On the Problem of the Imperfections of the Structural Glass Members Made of Flat Glass

Abstract

This paper deals with initial geometrical imperfections of the structural glass members made of flat glass. The design of the load bearing glass structures is relatively common in modern architecture, but there is not an Eurocode on design of glass members. Thus, practical design is still a challenge for structural engineers. In the case of structural glass members with problems of lack of stability (columns, beams and beam-columns), it is necessary to know the shape and size of the initial geometrical imperfections to carry out a static design. European product standards of float glass panes distinguish several types of geometrical imperfections. In the frame of this paper, the measurement and evaluation of the most important of them – overall bend – is presented. The initial geometrical imperfections (in the shape of overall bend) were measured on the 33 specimens. But in the real structures we can recognize three types of imperfections: geometrical imperfections of a structural member (imperfect shape), structural imperfections (loading eccentricity, unknown boundary conditions) and physical imperfections (inhomogeneity, residual stresses). These three types of imperfections can be replaced by only one equivalent geometrical imperfection. The only way to find out the size of this imperfection is to carry out an experiment on flexural buckling and lateral torsional buckling. Equivalent geometrical initial imperfections were evaluated using Southwell's plot of flexural buckling and lateral torsional buckling results. The amplitudes of those imperfections were statistically evaluated and with knowing of the 5% quantile of those amplitudes, it is possible to obtain parameters of Eurocode buckling curves.This paper deals with initial geometrical imperfections of the structural glass members made of flat glass. The design of the load bearing glass structures is relatively common in modern architecture, but there is not an Eurocode on design of glass members. Thus, practical design is still a challenge for structural engineers. In the case of structural glass members with problems of lack of stability (columns, beams and beam-columns), it is necessary to know the shape and size of the initial geometrical imperfections to carry out a static design. European product standards of float glass panes distinguish several types of geometrical imperfections. In the frame of this paper, the measurement and evaluation of the most important of them – overall bend – is presented. The initial geometrical imperfections (in the shape of overall bend) were measured on the 33 specimens. But in the real structures we can recognize three types of imperfections: geometrical imperfections of a structural member (imperfect shape), structural imperfections (loading eccentricity, unknown boundary conditions) and physical imperfections (inhomogeneity, residual stresses). These three types of imperfections can be replaced by only one equivalent geometrical imperfection. The only way to find out the size of this imperfection is to carry out an experiment on flexural buckling and lateral torsional buckling. Equivalent geometrical initial imperfections were evaluated using Southwell's plot of flexural buckling and lateral torsional buckling results. The amplitudes of those imperfections were statistically evaluated and with knowing of the 5% quantile of those amplitudes, it is possible to obtain parameters of Eurocode buckling curves.