Cyclic tensile behavior of SFRC: Experimental research and analytical model

Abstract

This paper presents an experimental investigation on the stress-strain behavior of steel fiber reinforced concrete (SFRC) subjected to uniaxial monotonic and cyclic tension. A total of 42 samples are fabricated and tested for various fiber volume fractions and aspect ratios. The entire cyclic tensile stress-strain curves are captured and the acoustic emission (AE) signals are synchronously recorded during the tensile testing. The damage progression and failure mechanism of SFRC are studied using AE characteristic parameters. The results show that the inclusion of steel fiber significantly improves the cyclic mechanical properties of concrete with respect to peak stress, peak strain, residual strength, toughness and post-peak ductility, which increase drastically with increasing fiber parameters. Moreover, the elastic stiffness is observed to degrade with increasing loading cycles and the degradation rate is remarkably alleviated as the fiber volume fraction or aspect ratio increases. However, it is noted that the steel fiber has no significant contributions on the plastic strain accumulation, meaning that the unloading elastic stiffness of SFRC is only determined by the envelope stress. In addition, based on AE results, a rapid damage evolution is observed at the formation of the first crack, with the occurrence of a stress drop and a release of concentrated AE signals. The total amount of AE activity and shear cracks in concrete increase with an increase in fiber parameters for both monotonic and cyclic loading protocols. The determinant of concrete failure mode changes from tensile cracks to shear cracks with increasing fiber volume fraction. Finally, a damage elastoplastic constitutive model is developed with the effect of steel fiber taken into consideration, and the prediction shows a close estimation of the monotonic and cyclic stress-strain responses.