Strain rate behaviour in tension of S355 steel: Base for progressive collapse analysis

• Experimental study in a wide range of strain-rates of mild steel.
• Mechanical tensile properties and strain energy evaluation.
• Suitability of two commonly used constitutive relationships.

This paper presents the strain rate behaviour in tension of the S355 structural steel using a modified Split Hopkinson Tensile Bar for the mechanical characterisation at high strain rates (300 s-1s-1, 500 s-1s-1 and 850 s-1s-1), and a Hydro Pneumatic Machine for intermediate strain rates (5 s-1s-1 and 25 s-1s-1). These data are collected with the intention of setting down the basis for the enhancement of a progressive collapse analysis, that is, by the way, a dynamic event. Results show that the structural steel S355 is strain rate sensitive, keeping its strain hardening capacity with increasing strain-rates. Also the strain energy and the ductility show a marked influence to increasing strain rates. Two of the most used constitutive laws (Johnson–Cook and Cowper–Symonds) are considered and the accuracy of these models is demonstrated. The results can be of great interest for the assessment of robustness in structures where progressive collapse may be triggered by the failure of parallel steel members like, e.g., in the case of cable-stayed or suspension bridges and of large-span 3D trusses subjected to high strain-rate events.