Rectangular timber columns subjected to eccentric axial loading are proneto lateral-torsional buckling, an instability phenomenon in structural timberdesign. Accurate prediction of lateral-torsional buckling is essential forensuring structural safety, especially given the increased use of timber inlarger structures with slender profiles. This thesis evaluated the accuracy andreliability of the Eurocode 5 interaction formula (6.35) for lateral-torsionalbuckling of rectangular timber sections, through numerical analyses usingAbaqus. A comprehensive parametric study was conducted using finiteelement simulations automated by Python, investigating how parameterssuch as column length, cross-sectional aspect ratio h/b, and load eccentricityinfluence the buckling load and structural stability.

The results showed that the existing Eurocode interaction formuladoes not consistently provide conservative predictions. For columns withhigh relative slenderness ratios, large cross-sectional aspect ratios, and lowto moderate eccentricities, the Eurocode interaction formula tends to yieldunsafe results, while it tends to provide conservative estimates for casesinvolving large bending moments combined with smaller axial forces. Toaddress these shortcomings, an optimized interaction formula was developed,featuring an adaptive exponent α that depends on the parameter kc, andthe h/b ratio. The optimized formula ensured safer predictions compared tothe current Eurocode interaction formula.