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Advances in Materials Science and Engineering
Volume 2014 (2014), Article ID 683756, 12 pages
http://dx.doi.org/10.1155/2014/683756
Research Article

Crack Extension Resistance of Normal-Strength Concrete Subjected to Elevated Temperatures

College of Civil Engineering, Tongji University, Shanghai 200092, China

Received 5 March 2014; Revised 29 May 2014; Accepted 30 May 2014; Published 26 June 2014

Academic Editor: Juan José del Coz Díaz

Copyright © 2014 Jing Chen and Zhoudao Lu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Determination of the residual crack extension resistance curves ( -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  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 ( -curves) are calculated. In each temperature, with the distribution of cohesive force along the fracture process zone, the residual fracture toughness ( ) increases with increasing crack length , whereas the -curves decrease with increasing temperatures for the thermal damage induced. The stability analysis on crack propagation demonstrates that when the residual -curve is higher than -curve, the crack propagates steadily; otherwise, the crack propagates unsteadily.