Short- and long-term measurements of resonance frequencies on prestressed concrete beams

In English Currently, no method exists for determining the prestress forces in prestressed concrete structures. According to the theory of acoustoelasticity, the modulus of elasticity of concrete is stress dependent, which means that the resonance frequency of a concrete structure also is stress dependent. In this study, both short-term and long-term measurements of the resonance frequencies of four prestressed concrete beams were performed. The results show that the acoustoelastic effect in concrete is measureable and that the resonance frequencies increase with the applied compressive stress and that the prestress losses can be monitored through measurements of the resonance frequencies.