Two types of geometric imperfection typically need to be considered in the analysis and design of structural
systems: global frame out-of-plumbness, also referred to as sway imperfections, and member out-of-straightness,
also known as bow imperfections; the effect of local cross-section imperfections is generally accounted for
through cross-section resistance checks. For modelling convenience, equivalent geometric imperfections are
often employed to allow for the combined influence of initial geometric imperfections and residual stresses. For
design by geometrically and materially nonlinear analysis with imperfections (GMNIA), amplitudes for equivalent bow imperfections for members are provided in EN 1993–1-14; however, no provisions exist for global
sway imperfections. Therefore, equivalent sway imperfections suitable for use in the design of steel structures by
GMNIA ϕ0,GMNIA are established herein. Two proposals for calculating ϕ0,GMNIA are presented: (1) ϕ0,GMNIA =
ϕ0,geom + α/100, with ϕ0,geom representing the pure geometric sway imperfection, and (2) ϕ0,GMNIA = α/50. In
both proposals, the varying degree and influence of residual stresses for different cross-section geometries and
axes of buckling is captured by the imperfection factor α, as defined in EN 1993–1-1 for carbon steel and EN
1993–1-4 for stainless steel, respectively. A flow chart that provides guidance on the appropriate selection of
frame and member imperfections to avoid duplication of the effects of residual stresses in design by GMNIA is
also presented.