Nonlinear performance of continuum mechanics based beam elements focusing on large twisting behaviors

In this paper, we present the nonlinear formulation and performance of continuum mechanics based beam elements, in which fully coupled 3D behaviors of stretching, bending, shearing, twisting, and warping are automatically considered. The beam elements are directly degenerated from assemblages of 3D solid elements under the assumptions of Timoshenko beam theory. Therefore, cross-sectional discretization is possible and the elements can model complicated 3D beam geometries including curved and twisted geometries, varying cross-sections, eccentricities, and arbitrary cross-sectional shapes. In particular, the proposed nonlinear formulation can accurately predict large twisting behaviors coupled with stretching, bending, shearing, and warping. Through various numerical examples, we demonstrate the geometric (and material) nonlinear performance of the continuum mechanics based beam elements.