Experimental Study and Mechanism Analysis of the Dynamic Performance of Plain Concrete under Combined Compression and Shear

Concrete is obviously affected by the loading strain rate, and concrete exists in the state of shear multiaxial stress in practical engineering. Studying the dynamic response of concrete under multiaxial shear states facilitates comprehensive analysis of its actual failure behavior under complex loading conditions, thereby establishing an experimental foundation for precisely formulating dynamic constitutive models of concrete. Therefore, in this study, five axial compression ratios (0, 0.138, 0.207, 0.276, and 0.414 fc) and four strain rates (10−5/s, 10−4/s, 10−3/s, and 10−2/s) were considered. A servohydraulic machine for compression and shear was applied to conduct experimental research on the shear multiaxial dynamic mechanical properties of concrete. Different failure patterns and shear mechanical characteristic values of concrete under different loading conditions were obtained from the experiments. The following conclusions were mainly drawn through comparative analysis: as the axial compression ratio increases, oblique cracks are gradually formed in the parallel shear direction of the concrete, accompanied by a small amount of concrete spalling. The strain rate parameter has no significant influence on the apparent failure pattern of concrete in the parallel shear direction; moreover, as the axial compression ratio increases, the ranges of increase in shear stress and residual stress for concrete under different strain rates are 357.02% to 291.65%. The increase of strain rate gradually leads to a decreasing trend of shear stress for concrete under the influence of the axial compression ratio; as the strain rate increases, the range of increase in shear stress for concrete under different axial compression ratios is 21.08% to 33.81%. Overall, the increase of axial compression ratio leads to a decreasing trend of shear stress for concrete under the influence of strain rate. Based on the compression-shear relation and the principal stress space, the combined dynamic failure criterion of plain concrete is proposed by considering the effect of strain rate, and the corresponding stress mechanism is analyzed. The research results are of great significance to the development and application of concrete engineering.