Boundary effect on concrete fracture and non-constant fracture energy distribution |
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Authors: | Kai Duan Xiaozhi Hu |
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Affiliation: | a School of Mechanical Engineering, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia b Institute for Building Materials, Swiss Federal Institute of Technology, CH-8093 Zürich, Switzerland |
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Abstract: | This paper extends the local fracture energy concept of Hu and Wittmann 29] and 30], and proposes a bilinear model for boundary or size effect on the fracture properties of cementitious materials. The bilinear function used to approximate the non-constant local fracture energy distribution along a ligament is based on the assumption of the proportionality of the local fracture energy to the fracture process zone (FPZ) height and characterises the FPZ height reduction when approaching a specimen back boundary. The bilinear function consists of a horizontal straight line of the intrinsic fracture energy GF and a declining straight line that reduces to zero at the back boundary. It is demonstrated that using the bilinear model, the size-independent fracture energy GF can be estimated from the fracture energy data measured on laboratory-size specimens, and the intersection of these two linear functions, defined as the transition ligament, represents the influence of the back boundary on the fracture properties. It is also demonstrated that the specimen size alone is not sufficient to characterise the size effect in the fracture properties observed on laboratory-size specimens. |
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Keywords: | Fracture energy Local fracture energy Boundary effect Size effect Fracture process zone Crack Ligament |
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