Engineering Fracture Mechanics. Vol. 75, No. 13, pp. 3806-3818, 2008.
K. Park, G.H. Paulino and J.R. Roesler
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Newmark Laboratory, 205 North Mathews Avenue, IL 61801, USA
The cohesive zone model (CZM) characterizes non-linear concrete fracture behavior through a bi-linear softening curve. The features of the bi-linear softening curve are essential for predictions of concrete fracture. However, there is no agreement about the location of the kink point in the bi-linear softening curve. In this study, the location of the kink point is proposed to be the stress at the critical crack tip opening displacement. All fracture parameters required to describe the bi-linear softening curve can be determined with the two-parameter fracture model and the total work of fracture method based on a single concrete fracture specimen. The proposed location of the kink point compares well with the range of kink points reported in the literature, and is verified by plotting stress profiles along the cohesive zone in numerical simulations. Finally, prediction of experimental load versus crack mouth opening displacement curves, through numerical simulation with an intrinsic tri-linear CZM, validates the proposed location of the kink point.
KEY WORDS: Bi-linear softening, Kink point, Cohesive zone model (CZM), Two-parameter fracture model (TPFM).