The fracture extreme theory for determining the effective fracture toughness and tensile strength of concrete

A theoretical method for determining the effective fracture toughness KICe and tensile strength ft of concrete was proposed based on the fictitious crack model. With the fracture extreme theory (FET), only the experimental peak load of one specimen in fracture test is required for the calculation. The application of the proposed method was illustrated by the three-point bending notched concrete beam. The KICe, ft, critical crack tip opening displacement CTODc, and critical crack propagation length Δac of beams with different initial notch ratio a0/h were obtained. The results obtained by the proposed method were in good agreement with those by the experimental data and existing analytical method, which confirmed its applicability. And the calculated values of KICe are insensitive to a0/h using the proposed method.