Experimental Investigation of the Dynamic Mechanical Properties of Concrete under Different Strain Rates and Cyclic Loading

To investigate the effects of strain rate and cyclic loading on the mechanical parameters of concrete compressive strength, residual strain, peak strain and elastic modulus, a series of cyclic loading tests over concrete were conducted by setting different numbers of cycles, magnitude factors, and cycle frequencies/periods based on the FST-1000 alpine geotechnical dynamic and static triaxial test system. The quantitative relationships between the mechanical parameters of concrete and the parameters of cyclic loading as well as the strain rate were also proposed. The results show that as the strain rate increases, the concrete compressive strength and elastic modulus increase linearly, while the residual strength and peak strain show a decreasing trend. Under cyclic loading, the compressive strength was quadratically related to each cyclic loading parameter, and the elastic modulus was quadratically related to the cyclic number and magnitude factor. The trend of the concrete compressive strength rate sensitivity undergoes a change at the specific thresholds of 0.145 for the magnitude factor and 1.93 Hz for the frequency. The minimum value of the peak strain rate sensitivity corresponds to the specific thresholds of 6023 for the number of cycles, 0.14 for the magnitude factor, and 1.38 Hz for the frequency thresholds, respectively. Additionally, the enhancement of the elastic modulus rate sensitivity occurs when the number of cycles exceeds 918 or when the magnitude factor surpasses 0.33. The results can provide a theoretical basis for the design of concrete structures and seismic engineering.