Out-of-Plane Advanced Analysis of Steel Structures (No. R823)

Attempts to extend practical advanced analyses of the in-plane behaviour of 2-D steel frames under in-plane loading to out-of-plane behaviour have been largely unsuccessful because of difficulties in modeling the effects of yielded zones, load heights, interactions between twist and axial force and moments, and end warping restraints. Practical advanced analyses of out-of-plane behaviour need to be able to account for the influences of moment and axial force distributions, load heights, and end restraints on elastic and inelastic lateral buckling, and to be consistent with the code formulations of beam and column out-of-plane strengths. It is proposed in this paper that the advanced analysis of 2-D frames for which local buckling is prevented be simplified by first carrying out an in-plane analysis using one of the presently available plastic hinge methods, and then by using a practical advanced analysis of the out-of-plane behaviour which is based on an inelastic lateral buckling analysis which includes allowances for residual stresses and initial crookednesses and twists. The paper makes a number of suggestions of how to develop such a practical method of advanced out-of-plane analysis for 2-D frames for which local buckling is prevented