An analytical study on interactions of artificial cracks and holes contributing to increases in the shear strengths of RC beams

This study investigated the effects of cracks along rebars in reinforced concrete (RC) beams with multiple holes inside the shear spans mainly based on nonlinear finite element (FE) analyses. The analytical parameters were the hole positions that increased the shear strengths of RC beams in static loading experiments, the crack positions, and the widths. As a result of the analyses, for beams with holes arranged from near the loading points toward the positions of tensile rebars at the mid-shear span with no stirrups, when the beams had a horizontal crack, the strengths increased to the flexural capacities. However, when the beam had vertical cracks, the strength decreased to 80% for beams without holes. Meanwhile, for beams with holes arranged from the bottom side of the loading points toward the mid-height with no stirrups, the strength increased to between 110% and 160% compared with beams without holes regardless of the crack positions. Moreover, the shear behaviors of the beams did not change when the equivalent crack width exceeded 0.3 mm for each case, and changes in the behaviors of beams with stirrups were negligibly small regardless of the hole positions. It was made clear that changes in the behaviors were caused by the contributions of arch mechanisms enhanced by localizations and expansions of the minimum principal stress distributions owing to the multiple holes.