Numerical investigation into plastic hinge formation in arched corrugated thin-walled profiles

The paper concerns thin-walled corrugated steel profiles used as arched roofing in architectural structures. Corrugation formed on the profile surface when the profiles are shaped affects their rigidity and load capacity. The complicated geometry of a profile surface prevents the creation of an analytical description based on the thin film theory. A loss of stability in this kind of profile is related to the formation of local instabilities in the early stage of local plastic mechanisms development. To that end, it is more relevant to identify the lower limit of load capacity to estimate the overall load capacity of the profile. The results obtained by the numerical calculations demand a thorough analysis of the map of strain, which is difficult because there are no clear quantitative criteria describing the beginning of plasticisation formation. The paper presents a method of analysing the results of numerical calculations based on the identification of a perturbation component of displacement in selected points of the profile. The method is based on a discrete Fourier transform and allows the establishment of an estimation criterion for the lower limit of a profile's load capacity.