Locking-free isogeometric collocation formulation for three-dimensional geometrically exact shear-deformable beams with arbitrary initial curvature

This paper presents a displacement-based and a mixed isogeometric collocation formulations for three-dimensional geometrically exact shear-deformable beams with arbitrarily curved initial geometry. Strong forms of both formulations are consistently linearized with respect to the underlying configuration manifold. High efficiency is achieved by using a geometrically consistent kinematic model in which incremental rotations are parametrized through the spatial rotation vector. Several numerical tests demonstrate that the proposed mixed formulation is totally locking-free for any choice of approximation degree. Mixed formulation also exhibits higher robustness in the incremental-iterative algorithm. Elimination of shear locking and low computational cost assured by the combination of isogeometric collocation with a consistent kinematic model result in a very efficient, accurate and geometrically powerful method able to handle geometrically complex beam problems.