Research on the evolution characteristics of creep energy in rubber concrete and the damage constitutive model

To investigate the evolution law of energy and the damage constitutive model of concrete with different rubber replacement ratios under uniaxial creep, this paper systematically studied the creep energy evolution law of rubber concrete using uniaxial creep-unloading tests. The study focused on the transformation and dissipation mechanisms of energy in rubber concrete during creep, alongside the establishment of damage creep constitutive models for concrete with varying rubber replacement ratios. The findings reveal that: (1) The elastic strain energy density (u^e) of concrete with varying rubber replacement ratios demonstrates a linear decline over extended creep time, characterized by linear attenuation. (2) Based on the results of uniaxial creep-unloading tests, this study proposes a method for calculating creep energy in concrete based on the linear attenuation characteristics of u^e. (3) The dissipated strain energy density (u^d) and input strain energy density (u) of concrete with different rubber replacement ratios increase over time, and this growth can be divided into the decay growth stage, uniform growth stage, and accelerated growth stage. (4) During the creep process, as the creep time increases, the proportion of u^d to u in concrete with different rubber replacement ratios gradually increases, reaching its maximum at the critical point of accelerated creep and post-peak, and the higher the rubber replacement ratio of the concrete, the smaller the proportion of u^d to u at the critical point of accelerated creep and post-peak. (5) This research develops a viscoelastic-plastic-damage coupled constitutive model founded on energy dissipation, adept at delineating the deformation curves of concrete of varying rubber replacement ratios during creep. The research results not only have positive significance for improving the recycling of waste tires, but also provide new ideas for the establishment of the creep constitutive model of concrete.