Correlation between Coda Wave and Stresses in Uni-Axial Compression Concrete

Abstract

Stresses in structures are usually converted by measured strains based on corresponding constitutive relations of materials. However, it is difficult to determine the constitutive relation of the material accurately, which leads to significant uncertainty of the converted stresses. This paper proposed a method to estimate the stresses in concrete by using the coda wave interference technique and established a model to describe the relation between the deformation of microcracks and the sound velocity. Based on the experiments, the development law of the coda waves with different frequencies of sound signal propagating in concrete was verified and discussed, and the change of the coda wave velocity during the loading and unloading of the specimen was tested. Parameters involved in the established model were regressed according to the experimental data. The analysis results show that the method can be used to test concrete stress and has a desirable accuracy. coda wave analysis method in 1969 [12]. In 2002, Snieder et al. used CWI to estimate the nonlinearity of the seismic wave velocity and found that CWI exhibited extreme sensitivity to variations in the medium [13]. After that, the researchers further improved the effectiveness of CWI on the measurement for velocity variation in concrete caused by temperature [14], micro damage [15][16][17], and a uniform stress field [18]. In 2014, Niederleithinger conducted an experimental study to demonstrate the effectiveness of CWI in concrete stress measurement [19].McCann and Forde pointed out that the development of NDT should depend on a better understanding of the performance of materials and forward modeling. Moreover, it should put forward a practical method to obtain high accuracy and realistic feasibility results from NDT [4]. Therefore, the correlation between the stress and the coda wave velocity of concrete should be discussed for the better application of CWI technology in concrete stress detection. Microcracks in concrete close or expand under stresses, leading to changes in the medium's characteristics. The tiny changes in the concrete acoustic-elasticity properties can be amplified by CWI, and its accuracy can reach up to 2 × 10 −5 [6]. It is feasible to estimate stress using CWI according to the correlation between the coda wave velocity and microcracks [20]. This paper discussed the mechanism of detecting the stress of concrete using the CWI technique. A correlation model of sound velocity and stress in concrete based on the acoustic elasticity theory was proposed. An experimental study was conducted to measure the changes of wave velocity in the concrete under stress according to the CWI technique. Overall, this paper provided a new approach for stress estimation in concrete structures. Correlation Model of Sound Velocity and Stress in ConcreteSound velocity in concrete is mainly determined by the elastic parameters of concrete. The development of microcracks in concrete under stresses would change the elastic parameters of the concrete medium, resulting ...