Mechanical behaviour of B500A rebars: Effect of elevated temperature and high strain-rate

Abstract

Within their lifetime, reinforced concrete structures can be subjected to extreme loadings such as fire and blast, which are often combined or occur in sequence. Frequently, a fire within a structure causes internal blasts, leading to catastrophic damages and sometimes may be the main cause of the triggering of progressive collapses. Thus, it appears crucial to investigate the mechanical response of concrete and rebars both under high strain-rate and elevated temperature. This experimental work deals with the tensile behaviour of B500A cold worked reinforcing steel usually adopted for stirrups and welded wire meshes. Three conditions corresponding to different elevated temperatures (200^∘C, 400^∘C and 600^∘C) and high strain-rates (250, 500, 900 s⁻¹) have been imposed to each sample by means of a Split Hopkinson Tensile Bar equipped with a water-cooled induction heating device. The obtained results have been compared with those related to other reinforcing steels, having same grade, and tested in similar conditions, e.g. B500B and stainless steel rebars. Moreover, tests at room temperature (20^∘C) and high strain-rates have been performed and the obtained results have been used to evaluate the dynamic reduction factors associated to the main mechanical properties. Finally, the material parameters for the commonly used constitutive relationships have been calibrated as well. The results of the experimental campaign undertaken are fundamental for the design and the assessment of reinforced concrete structures subjected to the aforementioned combined extreme conditions.