Crack extension resistance of normal-strength concrete subjected to elevated temperatures

Abstract

Determination of the residual crack extension resistance curves (K R -curves) associated with cohesive force distribution on fictitious crack zone of complete fracture process is implemented in present research. The cohesive force distributes according to bilinear softening traction-separation law proposed by Petersson. Totally ten temperatures varying from 20°C to 600°C and the specimen size of 230 × 200 × 200 mm with initial-notch depth ratios 0.4 are considered. The load-crack mouth opening displacement curves (P-CMOD) of postfire specimens are obtained by wedge-splitting method from which the stress intensity factor curves (K -curves) are calculated. In each temperature, with the distribution of cohesive force along the fracture process zone, the residual fracture toughness K R (Δ a) increases with increasing crack length Δ a, whereas the K R -curves decrease with increasing temperatures T m for the thermal damage induced. The stability analysis on crack propagation demonstrates that when the residual K R -curve is higher than K -curve, the crack propagates steadily; otherwise, the crack propagates unsteadily. © 2014 Jing Chen and Zhoudao Lu.