Imperfection Tolerances During the Erection of Steel Plate Girders and Geometrical Nonlinearities

This work aims to prove that the strict initial imperfection tolerance limits proposed by the American AWS D1.1/D1.1M and the European EN 1090-2 codes could be relaxed for the webs of the most encountered steel I-plate girders subjected to local bend-buckling during their erection phase. To achieve this scope, a parametric study was done involving 36 perfect and 612 imperfect web models with varying aspect ratio, slenderness ratio, initial imperfection amplitude, and stress ratio using Abaqus/CAE by Finite Element (FE) linear buckling analyses then FE geometrically and materially nonlinear analyses with imperfections included (GMNIA). After investigating the results, two main research novelties were found. An easily applicable equation to determine the ultimate strength of webs subjected to direct stresses, which is a function of not only the slenderness ratio and stress ratio (as in other research) but also a function of the initial imperfection amplitude, was derived. Secondly, a tolerance limit equation that is a function of not only the slenderness ratio but also the stress ratio, thus considering the symmetry of the section of plate girders, has been derived. The derived tolerance limit equation provides acceptable and inclusive parameter-wise imperfection tolerances for webs of plate girders so as to relax strict and costly tolerance limits. The results obtained show that for monosymmetric I-plate girders during erection, EN 1090-2 and AWS D1.1/D1.1M tolerance limits can be relaxed to around 40% and 80% in less slender webs and close to 60% and 200% in more slender webs, respectively