The effect of concrete material parameters on the concrete initial stress intensity factor on the fracture parameter

SUMMARYTHE EFFECT OF CONCRETE MATERIAL PARAMETERS ON THE CONCRETE INITIAL STRESS INTENSITY FACTOR ON THE FRACTURE PARAMETERApplications of LEFM to concrete were initiated by Kaplan in 1961 and continued until Kesler and co-workers? study in 1972 in which it was concluded that LEFM was not valid for cementitious materials. This inapplicability of LEFM is due to the fracture process zone (FPZ) which is ignored by LEFM. For this reason, several investigators have developed non-linear fracture mechanics approaches to characterize FPZ. These approaches primarily involve the TPM and the ECM. Contrary to LEFM, in which a single fracture parameter is used such as the critical stress intensity factor, these models need at least two experimentally determined fracture parameters to characterize failure of concrete structures.Experimental studies have shown that fracture parameters of concrete are particularly influenced by the four material parameters compressive strength, maximum aggregate size, water-cement ratio and aggregate type. It is noted that fracture parameters of concrete can also be affected by other material parameters such as type of cement, cement content.To characterize failure of concrete structures, the Double-K Model needs two fracture parameters: the unstable stress intensity factor and the initiation stress intensity factor . Nevertheless, the parameter is calculated by using the cohesive stress intensity factor which is based on some empirical expressions in CEB-FIB Code. To determine , an alternative analytic approach used in this paper and based on the experimental studies made for EÇM, it is intended to build a relationship between material parameters and fracture parameters ( , ).Keywords: Concrete, Fracture Mechanics, Effective Crack Model, Linear Elastic Fracture Mechanics, Crack.