Determination of elastic and dissipative properties of concrete under dynamic deformation

Vibration diagnostics is one of the most promising approaches for the diagnostic of reinforced concrete structures integrity, which analyzes natural vibrations caused by impact loads. It concentrates on the propagation of the shock wave through the elements of the structure and the effect of defects on this process. An important element of the shock wave control system is a mathematical model of the structure. The mathematical modeling accuracy is ensured by a precise determination of the material elastic and dissipative characteristics. This aspect is essentially important for concrete since its characteristics may vary much. The paper presents a theoretical and experimental approach to determining elastic and dissipative characteristics of concrete. In the framework of the viscoelastic model, the deformation response of a concrete specimen to a localized shock impulse load is analyzed. A numerical solution of the initial boundary value problem is obtained by the finite-element method using the ANSYS software. Based on this solution, the structural scheme of experiments has been obtained. In the experiments, free vibrations of the specimen are excited using a striker equipped with a vibrometer. The deformation response at reference points of the sample is recorded with a laser vibrometer. A special iterative procedure ensuring the agreement between the numerical and experimental results is developed. The agreement is achieved by the correction of the mechanical characteristics of the material. The reliability and effectiveness of the proposed approach are demonstrated by considering the vibration processes in a concrete specimen. Model parameters are obtained for description of elastic and dissipative characteristics of concrete at frequency range of 5.6±0.5 kHz. The proposed algorithm can be used to identify the properties of concrete in any frequency range. It represents the possibilities for determining the frequency dependence of the elastic and dissipative properties of materials. The described approach can be used to identify the elastic and dissipative characteristics of other materials.