Imperfection sensitivity analysis of lipped channel columns at high temperatures

Abstract An imperfection sensitivity analysis is carried out on cold formed lipped channel columns integrated in wall structures. The equations given in Eurocode 3: Part 1.3 and finite element analyses are used to evaluate the flexural buckling strength and ultimate strength of the sections. The analyses are performed at both room and fire temperatures by introducing corresponding material data values obtained from high temperature transient tensile tests into the models. The purpose of the study is to evaluate the possibility of using normal temperature design formulae directly at high temperatures and to evaluate the influence of the choice of initial geometric imperfections on the modelled behaviour of the columns. The analytical estimations are compared to the results of the finite element analyses, which in turn are validated using available test results. It is shown that the magnitude of the modelled types of local imperfections has an effect on the compression stiffness of the members, whereas the magnitude of global flexural imperfections has more influence on the ultimate strength obtained in the analyses. The influence of the choice of buckling curve at high temperatures is discussed.