A PRACTICAL ANALYTICAL APPROACH TO THE DETERMINATION OF DOUBLE-K FRACTURE PARAMETERS OF CONCRETE

Using the standard three-point bending beam specimens, the precritical crack propagation length caD was evaluated from the maximum load maxP and the corresponding critical crack mouth opening displacement (CMODc) was measured in experiments. A practical analytical method is proposed for determining the stress intensity factor cKI caused by the cohesive force )(xs along the fictitious crack zone, thereby, the double-K fracture parameters iniKIC and unKIC are determined. With this method the double-K fracture parameters iniKIC and unKIC can be easily determined using the measured maxP, CMODc, elastic module E, and tensile strength tf of a concrete material, and the numerical integration can be avoided for the calculation of cKI. Many calculations and analyses show that the newly proposed method is of high accuracy and of significance to draw up the standard testing method for the double-K fracture parameters of concrete.