Abstract:
Based on the cohesive zone model (CZM) with mixed fracture modes, a concrete microscale analysis model can effectively describe the damage characteristics and mechanical properties of concrete structures under complex stress conditions. The application of CZM meso scale models in structural analysis is severely limited by the excessive number of element parameters and the unclear parameter effects. A parametric study is conducted to investigate the stiffness, strength, and fracture energy parameters of cohesive elements, based on the validation of the CZM microscale analysis model for standard uniaxial concrete specimens. Under axial tensile loading, the mesoscale model is mainly controlled by the Mode I fracture parameters, and the Mode II fracture parameters have limited influences. Under axial compressive loading, the microscale model is jointly controlled by Mode I and Mode II parameters. The initial stiffness of the mesoscale model is only related to the cohesive element stiffness and is almost unaffected by the strength and fracture energy parameters. The relationship between concrete strength and element stiffness is exponential, while the relationship between strength and fracture energy is mainly linear. In order to match the descending section of the axial compressive stress-strain curve of the CZM meso-model with the constitutive curve recommended by the code, it is recommended to set the Mode II fracture energy to 25 times of the Mode I fracture energy for the descending branch curve of the mesoscale model.