Fracture and damage properties of high-strength concrete under cyclic loading

To study the fracture and damage characteristics of high-strength concrete (HSC), three-point bending (TPB) tests were performed on single-edged notched beams under cyclic loading, and digital image correlation (DIC) technique was used to measure the surface deformation of the beams. First, the crack mouth opening displacement (CMOD) measured by the DIC was compared with that obtained by clip gauge to verify the reli-ability of the DIC technique in measuring the surface deformation of materials. Then, the relationships between the load and displacements were studied; Finally, the impact of loading history on the CMOD, crack length (Lc), stiffness (S), dissipated energy, fracture energy (GF), strain concentration zone (SCZ) and damage zone were investigated. The experimental results indicated that the bearing capacity, deformation performance and the GF of HSC were not affected by the loading and unloading process; under cyclic loading, as the dimensionless crack mouth opening at the unloading point (CMODduni) increases, the dimensionless residual crack mouth opening (CMODdri) gradually increases while the load degradation rate (phi) gradually decreases; in the ith cycle of the post -peak stage, the crack opening rate was greater than the crack growth rate when the beam was loaded to the peak point from the reloading point. To quantify the damage degree of the single-edged notched beam, damage index (D) was calculated, which is more suitable obtained from the damage zone-based method than that calculated from the P-CMOD curve.

Automated summary

This study investigated the fracture and damage characteristics of high-strength concrete using cyclic loading and digital image correlation technique. The experimental results showed that the bearing capacity, deformation performance, and fracture energy of HSC were not affected by the loading and unloading process. Under cyclic loading, the residual crack mouth opening increased as the crack mouth opening displacement increased, while the load degradation rate decreased.