Finite element modeling of open-section composite beams with warping restraint effects

A new finite element is developed to capture spanwise torsion-related warping restraint effects in open section composite beams. The new model allows for direct implementation of the kinematic boundary conditions for torsion. A Vlasov cross-section model is used to determine the beam stiffness coefficients. The new model is validated against closed form solutions for composite I-beams and detailed shell element solutions. Previous methods of modeling spanwise warping effects are reviewed and improvements in accuracy are presented. Beams with spanwise taper, elastic couplings, arbitrary warping boundary conditions, bending, and distributed torsional loadings are analyzed. For beams with uniform crosssection, the global increase in torsional stiffness is independent of distributed loadings. Warping restraint effects were found to be dependent on the crosssectional geometry in the vicinity of the restraint. For extremely slender beams, the new torsion model reduces to classic St. Venant torsioa.