Abstract：Ultrasonic velocities in the concrete highly rely on its stress state. The nonlinear variation process of the velocities with the increase of the stress cannot be explained by current theories. Aiming at the prediction of ultrasonic velocities in the stressed concrete, this study extended the elastoplastic-damage concept from the infinitesimal strain field to the finite strain field, and proposed the new formulations for the calculation of the velocities with the initial elastic strain starting from the unloaded configuration. Based on the classic constitutive equations for concrete under uniaxial compression, the plastic strain and damage state was derived as the initial conditions for the velocity computation. This methodology has been verified by simulating experimental results. Theoretical results proved that this model could well describe the nonlinear variation process of the velocities as the stress raises. Sensitive analyses imply that the plastic anisotropy of the unloaded configuration and the damage effect of the 3rd order modulus can be ignored. Also, most of the test results from past research have underestimated the actual third order moduli of concrete.
2025, Vol. 46 
