Direct-formed and continuous-formed rectangular hollow sections — Comparison of static properties

• Cold-formed RHS properties by direct- versus continuous-forming are evaluated.
• “Column curve” for direct-formed RHS in compression determined
• Residual stress measurements and tensile properties compared for the two RHS types

This paper compares the static properties of a total of seven cold-formed rectangular hollow sections (RHS) manufactured by different methods: (1) direct-forming, (2) continuous-forming, and (3) continuous-forming plus stress-relieving by heat treatment. The static properties compared are: (1) tensile stress–strain behaviour and ductility around the cross-section, (2) compressive stress–strain behaviour of the entire cross-section, and (3) longitudinal residual stress around the cross-section. The maximum values of longitudinal compressive residual stresses estimated from the stub column test results are used to check the accuracy of the longitudinal residual stress measurements from strips. Finally, the measured longitudinal residual stress gradients are incorporated into column models to study the column behaviour of RHS with different production histories. It is found that, in general, the static properties of a direct-formed RHS are midway between those of its continuous-formed and continuous-formed-stress-relieved counterparts.