Influence of hole geometry and fiber content on crack and displacement in concrete under cyclic loading

The crack trajectory in concrete specimens is a critical factor in characterizing structural failure. Due to the heterogeneous nature of concrete, the presence of asymmetric holes can disrupt uniformity within structural members. Asymmetry, non-uniformity, and variable loading further complicate the behavior of concrete components. This study involved the fabrication of 144 standard 150 mm cubic specimens with four different mix designs, containing fiber content at fractions of 0%, 8%, 16%, and 24%. The specimens had square, rectangular, and triangular holes, to evaluate the effects of holes geometry and asymmetry on concrete behavior. A numerical model was developed using VariCAD and analyzed with SimSolid. The specimens were subjected to five cycles of cyclic loading. Results showed that internal displacement was lower than external displacement under cyclic loading. Symmetric holes positioned at the center of the concrete had no significant effect on external displacement, whereas asymmetric holes increased maximum displacement at the corners. The length, width, and depth of the specimens influenced the areas of maximum displacement. The addition of fibers had a pronounced effect on internal displacement, shifting the maximum displacement and crack trajectory towards the corners in specimens with holes. Cyclic loading of specimens with different hole shapes revealed that crack initiation depended on the positions and conditions of holes. This finding was further supported by modeling of maximum displacement. Specimens with holes exhibited larger ultimate strain compared to those without holes.