Parametric finite element analysis of steel beams subjected to lateral torsional buckling

Lateral torsional buckling is a failure criteria for beams in flexure. The AISC defines lateral torsional buckling as the buckling mode of a flexural member involving deflection normal to the plane of bending occurring simultaneously with twist about the shear center of the cross-section. This failure criteria occurs when the compression portion of a beam is no longer sufficient in strength and instead the beam is restrained by the tension portion of the beam, which causes deflection or twisting to occur. The purpose of this study is to determine whether the allowable lateral torsional buckling stresses defined in AISC are conservative with eigenfunction finite element analyses. In this scope, four compact I-Sections were modeled, each of them with double symmetrical dimensions separately for parametric analyses. Besides, loading condition performed via constant bending moment and trianbular bending moment distribution. Beam models on which linear analyses were performed by using finite element analysis software, ANSYS R14.5/Structural to observe the lateral torsional buckling of steel beams were constructed as simply supported and cantilever beams. Therefore, a 4-Dimensional global structural string with 1(I-section) x 4(double symmetric parametric models) x 2(loading conditions) x 1(software) x 2(analyses) x 4 (span lengths)= 64 entries was progressed to cover all thesis researches. To simulate the actual beam behavior, solver operators in ANSYS is manually optimized instead of performing default configurations. Error spectrum lies between the limits of 1.92% and 43.74% for the simply supported beam models, beam models these limits are bounded with very close values as 0.22% and 1.37%. Finally, it has been obserbed that, ANSYS software converges to AISC standarts with an absolute average error value of 11.16%.