The effect of prebuckling deflections on the lateral‐torsional buckling of beams: numerical studies

In this research the effect of prebuckling in‐plane deflections on the critical moment to lateral‐torsional buckling of beams is investigated. Though this topic is already discussed in the literature, the relevant papers show that there are some discrepancies in the proposals and results from the various authors. In this paper a numerical parametric study is reported, conducted on doubly symmetric simple supported I‐shaped beams. The critical moment values were calculated with and without considering the effect of prebuckling deflections. Various methods were considered, including analytical formulae, thin‐walled beam finite element, and shell finite element calculations. The results justify that the in‐plane deflection has a positive effect on the critical moments, and that the effect is essentially determined by the ratio of in‐plane and lateral rigidities. However, the results highlight that the moment‐increasing effect of the prebuckling deformations can be much smaller compared to the prediction of the analytical formulae, if a shell finite element model is employed.