QUASI-BRITTLE FRACTURE MODEL AND APPLICATION ON CONCRETE CONSIDERING AGGREGATE VOLUME CONTENT EFFECT

Based on the analysis of parameters in a Boundary Effect Model, the average aggregate size d_ave has been introduced into the model. Whereafter, the quasi-brittle fracture prediction model on concrete considering aggregate volume content and size effect has been proposed. The ratio of effective notch length to characteristic crack length in this model can clarify the fracture failure criterion of the specimens as the variation of the dimension and initial notch length for single edge notched beams (SENB) in three-point-bending tests. The fictitious crack length in critical crack growth region at P_max will be determined by the d_ave and dispersion coefficient β_ave in this model. Based on the stress analysis of the SENB at P_max, the relationship between critical nominal strength σ_n and effective notch length ae and tensile strength f_t and fracture toughness K_IC has been obtained. According to the experiment results performed by Amparano, the tensile strength and fracture toughness could be predicted well by the fracture model with the average fictitious crack length Δa_fic=(0.8~1.4)d_ave. The reliability and applicability of the fracture model proposed have been confirmed by the comparison of the prediction curves derived by the fracture model at Δa_fic=1.2 d_ave with the experiment results. According to the three-point-bending tests with SENB proposed by RILEM, tensile strength and fracture toughness can be predicted by the quasi-brittle fracture prediction model on concrete considering aggregate volume content effect.