Acoustoelastic effects on the resonance frequencies of prestressed concrete beams—Short-term measurements

In this study resonant acoustic spectroscopy was applied during static loading and unloading of three prestressed concrete beams in the context of acoustoelasticity. At each load step multiple modes of vibration were measured using an accelerometer and a small impact source. It was found that the measured resonance frequencies increased with increasing compressive stress in a manner which can be predicted using a non-linear finite element model based on Murnaghan's third order elastic theory. Previous results from experimental studies on concrete bridges indicate that measured structural resonance frequencies increase with increasing prestress forces. These results have been difficult to explain theoretically and the results from this study can possibly provide a new theoretical basis for the observed stress dependency of the resonance frequencies of concrete structures. Furthermore, the results indicate that a change in the state of stress in a concrete structure can be detected or monitored by measuring one or several resonance frequencies.