PROBABILISTIC ASPECTS IN THE INTERACTIVE GLOBAL AND LOCAL BUCKLING OF THIN-WALLED COLUMNS

摘要

As a result of the presence of unavoidable initial imperfections, all stability phenomena in compressed thin-walled bars (i.e. the buckling of the bar as a whole and that of its plates progress in a permanent interaction. Geometrical imperfections (i.e. the imperfections of the cross-sectional shape and the out-of-straightness of the column) are to a high degree uncertain. In the authors' study of the impact of such imperfections on the load-carrying capacity of compressed thin-walled bars, the relevant geometrical quantities are treated as random variables. In so doing, the "shape" of the imperfections is assumed to be affine to the first eigenvalue modes of the corresponding global and local buckling problems. In the paper, the problem is studied, on columns with typical slenderness ratios and having a closed (box) cross-section, using the programme system ANSYS, able to take account of both large deflections and plastic deformations. The randomness of the problem is dealt with by adopting the simulation technique Latin Hypercube Sampling. The statistical parameters of the ultimate loads of the columns are assessed with due account to the statistical character of the influence of initial imperfections. This is expressed by means of sensitivity analysis.