• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.2
• /
• pp.38-46
• /
• 2014

Effects of various parameters on bond property between reinforcing bar and concrete are investigated in many researchers, and various study is on going to improve the bond strength. Properties of interface between reinforcement and concrete is important role in bond property. This study analyzed the interfacial bond mechanism between deformed bar and concrete by finite element analysis (FEA) to evaluate the effect of rib shape. The FEA model in this study is simplified 2D plane stress model. The variables of analysis are selected by rib angle, rib height, rib spacing and relative rib area. From the results of analysis, reinforcing bars with rib angle $30{\sim}60^{\circ}$ showed better bond strength than the others. Bond strength ratio following to the rib height is proportionally increased up to the $0.12d_b$, but rib spacing has little effect on bond strength. The results also indicated that relative rib area can be efficiently represented the properties of deformed shape in reinforcing bars, and zigzagged rib height shape showed excellent bond strength increase.

• Journal of the Korea Concrete Institute
• /
• v.15 no.1
• /
• pp.17-24
• /
• 2003

One of the reasons for brittle failure in reinforced concrete structures subjected to severe earthquake is due to large local bond-slippage of bars resulting in fast bond degradation between reinforcing bars and concrete. This study aims to evaluate effects of bar deformation height on bond performance, specially, bond degradation under cyclic loading. Bond test specimens were constructed with machined bars with high relative rib areas. The degree of confinement by transverse bars is also another key parameters in this bond test. From test results, amounts of energy dissipation are calculated and compared for each parameter. Test results show that bond strength and stiffness drops significantly as cycles increases. The confinement and high relative rib area are effective to delay bond degradation, as the reduction of bond strength of cyclic loading compared to monotonic loading decreased for bars with large confinement and high relative rib areas. The energy dissipation also increases as the degree of confinement and relative rib area increases. However, tested bars with very high rib areas show that the bond may be damaged at relatively small slip because of high stiffness. The study will help to understand the bond degradation mechanism due to bar deformation height under cyclic loading and be useful to develop new deformed bars with high relative rib areas.

• Journal of the Korea Concrete Institute
• /
• v.13 no.3
• /
• pp.244-250
• /
• 2001

One of the reasons for brittle failure in reinforced concrete structures subjected to severe earthquake is due to large slip between reinforcing steel and concrete. This study aims to evaluate effects of deformation patterns of ribbed reinforcing bars on bond under cyclic loading. Bond test specimens were constructed with machined bars to test the newly developed reinforcing bars with high relative rib areas. The degree of confinement is also another key parameter in this bond test. From the test results under monotonic and cyclic loading, bond strength and stiffness were evaluated. Bond strength and bond stiffness increase as relative rib areas under cyclic loading for specimens highly confined by transverse reinforcement. The increase rates of the bond performance under cyclic loading are larger than those of specimens under monotonic loading. The developed bars with high relative rib areas will contribute for better bond performance for reinforced concrete structures subjected to severe seismic loadings.

• Journal of the Korea Concrete Institute
• /
• v.17 no.3 s.87
• /
• pp.375-384
• /
• 2005

The effects of bar deformation properties on bond of steel reinforcing bars to concrete are experimentally studied to predict the bond strength. Based on the previous research about high relative rib area, bond strength between reinforcing bars and concrete can be improved by the control of rib height and spacing. But, the equations in Korean code provisions to estimate development and splice length do not include these specifications of reinforcing bars. So the purpose of this paper is to determine the effect of relative rib area to the bond strength. This paper describes 2 kinds of experimental researches. Thirty beam-end specimens were tested to investigate the effects of bar size and relative rib areas ranging from 0.112 to 0.162. And, twelve lap-splice beam specimens were tested to the same variables. Each test results are normalized and compared with the proposed equations of ACI 408 committee. The results show that bond strength is increased as bar size and the relative rib area(Rr) increase. The distribution of flexural cracks and failure aspect do not appear to be affected by $R_r$.