Rate-dependent damping properties of recycled aggregate concrete from creep perspective

Abstract

Creep and damping, which are two important static and dynamic properties of concrete material, have similar mechanical characteristics and have not been studied integratedly. This paper aims to develop a new method to investigate the creep and damping properties of recycled aggregate concrete (RAC) from viscoelastic perspective. In this research, a fractional order derivative viscoelastic creep model of RAC under different load levels was proposed. Then, with the consideration of recovery coefficient and time-dependent behavior, the damping properties of RAC based on interconversion between viscoelastic functions were investigated. The creep tests of reinforced RAC beams, accompanied by loading and unloading tests, were conducted to study the viscoelastic properties, meanwhile, free-vibration tests at different ages were carried out to analyze the time-dependent damping behavior of RAC. Test results indicate that compared with three parameter model and generalized three parameter model, fractional three parameter model is a feasible viscoelastic model to characterize both creep and damping behavior of RAC. The creep compliance of RAC is higher than that of NAC, and increases with the increasing of load level. The damping property of RAC decreases with the increasing of load frequency and the decreasing of load level, meanwhile, the damping property of RAC is related to recoverable instantaneous deformation. In addition, the damping property of RAC decreases with the increasing age when it is not considering load, but increases when it is subjected to sustained load. The proposed damping model was validated with a database of RAC damping in published literatures.