Numerical and experimental investigation of lateral torsional buckling of wood beams

The present study reports the results of a full-scale experimental and numerical investigation aimed at predicting the elastic lateral torsional buckling capacity of wooden beams. The experimental component consists of 18 Spruce-Pine-Fir (SPF) No. 1/No. 2 grade lumber joists consisting of five 38 mm × 184 mm × 4200 mm, six 38 mm × 235 mm × 3600 mm, and seven 38 mm × 286 mm × 4200 mm specimens. For each specimen, the shear and longitudinal elastic moduli are first determined experimentally through non-destructive tests. A full-scale bending test is then conducted on each specimen, to determine its elastic lateral torsional buckling resistance. A 3D finite element model is developed to predict the lateral torsional buckling resistance for each specimen based on the experimentally determined shear and longitudinal elastic moduli. The validity of the finite element analysis is assessed through comparisons with full-scale test results. The validated model was used to assess the Eurocode provisions and it was found that for simply supported end conditions the code equation seemed reasonable and slightly conservative. However, for cantilevered beams, the Eurocode provisions seem to be overly conservative for the case of bottom edge loading and non-conservative for the case of top edge loading. Changes have been proposed to the wording of the effective length adjustment and the results based on the revised definition provides critical moment predictions that are conservative and more consistent for cantilevers under top and bottom edge loading.