Experimental and numerical investigation on LTB strengths of monosymmetric compact I-beams with thickness-stepped-flanges

This paper investigates the inelastic lateral torsional buckling, LTB, of doubly stepped singly symmetric compact I-beams under two concentrated loads. The results are obtained by conducting actual destructive tests on the beams using a testing machine and running simulation tests using the finite element program, ABAQUS. The main factors that are considered for the analyses are the degree of symmetry, the loading and supports, the stepped beam factors and the length. For this study, the beams have simple supports. The monosymmetric ratio of all the beams analyzed is fixed at 0.7. The unbraced lengths of the beams are 3 meters and 4 meters. The results obtained from ABAQUS are compared with the results from design specifications to determine the effects of steps and from proposed design equations to determine the equations’ applicability and safety. The results revealed that the stepped beams did have an increase in capacity in comparison with the prismatic beams and that the proposed equations are suitable to be used in predicting the strength of stepped beams under the observed loading condition.