Structural response of cold-formed lipped Z purlins – part 1: experimental investigation

This paper reports 8 experimental tests on simply supported purlins with lipped Z-sections under gravity loads. The adopted test details are representative of the support conditions typically employed in practice with each specimen comprising two purlins connected to each other at regular intervals with angle struts used in lieu of anti-sag bars and profiled steel sheeting attached to the purlins’ top flanges via self-drilling screws. The observed failure modes included primarily distortional buckling and interactive distortional/local buckling. The moment resistance predictions of EN 1993-1-3 and the Direct Strength Method (DSM) were compared against the experimentally obtained moment resistances and it was concluded that the EN 1993-1-3 strength predictions are overly conservative, whilst the DSM offers more accurate strength predictions. The experimental results are utilized in the companion paper where a numerical study on the optimization of the lip size of Z sections is reported.