• Journal of the Korean Geosynthetics Society
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• v.17 no.2
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• pp.33-40
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• 2018

Characteristics of interface friction between cohesionless soils and geotechnical structure surfaces play an important role in the analysis of earth load and resistance on the structure. In general, geotechnical structures are mainly composed of either steel or concrete, and their surface roughnesses with respect to soil particle sizes influence the interface characteristics between soils and the structures. Accurate assessment of the interface friction characteristics between soils and structures is important to ensure the safety of geotechnical structures, such as mechanically stabilized earth walls reinforced with inextensible reinforcements, piles embedded into soils, retaining wall backfilled with soils. In this study, based on the database of high quality interface friction tests between frictional soils and solid surfaces from literature, equation representing peak interface friction angle is proposed. The influential factors of the peak interface friction angle are relative roughness between soil and solid surface, relative density of frictional soil, and residual (constant volume) interface friction angle. Futhermore, for the developed equation of the interface friction angle, its uncertainty was assessed statistically based on Goodness-of-fit test results.

• Magazine of the Korea Concrete Institute
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• v.10 no.3
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• pp.185-196
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• 1998

이 논문은 직사각형 단면을 갖는 철근콘크리트 보에서 휨전단균열(Flexural-Shear Crack)이 원인을 규명하기 위해 모두 16개의 보를 실험한 결과를 기술한 것이다. 실험에 이용된 콘크리트보는 전단균열에 영향을 준다고 생각되는 몇 가지 요소를 인위적으로 소거 도는 고립되도록 특수하게 제작된 것이다. 이러한 특수보의 실험결과를 같은 재원을 갖는 보통의 정상보의 결과와 직접 비교하여서 그 차이를 분석함으로써 휨전단 균열의 발생원인을 규명하였다. 그 결과, 일반적인 콘크리트보에서의 휨전단균열 발생은 철근과 콘크리트의 경계면의 부착현상과 매우 밀접한 관련이 있는 것으로 나타났다. 또한 발생된 휨전단균열의 안정성은 주철근을 따라 발생되는 수평균열의 크기에 직접적인 영향을 받고 있는 것으로 나타났다. 본 연구에서 나타난 몇 가지 사실은 현재 사용중인 전단설계규준의 근본을 이루는 전단 위험단면개념과는 상반되는 것도 있었다. 실험에서 알아낸 사실을 근거로 전단파괴기구에 대한 새로운 가설을 제안하였다. 이 새 가설은 지금까지 잘 설명되지 않은 휨전단균열의 발생과 진행에 대한 원인 및 과정을 상당히 잘 설명해주고 있다고 생각된다.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.4
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• pp.39-49
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• 2001

In this paper, inelastic analysis procedures are presented for the seismic performance evaluation of RC bridge piers with premature termination of main reinforcement. The mechanical characteristic of cracked concrete and reinforcing bar in concrete has been modeled, considering the bond effect between reinforcing bars and concrete, the effect of aggregate interlocking at crack surface and the stiffness degradation after the crack. The smeared crack approach is incorporated. In boundary plane at which each member with different thickness is connected, local discontinuous deformation due to the abrupt change in their stiffness can be taken into account by introducing interface element. The increase of concrete strength due to the lateral confining reinforcement has been also taken into account to model the confined concrete. The proposed numerical method for seismic performance evaluation of RC bridge piers with premature termination of main reinforcement will be verified by comparison with reliable experimental results.

• Journal of the Korean Geotechnical Society
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• v.26 no.11
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• pp.111-123
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• 2010

The steel pipe of steel-concrete composite drilled shafts increases the pile strength and induces the ductile failure by constraining the deformation of the inner concrete. In this research, pile loading tests were performed to analyze the field applicability of a steel-concrete composite drilled shafts. The test ground consisted of 5~7 m thick soil underlying rock mass. The test piles consisted of two steel-concrete composite drilled shafts, which were the concrete filled steel pipe piles with the diameter of 0.508 m, and a concrete pile with the same diameter. The test results showed that the boundary between the upper steel composite section and the lower concrete section was structurally weak and needs to be reinforced by using a inner steel cage. If the boundary is located in deep depth, which is not influenced by lateral load, the allowable strength of the lower concrete section increases, so an economical design can be performed by increasing the design load of steel-concrete composite drilled shafts.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.129-134
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• 1991

The effects of water-cement ratio, age, and admixture such as fly ash, silica fume on the bond strength between aggregate and mortar were investigated. As the result, with increasing of water-cement ratio, the bond strength was slightly decreased while the compressive strengths of mortar and concrete were seriously decreased. The rate of strength gain of bond strength was not decreased with increasing of water-cement ratio while that of compressive strength was gradually decreased.

• Computational Structural Engineering
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• v.8 no.2
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• pp.73-84
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• 1995

The study summarized in this paper is concerned with the buckling of longitudinal bars in reinforced concrete columns with numerical analysis method. The objectives of this study are (1) to investigate the stress transfer mechanism between concrete and reinforcement and (2) to propose a modeling equation. The results give an acceptable agreement between the proposed modeling equation and published computer packages as follows; (1) the proposed equation is a possible of strain softening of concrete and buckling of reinforcement. (2) the buckling of longitudinal bar is mainly influenced by spacing of hoop and location of the bar

• Magazine of the Korea Concrete Institute
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• v.3 no.3
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• pp.121-128
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• 1991

Thicknesses of the hase concrete blocks supportmg large machmes were estimated by analyzing the res- 0 ¬nance modes of mechanical Vibrations The vibration was produced by the mechanical impact with steel ball drop and detected by a wideband comcal piezoelectric transducei. The detected signals were analyzed by FFT and thicknesses of specimen were determined by the resonant frequency of vibratIon. For the layered concrete block, the estimated thickness is dependent on the acoustic reflective index at the boundary between layers. The estimated thickness up to 100em were in goo:l agreement with the real value. In additlOn. this technique could be applicable to the estimation of the bondmg status of the layered structures.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.645-652
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• 2002

This paper presents the flexural behavior and strengthening effect of reinforced concrete beams bonded with carbon FRP plate. Parameters involved in this experimental study were plate bond length and sheet web anchorage length. Test beams were strengthened with FRP plate on the soffit and anchored with FRP sheet on the web. In general, strengthened beams with no web anchorage were failed by concrete cover failure along the longitudinal reinforcement. On the other hand, strengthened beams with web anchorage were finally failed by delamination shear failure within concrete after breaking of CFRP sheet wrapping around web. The ultimate load and deflection of strengthened beams increased with an increased bond length of FRP plate. Also, the ultimate load and deflection increased with an increased anchorage length of FRP sheet. Particularly, the strengthened beams with web anchorage maintained high ultimate load resisting capacity until very large deflection. The shape of strain distribution of CFRP plate along beam was very similar to that of bending moment diagram. Therefore, an assumption of constant shear stress in shear span could be possible in the analysis of delamination shear stress of concrete. In the case of full bond length, the ultimate resisting shear stress provided by concrete and FRP sheet Increased with an increase of web anchorage length. In the resisting shear force, a portion of the shear force was provided by FRP anchorage sheet.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6D
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• pp.951-960
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• 2006

Structural pavement analysis considering lateral loads of moving vehicle was carried out in order to simulate passing vehicle loads under various interface conditions. To verify of existing multi-layer elastic analysis of layer interface effect parameters, this study compared outputs by using ABAQUS, a three dimensional finite element program and KENLAYER, multi-layer elastic analysis as vertical load was applied to the surface of asphalt pavements. Pavement performance depending on interface conditions was quantitatively evaluated and fundamental study of layer interface effect parameters was performed in this study. As results of the study, if only vertical loads of moving vehicle is applied, subdivision of either fully bonded or fully unbonded is enough to indicate interface effect parameters. On the other hand, when lateral loads are applied with vertical loads, pavement behavior and performance are greatly changed with respect to layer interface conditions. The thinner thickness of the asphalt layer is and the smaller elastic moduli of the asphalt layer is, the more pavement behavior is influenced by interface conditions. In addition, regression analysis equation analytically computing tensile strain which was considered thicknesses and elastic moduli of the asphalt layer and layer interface effect parameters at the bottom of the asphalt layer was presented using database from numerical analyses on national pavement model sections.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.287-296
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• 2019

In this study, the effect of ground boundary conditions on the evaluation of blast resistance performance of precast arch structures was evaluated by a numerical analysis method. Two types of boundary conditions, namely, fixed boundary conditions and a perfectly matched layer (PML) were applied to numerical models. Blast loads that were much higher than the design load of the target structure were applied to compare the effects of the boundary conditions. The distribution and path of the ground explosion pressure, structural displacement, fracture of concrete, stress of concrete, and reinforcing bars were compared according to the ground boundary condition settings. As a result, the reflecting pressure shock wave at the ground boundaries could be effectively eliminated using PML elements; furthermore, the displacement of the foundation was reduced. However, no distinct difference could be observed in the overall structural behavior including the fracture and stress of the concrete and rebar. Therefore, when blast simulations are performed in the design of protective structures, it is rational to apply the fixed boundary condition on the ground boundaries as conservative design results can be achieved with relatively short computation times.