High strain rate behaviour of cold-formed rectangular hollow sections

• High strain rate properties for cold-formed hollow sections studied.
• Split Hopkinson pressure bar tests performed on RHS of various types and sizes.
• Yield stress dynamic increase factors identified for strain rates up to 1000 s−1.
• Dynamic properties studied in compression and tension.

For blast- or impact-resistant design of steel structures, it is important to use realistic properties of steel under high strain rate. In particular, the substantial rise in yield stress under high strain rate may have important effects on the dynamic behaviour of a steel structure. The high strain rate properties of some steels have been studied in the past; mostly reinforcing bars, plates and hot-rolled sections. The goal of this research is to remedy the lack of knowledge on the high strain rate behaviour of cold-formed steel hollow sections. In this study, four cold-formed Rectangular Hollow Sections (RHS) manufactured by two different cold-forming methods (direct-forming and continuous-forming) have been examined. The dynamic properties of the RHS specimens were determined by performing a total of 166 compressive and tensile Split-Hopkinson Pressure Bar (SHPB) tests at strain rates ranging from 100 to 1000 s−1 and their dynamic yield stresses were compared to their static yield stresses, to characterise the strength enhancement of cold-formed RHS under such loading rates.