Enhanced buckling reduction factors using amplified imperfections for existing steel structures

Abstract

The topic of the paper is the buckling analysis of existing structures having enlarged imperfections, which might reduce the buckling capacity during the reuse of steel structures. The research aims to develop global and local buckling reduction factors that take into account the presence of enlarged imperfections, which often are observed in existing steel structures. GMNI analyses are conducted on I- and box-section columns subjected to pure compression, incorporating accurate local and global imperfections treated as non-amplified imperfections. Multiple amplification ratios are used to enlarge the value of these imperfections within the numerical parametric study. The local and global buckling formulas specified in EN1993-1-5 and EN1993-1-1 were previously calibrated against GMNI analysis that considers the effect of residual stresses and geometrical imperfections. A calibration process is performed within the current study by modifying the value of the factor α in the global and local buckling formulas to obtain the buckling resistances determined by enlarged imperfections. The developed formulas are subsequently evaluated against the interaction buckling resistance of local and global buckling behaviour. Statistical measures are also employed to assess the resistances derived from the developed formulas against GMNI results for pure local, global, and interaction buckling resistances. This paper provides a tool for designers to estimate the buckling capacity when existing imperfections surpass those assumed during the design phase.