Plastic resistance of Z-sections under various internal forces

Analysis of plastic resistance of Z-sections under combination of various internal forces is presented. Hot-rolled Z-sections of Class 1, 2 or 3 are analysed. Elastic cross-sectional properties of hot-rolled Z-sections may be taken also from German standard DIN 1027:2004-04. It is shown that some values in DIN 1027:2004-04 are incorrect. Roll formed Z-sections may be seen in various steel constructions such as commercial buildings, large storage bins, mezzanine flooring, racking, residential garage doors, fencing, etc. Some commercial computer programs calculate elastic and plastic cross-sectional characteristics and resistances to the both kind of axes: y-y and z-z and also to principal axes u-u and v-v. Unfortunately some of their results are incorrect. The paper offers for Z-sections the formulae for calculation of: a) cross-sectional elastic and plastic characteristics, b) elastic and plastic resistances including their maximum values which may be achieved with combination of other internal force. Numerical examples show details of calculation, comparison with results of other sources and interaction diagrams as well. The presented procedure will be useful for designers in practice, authors of computer programs and participants in educational processes.