Bond-strengthening Hooks For Rc Members With 1300 Mpa-class Shear-reinforcing Spirals Part Iii: Bond Strengths Of Double-layered Longitudinal Bars And Cut-off Bars

摘要

This paper presents an experimental investigation of reinforced concrete (RC) beams with double layered longitudinal bars, bond-strengthening hooks and 1300 MPa-class spirals. The hooks made of mild steel increased the bond strength along longitudinal bars. This experiment is aimed at quantification of not only the effectiveness of the spirals and bond-strengthening hooks on the RC members consisting of double layered longitudinal bars but also the influence of cut-off bars in an inner (second) layer. Twelve specimens were prepared and subjected to cyclic shear loads. All the specimens failed because of bond splitting along the longitudinal bars. The hooks, made of mild steel, increased the bond strength along the longitudinal bars. Applying the bond-strengthening hooks was found to improve the shear capacities of the specimens with the cut-off bars. The authors developed a truss mechanism model for members with longitudinal bars in an inner (second) layer. The model showed that the shear strength depends on the span/depth ratio L/D and inner (second) layer bar length L_d.