Calibration of tensorial damage concrete material model with cyclic compression tests and ultrasound measurements

It is well known, that under uniaxial compression, a concrete specimen undergoes very different damage patterns in the loading direction when compared to the damage in the directions orthogonal to loading. Correct modelling of the anisotropic damage evolution in concrete can be described using tensor valued
damage and/or plasticity internal variables as opposed to scalar valued variables, as shown in Vilppo et al. (2021). However, the drawback of such models is the calibration of a large number of model parameters. This study investigates the feasibility of using multi-directional ultrasound wave speed measurements in
damaged concrete specimens to determine the anisotropic damage state. From the relation between wave speed measurements in different directions and stiffness tensor components, one can deduce the evolution of the stiffness tensor as a function of accumulated inelastic strain in loading direction.