Investigations of initial imperfections of steel scaffold structures

Analysis and design of structures sensitive to second order effects require to take into account initial imperfections. Scaffold structures, due to their low rigidity, are very sensitive to second order effects. The accuracy of the design of such structures is based in part on the estimation of initial imperfections affecting the structure. In the 60s, the C.E.C.M., the European Convention of Steel Construction, has launched a test campaign to determine the degree of initial imperfections of each type of cross‐section. Five buckling curves have been established. The European design code for steel structures, Eurocode 3 Part 1‐1, classifies cold‐formed hollow tubular sections among sections with many imperfections, i.e. curve ‘c'. A test campaign has launched to analyse the experimental buckling curve behaviour of cold‐formed hollow sections of scaffold structures. Nineteen buckling tests on simply supported members and nine buckling tests on scaffolding ladders, from various European suppliers, have been carried out. Statistical studies of the experimental results highlight that the estimation of the initial imperfection currently defined for the cold‐formed tubular sections is far too penalizing for the sections used in the field of scaffolds.