• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.635-638
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• 2004

External bonding of steel plates has been used to strengthen deficient reinforced-concrete structures since the 1960s. In recent years, fiber-reinforcde polymer(FRP) plates have been increasingly used to replace steel plates due to their superior properties. This paper is concerned with anchorage failure due to crack propagation parallel to the boned plated near or along the adhesive/concrete interface, staring from the critically stressed position toward the anchored end of the plates. Factor of bond-slip interface model is average bond stress, effective length, slip volume and fracture energy. The aim of the present paper is to provide a comprehensive assessment of bond-slip interface model with concrete and CFRP plates.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1132-1141
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• 2019

Steel-concrete-steel (SCS) sandwich structures have important advantages over conventional concrete structures, however, bond-slip between the steel plate and concrete may lead to a loss of composite action, resulting in a reduction of stiffness and fatigue life of SCS sandwich structures. Due to the inaccessibility and invisibility of the interface, the interfacial performance monitoring and debonding detection using traditional measurement methods, such as relative displacement between the steel plate and core concrete, have proved challenging. In this work, two methods using piezoelectric transducers are proposed to detect the bond-slip between steel plate and core concrete during the test of the beam. The first one is acoustic emission (AE) method, which can detect the dynamic process of bond-slip. AE signals can be detected when initial micro cracks form and indicate the damage severity, types and locations. The second is electromechanical impedance (EMI) method, which can be used to evaluate the damage due to bond-slip through comparing with the reference data in static state, even if the bond-slip is invisible and suspends. In this work, the experiment is implemented to demonstrate the bond-slip monitoring using above methods. Experimental results and further analysis show the validity and unique advantage of the proposed methods.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.385-390
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• 2001

This paper presents a nonlinear analysis technique with slip, the effects of slip modulus and composite action by shear connector on behavior and capacity in composite structure of sandwich system. As a results of this study, it proved that the slip modulus, in case of shear behavior, seldom influence load-resistance capacity such as yield and ultimate load, but in case of flexural behavior, it appropriately influence load-resistance capacity because of stress redistribution by slip. In case of flexural behavior, analysis result for perfect-composite results in over-estimation and perfect-slip results in under-estimation on behavior and capacity. Therefore, it is desirable to model steel-concrete interface with partial-composite. The effects of slip on behavior and capacity are less in case of positive composite than loosely composite, and it proved that composite action by shear connector improve the load-resistance capacity of this system.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.113-116
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• 2006

In this study, new bond-slip model is proposed. The proposed bond-slip model which has bilinear ascending regions and exponential descending region by modifying the conventional bilinear bond-slip model has been verified. Then, result by finite element analyses using interface element implemented with bond-slip model compared well with those of existing experiment researches on bond-slip models. It is shown that bond strength and effective bond length predicted by the bond-slip model and finite element analysis is good agreement with those of pull tests.

• Structural Engineering and Mechanics
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• 제74권5호
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• pp.589-600
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• 2020

The bonding interface of the concrete slab track and cement-asphalt mortar layer plays an important role in transferring load and restraining the track slab's deformation for slab track structures without concrete bollards in high-speed railway. However, the interfacial bond-slip behavior is seldom considered in the structural analysis; no credible constitutive model has been presented until now. Elaborating the field tests of concrete to cement-asphalt mortar interface subjected to longitudinal and transverse shear loads, this paper revealed its bond capacity and failure characteristics. Interfacial fractures all happen on the contact surface of the concrete track slab and mortar-layer in the experiments. Aiming at this failure mechanism, an interfacial mechanical model that employed the bilinear local bond-slip law was established. Then, the interfacial shear stresses of different loading stages and the load-displacement response were derived. By ensuring that the theoretical load-displacement curve is consistent with the experiment result, an interfacial bond-slip constitutive model including its the corresponding parameters was proposed in this paper. Additionally, a finite element model was used to validate this constitutive model further. The constitutive model presented in this paper can be used to describe the real interfacial bonding effect of slab track structures with similar materials under shear loads.

• 콘크리트학회논문집
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• 제20권4호
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• pp.477-486
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• 2008

탄소섬유시트 보강공법은 콘크리트구조물의 보강에 많이 사용되는 보강공법이다. 이러한 탄소섬유 보강공법에서는 콘크리트와 CFRP시트 사이의 경계면 거동이 전체 보강구조물의 거동을 지배하게 된다. 본 연구에서는 탄소섬유시트 보강공법을 적용한 콘크리트구조물의 경계면 거동에 대한 기존의 연구들을 고찰하고, 이를 바탕으로 경계면 부착거동해석에 효과적으로 사용될 수 있는 새로운 bond-slip model을 제시하고, 경계면의 부착거동을 해석할 수 있는 해석 기법을 제안하였다. 새롭게 제시된 bond-slip model은 기존의 bilinear bond-slip model을 개선한 것으로서, 전단응력이 증가하는 구간을 2개의 직선구간으로 구성하고, 전단응력이 감소하는 구간을 지수함수로 구성한 것이다. 제안된 bond-slip model은 기존의 부착전단 실험 결과 및 경계면 거동 모델들과의 비교를 통하여 검증하였다.

• 한국지반공학회논문집
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• 제19권4호
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• pp.265-275
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• 2003

본 연구에서는 매립지에서 사용되고 있는 토목섬유 (지오멤브레인, 지오텍스타일, 토목섬유 점토 차수재) 사이의 동적 접촉 마찰 특성을 평가하기 위해서 진동대 실험을 실시하였다. 동적 하중하에서 진동대와 하부에 토목섬유가 부착된 상자의 가속도, 이들 사이의 상대적 변위를 측정하였으며, 연직응력, 진동 주파수, 건조/수침 상태가 접촉면의 동적 거동 특성에 미치는 영향도 알아보았다. 실험 결과를 통해 동적하중이 감쇠없이 토목섬유 사이를 통과하는 한계 가속도가 존재함을 확인하였으며, 이를 이용하여 토목섬유 사이의 동적 접촉 마찰각을 산정할 수 있었다. 접촉면에서의 상대 변위는 접촉면의 형태와 건조/수침 상태에 따라 다르게 측정되었다. 각 토목섬유 접촉면에 대한 최대 상대변위는 무차원으로 정규화시켜, 가속도와 최대 미끄러짐 사이의 관계식을 구하였다. 이 식을 이용하면 주어진 가속도와 주파수에서, 토목섬유 사이를 따라 발생되는 최대 미끄러짐의 크기를 예측할 수 있다.

• Computers and Concrete
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• 제24권2호
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• pp.173-183
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• 2019

This study presents experimental and numerical results of prestressed concrete composite beams with different casting and stressing sequence. The beams were tested under three-point bending and it was found that prestressed concrete composite beams could not achieve monolith behavior due to interface slippage between two layers. The initial stress distribution due to different construction sequence has little effect on the maximum load of composite beams. The multi-step FE analyses could simulate different casting and stressing sequence thus correctly capturing the initial stress distribution induced by staged construction. Three contact algorithms were considered for interaction between concrete layers in the FE models namely tie constraint, cohesive contact and surface-to-surface contact. It was found that both cohesive contact and surface-to-surface contact could simulate the interface slip even though each algorithm considers different shear transfer mechanism. The use of surface-to-surface contact for beams with more than 2 layers of concrete is not recommended as it underestimates the maximum load in this study.

• Steel and Composite Structures
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• 제20권5호
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• pp.1023-1042
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• 2016

Based on Hamilton's principle, the flexural vibration differential equations and boundary conditions of the steel-concrete composite beam (SCCB) with comprehensive consideration of the influences of the shear deformation, interface slip and longitudinal inertia of motion were derived. The analytical natural frequencies of flexural vibration were compared with available results previously observed by the experiments, the results calculated by the FE model and the other similar beam theories available in the open literatures. The comparison results showed that, the calculation results of the analytical and Timoshenko models had a good agreement with the results of the experimental test and FE model. Finally, the influences of shear deformation and interface slip on the flexural natural frequencies of the SCCB were discussed. The shear deformation effect increases with the increase of the mode orders of flexural natural vibration, and the flexural natural frequencies of the higher mode orders ignoring the influence of shear deformations effect would be overestimated. The interface slip effect decrease with the increase of the mode orders of flexural natural vibration, and the influence of the interface slip effect on flexural natural frequencies of the low mode orders is significant. The influence of the degree of shear connection on shear deformation effect is insignificant, and the low order modes of flexural natural vibration are mainly composed of the rotational displacement of cross sections.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제23회 학술대회
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• pp.1-3
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• 1996

The characteristics of fretting wear are reviewed. Fretting damage depends on slip amplitude and classified into three groups: (1) an annular damage according to Mindlin's analysis at microslip region, (2) strong adhesive deformation without loose wear particles at the intermediate region, and (3) formation of fine oxide particles at the gross slip region. The critical slip amplitude of fretting is the boundary between (2) and (3). The boundary slip amplitude depends on normal load. The wear rate increases and saturates with increasing slip amplitude. But it is constant by considering the critical amplitude. The role of oxide particles are discussed. Three different actions are noted: accelerating wear, preventing wear and insignificant effect. The oxide shows two opposing effect depends on normal load and slip amplitude. This is related to the removal rate from the interface (abrasive action) and compaction rate at the interface to form a protective layer. The effect of oxidation is significant to determine the wear and friction. The diffusion of oxygen is restricted at the small amplitude. As a result, crack formation at the boundary is a predominant damage, related to fretting fatigue damage.