigidities as an input in FEM software, which offers functionality for analysis of this type of orthotropy. To compute rigidity properties it is sufficient to have on hand a FEM program for 2D analyses. It is, however, likely that some enhancements have to be added to existing FEM software. Examples are included to show the reliability of the method and consequences in plate results.