Experimental Study On Concrete Two-parameter Model And The Double-k Fracture Criterion

With the development of structural analysis and design methods, the study on the fracture behavior of concrete has been widely taken seriously. Focusing on the Two Parameter Fracture Method and the double-Kcriterion, the following work is carried on in this paper.1. Study on the TPFM and double-K in theory and determining parameters and experiment method. Results show that the TPFM and double-K based linear elastic fracture mechanic described the fracture behavior of concrete through some different hypothesis and explanation for the phenomenon of non-linearity, that the TPFM based on the effective crack length ac and the double-K based on the fictitious crack model, that The TPFM does not show the reliance of the bilinear softening traction-separation law and the fracture behavior of material, but the double-K can , that the testing procedure of double-K is rather simple without unloading and reloading procedures.2.The explanation of cause of non-linear feature in P-CMOD curve leads to the difference in the methods of calculating the effective crack length ac. Yet, in the double-K, it can predict the initiation and stable and unstable fracture of concrete structures.3.By using the three-point bending beam of which dimensions are 800X200X200 (SX h X f) with ratio of the initial crack length ao against h are 0.2,0.3 , 0.4, 0.5, 0.6 test, to study the difference in the methods of calculating the effective crack length ac. Results show that the effective crack length ac calculated by the TPFM is shorter than which of the double-AT. The K/c based on the initial ao/h is not influenced by ao/h.4. By using the wedging splitting specimens of which dimensions are 200 X 200 X 200 (SX hXf) with ratio of the initial crack length a0 against h are 0.2, 0.3 , 0.4, 0.5, 0.6 test, to study the difference in the methods of calculating the effective crack length ac. Results show that the effective crack length ac calculated by the TPFM is shorter than which of the double-K The KJC based on the initial ao/h is influenced by ao/h.According to the results of ac can infer that the KIC calculated by the TPFM is shorter than the KKm calculated by the double-K.