OUT-OF-PLANE STRENGTHS OF STEEL BEAMS

A general finite element method of analyzing the nonlinear effects of instability and yielding on the biaxial bending and torsion of steel I-section members with residual stresses and geometrical imperfections is presented. The analysis assumes tangent modulus behavior of thc clastic-plastic strain-hardening material, and makes simple approximations for the effects of shear on yielding and for the shear modulus of the yielded and strain-hardened material. The results obtained from a computer program based on the element are compared with a wide range of available solutions to confirm the high accuracy of the method in predicting the effects of geometrical imperfections, instability, biaxial bending and torsion, residual stresses, and yielding and strain hardening. The program is used to study the out-of-plane strengths of steel I-beams with residual stresses and geometrical imperfections by extending previous studies of the in-plane strengths of steel columns and beam columns. This study includes an assessment of the initial crookednesses and twists implied by recent formulations of beam strength.