Lateral–torsional buckling assessment of steel beams through a stiffness reduction method

• Stiffness reduction method developed for the LTB assessment of beams
• Shell finite element models validated against existing experimental results
• Comprehensive verification of the stiffness reduction method against FE results
• Illustration of the application of the method to irregular and multi-span beams

This paper presents a stiffness reduction approach utilising Linear Buckling Analysis (LBA) with developed stiffness reduction functions for the lateral–torsional buckling (LTB) assessment of steel beams. A stiffness reduction expression is developed for the LTB assessment of beams subjected to uniform bending and modified for the consideration of moment gradient effects on the development of plasticity. The proposed stiffness reduction method considers the influence of imperfections and plasticity on the response through the reduction of the Young's modulus E and shear modulus G and obviates the need of using LTB buckling curves in design. The accuracy and practicality of the method are illustrated for regular, irregular, single and multi-span beams. In all of the considered cases, the proposed method is verified against the results obtained through nonlinear finite element modelling.