Focusing on Problem of Lateral Torsional Buckling of Beams with Web Holes

This paper deals with the problems of analysis and the design of perforated thin-walled steel Sigma beams with respect to lateral torsional buckling (further LTB). The application of Sigma profiles is in the storage systems and expedient flooring structures as floor girders. In some cases, the beams are not laterally restraint and therefore the effect of lateral torsional buckling may occur. First the theoretical calculations according to the design procedure listed in European standard EN 1993-1-1 and Czech national annex NB.3 are being performed. These calculations are valid for the beams with the uniform cross-section only without any rules for the beams weakened by holes. Therefore the substitute cross-section is being established and the cross-section characteristics are defined as the weighted average of the characteristics for the full section and for the section weakened by holes. The calculated elastic critical moments for the substitute cross-section properties are verified by the FEM calculations on the beam with variable cross-section. This theoretical approach is verified by testing in laboratory conditions. The experiments are being carried out on the specimens of three different beam lengths. The test results are statistically evaluated according to EN 1090 and the characteristics bending resistances obtained from tests are compared with the values calculated according to EN 1993-1-1 and Czech national annex NB.3 using the cross-section characteristics of substitute cross-section.