Calculating crack extension resistance of concrete based on a new crack propagation criterion

A crack propagation criterion was proposed for model I crack in concrete by using the initial fracture toughness K-IC(ini) as an inherent material property. Based on this criterion, crack begins to propagate when the difference, between the stress intensity factors caused by the applied load K-I(P) and that by the cohesive stress K-I(sigma), K-IC(ini). Finite element analyses was then carried out to calculate the complete load vs. crack mouth opening displacement (P-CMOD) curve, the critical crack propagation length Delta a(c) and the unstable fracture toughness K-IC(un) for notched beams under three-point bending. It was found that numerical results showed a good agreement with the experimental ones. Based on this crack propagation criterion, crack extension resistance, in terms of stress intensity factor. K-R being able to consider the variation of fracture process zone (FPZ) was employed for describing crack propagation in concrete. K-R is composed of K-IC(ini) and K-I(sigma), which is actually equal to the driving action of crack extension. It was concluded that given the elastic modulus E, the uniaxial tensile strength f(t), the fracture energy G(F) and K-IC(ini), the complete fracture process in concrete and the K-R-curve of concrete can be calculated based on the numerical method. Finally, discussion was made on the effects of fracture process zone, G(F) and specimens geometries on K-R-curve. (C) 2012 Elsevier Ltd. All rights reserved.