Mode I Fracture in Concrete Using Center‐Cracked Plate Specimens

Many have attempted to quantify the fracture toughness of concrete using linear elastic fracture mechanics (LEFM). It has been observed that critical mode I stress intensity factor, $K_{\mathrm{Ic}}\text{,}$ calculated by substitution of measured peak load and initial notch length in the LEFM formulas, is size‐ and geometry‐dependent. In this paper, the mode I fracture of concrete is studied using center‐cracked plate specimens with a point load applied at the center of the crack. A special clip gage was developed to measure the crack opening displacement (COD). The results were analyzed using the measured load‐COD response of the specimen. This investigation confirms that conventional LEFM is not applicable to concrete and that the use of an effective crack length approach based on compliance calibration may be more appropriate for analyzing the nonlinear response of concrete.