Buckling analysis of I-section portal frames with stochastic imperfections

This work examines the effect of random geometric imperfections in the buckling response of I-profile steel beam–column members as well as portal frame structures. Geometric imperfections are assumed to be non-homogeneous Gaussian random fields. Samples of these fields are generated using the spectral representation method with evolutionary power spectra derived from experimental measurements using the method of separation. A number of samples of random imperfect geometries are generated and simulated with detailed discretization with triangular shell finite elements. The stochastic buckling loads are determined in the context of brute force Monte Carlo simulation by repeated material and geometrically nonlinear finite element analyses. Single beam–column members are subjected to pure axial compression while the portal frames are tested for lateral loading. Various types of boundary conditions are implemented and histograms of bucking loads are derived for each case examined leading to useful conclusions for this type of structures, regarding imperfection triggered buckling response and buckling load variability.