• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.179-186
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• 2010

The bond between steel and concrete in reinforced concrete members is essential to resist external load, but the bond mechanism in reinforced concrete beams deteriorated by steel corrosion has not been clearly known yet. Most existing researches have dealt with the bond behavior of corroded steel under monotonic loading, but scarce are researches dealing with bond behavior of corroded steel under repeated loading. This study includes the experimental investigation on the bond behavior with respect to the various degrees of steel corrosion under repeated loading. According to the test results, the bond strength of corroded steel under monotonic loading increases as the rate of steel corrosion increases unless the splitting crack occurs. The slip versus number of load cycles relation was found to be approximately linear in double logarithmic scale, not only in specimens without steel corrosion but also in specimens with steel corrosion. The test results also show that the steel corrosion does not negatively affect the bond strength of corroded steel after repeated loading unless the splitting crack occurs. But the fatigue life decreases sharply after splitting crack occurs. This research will be helpful for the realistic durability design and condition assessment of reinforced concrete structures.

• Journal of Korean Society of Steel Construction
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• v.27 no.4
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• pp.359-370
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• 2015

This paper presents the experimental results for the interfacial bond behaviour between AFRP strip and steel members. The objective of this paper is to examine the interfacial behavior and to evaluate the interfacial bond stress between Aramid FRP strips and steel plates. The test variables were bond length and AFRP thickness. 18 specimens were fabricated and one-face shear type bond tests were conducted in this study. There were two types of failure mode which were debonding and delamination between AFRP strip and steel plates. From the test, the load was increased with the increasing of bond length and AFRP thickness, which was observed that maximum increase of 63 and 86% were also achieved in load with the increasing of bond length and AFRP thickness, respectively. Finally, bond and slip characteristics had the elastic bond-slip model and it was observed that bond strength and fracture energy were not affected by bond length and AFRP thickness.

• Journal of the Korean Society for Railway
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• v.12 no.6
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• pp.944-952
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• 2009

This paper presents an analytical model for calculation of crack widths in reinforced concrete structures. The model is mathematically derived from the actual bond stress-slip relationships between the reinforcement and the surrounding concrete, and the relationships summarized in CEB-FIP Model Code 1990 and Eurocode 2 are employed in this study together with the numerical analysis result of a linear slip distribution along the interface at the stabilized cracking stage. With these, the actual strains of the steel and the concrete are integrated respectively along the embedment length between the adjacent cracks so as to obtain the difference in the axial elongation. The model is applied to the test results available in literatures, and the predicted values are shown to be in good agreement with the experimentally measured data.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.213-220
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• 2015

CFT column has a lot of structural advantages due to the composite behavior between in-filled concrete and steel tube. This paper deals with the development of an effective numerical model which can consider the bond-slip behavior between both components of concrete matrix and steel tube without taking double nodes. Since the applied axial load to in-filled concrete matrix is delivered to steel tube by the confinement effect and the friction, the governing equation related to the slip behavior can be constructed on the basis of the force equilibrium and the compatability conditions. In advance, the force and displacement relations between adjacent two nodes make it possible to express the slip behavior with the concrete nodes only. This model results in significant savings in the numerical modeling of CFT columns to take into account the effect of bond-slip. Finally, correlation studies between numerical results and experimental data are conducted to verifying the efficiency of the introduced numerical model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.409-416
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• 2019

An improved numerical model for non-linear analysis of reinforced concrete (RC) slabs subjected to blast loading is proposed. This approach considers a strain rate dependent orthotropic constitutive model that directly determines the stress state using the stress-strain relation acquired from the data obtained using the biaxial strength envelope. Moreover, the bond-slip between concrete and reinforcing steel is gradually enlarged after the occurrence of cracks and is concentrated in the plastic hinge region. The bond-slip model is introduced to consider the crack direction of the concrete under a biaxial stress state. Correlation studies between the numerical analysis and the experimental results were performed to evaluate the analytical model. The results show that the proposed model can effectively be used in dynamic analyses of reinforced concrete slab members subjected to explosive loading. Moreover, it was determined that it is important to consider biaxial behavior in the material model and the bond-slip effect.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.155-163
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• 2013

This study investigated the bond characteristics of embedded deformed steel bar in donut type biaxial hollow slabs. The donut type hollow sphere make concrete inner cover formed between steel bar and hollow sphere due to the hollow shape and arrangement. Generally, inner cover was thinner than outer cover, and some part of donut type biaxial hollow slab has smaller inner cover thickness than $2.5d_b$. It was affected to the bond condition of deformed bar. Furthermore, inner cover thickness changes along the longitudinal deformed bar due to hollow shape. Therefore, donut type hollow slab was divided 3 regions according to the hollow shape such as insufficient region, transition region, sufficient region. Pull-out test were performed to find out the effect of bond condition by the region. Main parameters are inner cover thickness, embedded length and bond location. Bond characteristics of donut type biaxial hollow slab were confirmed through comparison of bond stress-slip relationship, maximum bond strength and bond stress distribution of each regions. And the calculation method of bond strength of donut type biaxial hollow slab was suggested based on the test results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2279-2286
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• 2015

Recently it has been actively studied that the use of hybrid GFRP-concrete structure with dual purpose of both a permanent forwork and main tensile reinforcement of GFRP plank. In applying general analysis and design technique to evaluate the performance of hybrid structures with cast-in-place high strength concrete and GFRP plank, it is essential that the characteristics of the bond slip model is identified. In this study a simplified bilinear bond slip model for hybrid structure with GFRP plank and cast-in-place high strength concrete is proposed. Maximum average bond stress of simple bond slip relationship that has been proposed in this study is 3.29MPa, initial slope is 35.66MPa/mm, the total slip is 0.23mm and interfacial fracture energy is 0.37kN/m.

• Magazine of the Korea Concrete Institute
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• v.2 no.4
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• pp.99-107
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• 1990

The transfer of forces across the interface by bond between concrete and steel is of fundamentul importance to many aspects of reinforced concrete behavior. Bond stress-slip relationships were studied using a symmetri¬cal tension test specimen. This type of test is intended to simulate conditions in the tension zone of a concrete beam between primary cracks and below the neutral axis. These relationships between local bond stress and local slip are found to be quite different at different locations along the bar. The bond behavior under cyclic lo¬ading is also studied in the present study, and the increase of bond slip and steel strains is clarified from those tests.

• Magazine of the Korea Concrete Institute
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• v.4 no.3
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• pp.113-121
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• 1992

본 논문에서는 철근콘크리트 부재의 뽐힘부착거동을 규명하기 위하여 일련의 포괄적인 실험 및 이론 연구를 수행하였다. 실험의 주요변수는 콘크리트의 압축강도, 철근간격 및 덮개, 그리고 철근의 부착길이 등을 선정하였다. 본 연구결과 철근 콘크리트의 부착강도는 뿐만아니라 부착길이, 철근의 덮개 등에 따라 큰 영향을 받는 것으로 나타났으며, 본 연구에서는 이들의 영향을 정량적으로 도출하였다. 또한, 본 연구에서는 철근콘크리트의 부착강도식을 새롭게 제안하였으며, 부착응력-슬립관계식도 유도하여 제시하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.517-528
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• 2008

This paper presents a hysteretic damage model for reinforced concrete (RC) joints that explicitly accounts for the bond-slip between the reinforcing bars and the surrounding concrete. A frame element whose displacement fields for the concrete and the reinforcing bars are different to permit slip is developed. From the fiber section concept, compatibility equations for concrete, rebar, and bond are defined. Modification of the hysteretic stress-strain curve of steel is conducted for partial unloading and reloading conditions. Local bond stress-slip relations for monotonic loads are updated at each slip reversal according to the damage factor. The numerical applications of the reinforcing bar embedded in the confined concrete block, the RC column anchored in the foundation, and the RC beam-column subassemblage validate the model accuracy and show how including the effects of bond-slip leads to a good assessment of the amount of energy dissipation during loading histories.