Nonuniform shear warping effect in the analysis of composite beams by BEM

• Formulation for the nonuniform shear warping analysis of composite beams.
• Composite beams under general torsionless loading and boundary conditions.
• The proposed method employs a BEM approach and high accuracy is achieved.
• Shear lag phenomenon is investigated.
• Comparison with FEM solid models demonstrates the accuracy of the method.

In this paper a general formulation for the nonuniform shear warping analysis of composite beams of arbitrary simply or multiply connected cross section with at least one axis of symmetry, under general boundary conditions is presented. The beam is subjected to the combined action of arbitrarily distributed or concentrated transverse loading passing through the shear center of the cross section, as well as to bending and warping moments. The nonuniform shear warping distribution is taken into account by employing one independent warping parameter multiplying a shear warping function, which is obtained by solving a corresponding boundary value problem, formulated exploiting the longitudinal local equilibrium equation. By taking into account the aforementioned nonuniform shear warping distribution, the developed formulation is capable of capturing “shear lag” effect on beams under flexure. Three boundary value problems are formulated with respect to the displacement and rotation components as well as to the independent warping parameter and solved using the Analog Equation Method, a Boundary Element Method based technique. The warping function and the geometric constants including the additional ones due to warping are evaluated employing a pure BEM approach.