A GEOMETRICAL NONLINEAR ECCENTRIC 3D-BEAM ELEMENT WITH ARBITRARY CROSS-SECTIONS

In this paper a finite element formulation of eccentric space curved b eams with arbitrary cross-sections is derived. Based on a Timoshenko b eam kinematic, the strain measures are derived by exploitation of the Green-Lagrangean strain tensor. Thus, the formulation is conformed wit h existing nonlinear shell theories. Finite rotations are described by orthogonal transformations of the basis systems from the initial to t he current configuration. Since for arbitrary cross-sections the centr oid and shear center do not coincide, torsion bending coupling occurs in the linear as well as in the finite deformation case. The lineariza tion of the boundary value formulation leads to a symmetric bilinear f orm for conservative loads. The resulting finite element model is char acterized by 6 degrees of freedom at the nodes and therefore is fully compatible with existing shell elements. Since the reference curve lie s arbitrarily to the line of centroids, the element can be used to mod el eccentric stiffener of shells with arbitrary cross-sections. (C) 19 98 Elsevier Science S.A. All rights reserved.