Effect of large crack–depth ratio on three-point bending concrete beam with single edge notch

Abstract

There are three stages in the crack propagation process of concrete. They are crack initiation, crack stable propagation and crack unstable fracture. Double-K fracture model describes the three stages quantitatively. The crack–depth ratio is mainly set at 0·2–0·6 in existing studies of double-K fracture parameters. In this paper, combined with test verification, the extended finite element method is adopted to study the variation of three-point bending concrete beam with the crack–depth ratio from 0·2 to 0·85. The results shows that when the crack–depth ratio α0 > 0.6, variation of concrete beam fracture parameters is different from that with small crack–depth ratio, and the double-K fracture parameters cannot be considered as constant any more. The fracture energy, fracture toughness decrease sharply; the concrete beam has the best toughness when 0.6 ≤ α0 ≤ 0.7; and concrete beam becomes completely brittle when α0 > 0.8.