Improved buckling reduction factors for existing steel columns accounting for different imperfections

The presented research aims to develop global and local buckling reduction factors that account for the impact of amplified geometrical imperfections and the variability of residual stresses on the buckling resistance. The improved buckling coefficients might be necessary for analysing existing structures, which often have larger imperfections than the manufacturing tolerances. Advanced GMNI analyses are employed to investigate pure local and global buckling resistances of I- and box-section columns, incorporating accurate non-amplified local and global imperfections. A parametric study is conducted to systematically investigate the impact of enlarging the imperfection factors and varying residual stresses. The local and global buckling formulas specified in EN1993-1-5 and EN1993-1-1 are calibrated against laboratory test results and/or GMNI analyses to account for the influence of imperfections and residual stresses. Similar calibration process is performed within the current study by modifying the imperfection factor α in the buckling formulas taking into account the enlarged imperfection magnitude. The result of the current study enables designers to refine the estimation of the buckling capacity when actual imperfections and residual stresses deviate from those employed during the design phase. • Global and local buckling resistances are investigated using GMNIA. • The effects of enlarged imperfections and varying residual stresses are evaluated. • Local and global buckling formulas are calibrated against GMNIA. • Buckling formulas are developed considering amplified imperfections and residual stresses. • The applicability of the proposed formulas for interaction buckling is evaluated.