Torsional vibration technique for the acoustoelastic characterization of concrete

Abstract

There is no nondestructive evaluation method capable of determining stresses in concrete structural members in situ. Here, we propose and evaluate a torsional-vibration testing technique that offers an approach to estimate the stress state in concrete specimens by means of characterizing the material nonlinearity. We axially load three prismatic specimens comprising different concrete mixtures and measure their torsional vibration frequencies during four loading cycles. The fundamental torsional frequency shows a positive correlation with applied compressive stress for both loading and unloading stages after correcting for the effects of non-uniform torsion, geometric nonlinearity and changing boundary conditions. To quantify this behavior, we define the nonlinear parameter $$\beta_{G}$$ to characterize the material nonlinearity (acoustoelasticity). The values of $$\beta_{G}$$ of the initial loading cycle are lower than those of the subsequent loading cycles. However, the latter values of our concrete mixtures are consistent and similar to the values computed from previously published results. An estimate of the $$\beta_{G}$$ parameter of a concrete structural member provides a pathway for nondestructive assessment of in situ compressive stress in the member.