• 대한토목학회논문집
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• 제28권4A호
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• pp.517-528
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• 2008

이 논문에서는 철근과 콘크리트 사이의 부착-슬립을 실제적으로 고려한 철근콘크리트 접합부의 이력 손상 모델을 제안하였다. 슬립을 가시화하기 위해 콘크리트와 철근의 변위장이 서로 다른 프레임 요소를 개발하였다. 파이버 단면 개념으로부터 콘크리트, 철근 그리고 부착에 대한 적합방정식을 정의하였다. 부분적인 제하 및 재재하 상태를 고려하기 위해 철근 이력곡선의 수정이 이루어졌다. 단조증가 상태의 국부적 부착응력-슬립 관계는 손상 계수에 따라 슬립이 역전될 때마다 갱신하였다. 구속된 콘크리트에 매입된 철근 시험체와 기초에 정착된 철근콘크리트 기둥 시험체, 그리고 보-기둥 부재의 수치해석을 통해 모델의 정확성을 검증하였고, 부착-슬립 효과를 고려함으로써 하중 이력에 따른 에너지 소산 정도를 평가할 수 있었다.

• Steel and Composite Structures
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• 제45권6호
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• pp.819-830
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• 2022

This paper presented an experimental study of the bond-slip behavior of reactive powder concrete (RPC)-filled square steel tube. A total of 18 short composite specimens were designed forstatic push-out test, and information on their failure patterns, load-slip behavior and bond strength was presented. The effects of width-to-thickness ratio, height-to-width ratio and the compressive strength of RPC on the bond behavior were discussed. The experimental results show that:(1) the push-out specimens remain intact and no visible local buckling appears on the steel tube, and the interfacial scratches are even more pronounced at the internal steel tube of loading end; (2) the bond load-slip curves with different width-to-thickness ratios can be divided into two types, and the main difference is whether the curves have a drop in load with increasing slip; (3) the bond strength decreases with the increase of the width-to-thickness ratio and height-width ratio, while the influence of RPC strength is not consistent; (4) the slippage has no definite correlation with bond strength and the influence of designed parameters on slippage is not evident. On the basis of the above analysis, the expressions of interface friction stress and mechanical interaction stress are determined by neglecting chemical adhesive force, and the calculation model of bond strength for RPC filled in square steel tube specimens is proposed. The theoretical results agree well with the experimental data.

• Computers and Concrete
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• 제23권3호
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• pp.155-160
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• 2019

The use of recycled aggregate concrete for the purpose of environmental and resource conservation has gained increasing interest in construction engineering. Nevertheless, few studies have reported on the bonding performance of the bars in recycled aggregate concrete after exposed to high temperatures. In this paper, 72 pull-out specimens and 36 cubic specimens with different recycled coarse aggregate content (i.e., 0%, 50%,100%) were cast to evaluate the bond behavior between recycled aggregate concrete and steel bar after various temperatures ($20^{\circ}C$, $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$). The results show that the recycled aggregate concrete pull-out specimens exhibited similar bond stress-slip curves at both ambient and high temperature. The bond strength declined gradually with the increase of the temperature. On the basis of a regression analysis of the experimental data, a revised bond strength mode and peak slip ratios relationship model were proposed to predict the post-heating bond-slip behavior between recycled aggregate concrete and steel bar.

• 한국전산구조공학회논문집
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• 제23권1호
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• pp.95-110
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• 2010

본 논문에서는 합성보의 부착슬립 효과를 고려할 수 있는 유한요소 수치모델을 제안하고자 한다. 전단연결재가 설치된 슬래브와 거더 경계에서 선형 전단력-슬립 관계를 가정하여, 부착슬립 거동을 해석할 수 있는 수치모델이 구현되었다. 본 수치모델을 통하여 축 방향의 자유도를 부가하지 않고 2절점의 보 요소를 적용하여 합성보 경계에서의 슬립 거동을 고려하는 것이 가능하다. 선형 부분전단 연결이론을 토대로 한 슬립 거동의 지배방정식은 슬래브와 거더 경계에서 힘의 평형상태와 단면 내에서 상수로 가정된 곡률을 바탕으로 결정된다. 또한, 지배방정식 구성에 있어서 요소 양 절점에서의 휨 모멘트 값을 필요로 하기 때문에 유한요소 해석으로 도출되는 상수 모멘트를 요소 내에서 선형으로 분포시켰다. 제안된 수치모델을 적용한 해석결과를 기존 연구의 수치해석 결과 및 실험결과와 비교하였으며, 하중-처짐 곡선의 비교를 통하여 본 모델의 성능을 검증하였다.

• Earthquakes and Structures
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• 제14권3호
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• pp.187-201
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• 2018

The paper describes a modified cyclic bar model including bond-slip phenomena between steel reinforcing bars and surrounding concrete. The model is focused on plain bar and is useful, for its simplicity, for the seismic analyses of RC structures with plain bars and insufficient constructive details, such as in the case of '60s -'70s Mediterranean buildings. The model is based on an imposed exponential displacements field along the bar including both steel deformation and slip; through the adoption of equilibrium and compatibility equations a stress-slip law can be deducted and simply applied, with opportune operations, to RC numerical models. This study aims to update and complete the original monotonic model published by the authors, solving some numerical inconsistencies and, mostly, introducing the cyclic formulation. The first aim is achieved replacing the imposed linear displacement field along the bar with an exponential too, while the cyclic behaviour is described through a formulation based on the results of parametric analyses concerning a large range of steel and concrete properties and geometric configurations. Validations of the proposed model with experimental results available in the current literature confirm its accuracy and the reduced computational burden, highlighting its suitability in performing nonlinear analyses of RC structures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.917-922
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• 2002

This paper deals with the estimation of the maximum crack widths considering bond-slip relationships based on experimental data that were tensed by axial force. It is certificated that the concrete stress condition clearly affects the bond-slip relationship. The proposed method utilizes the conventional crack and bond-slip theories as well as the characteristics of deformed reinforcement and size effects. An analytical equation for the estimation of the maximum flexural crack width is formulated as a function of minimum crack length and the coefficient of bond stress effect. The validity, accuracy and efficiency of the proposed method are established by comparing the analytical results with the experimental data and the major specifications (e.g., ACI, CEB-FIP Model code, Turocode 2, JSCE, etc.). The analytical results presented in this paper indicate that the proposed method can be effectively estimated the maximum flexural crack width of reinforced concrete.

• Computers and Concrete
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• 제16권3호
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• pp.449-466
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• 2015

This paper aims to study the local bond stress-slip behavior of reinforcing bars embedded in lightweight aggregate concrete (LWAC). The experimental variables of the local bond stress-slip tests include concrete strength (20, 40 and 60 MPa), deformed steel bar size (#4, #6 and #8) and coarse aggregate (normal weight aggregate, reservoir sludge lightweight aggregate and waterworks sludge lightweight aggregate). The test results show that the ultimate bond strength increased with the increase of concrete compressive strength. Moreover, the larger the rib height to the diameter ratio ($h/d_b$) of the deformed steel bars is, the greater the ultimate bond stress is. In addition, the suggestion value of the CEB-FIP Model Code to the LWAC specimen's ultimate bond stress is more conservative than that of the normal weight concrete.

• Computers and Concrete
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• 제19권4호
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• pp.375-385
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• 2017

In the present paper experimental and numerical analysis of hook-ended steel fiber reinforced concrete is carried out. The experimental tests are performed on notched beams loaded in 3-point bending using fiber volume fractions up to 1.5%. The numerical analysis of fiber reinforced concrete beams is performed at meso scale. The concrete is discretized with 3D solid finite elements and microplane model is used as a constitutive law. The fibers are modelled by randomly generated 1D truss finite elements, which are connected with concrete matrix by discrete bond-slip relationship. It is demonstrated that the presented approach, which is based on the modelling of concrete matrix using microplane model, able to realistically replicate experimental results. In all investigated cases failure is due to the pull-out of fibers. It is shown that with increase of volume content of fibers the effective bond strength and slip capacity of fibers decreases.

• Computers and Concrete
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• 제19권6호
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• pp.625-630
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• 2017

In this paper, 54 pull-out specimens and 36 cubic specimens with different replacement ratios of fly ash in the concrete (i.e., 0%, 20%, 30%, 40%, 50%, 60%) were fabricated to evaluate the bond at the interface between fly ash concrete and steel rebar. The results showed that the general shape of the bond-slip curve between fly ash concrete and steel rebar was similar to that for the normal concrete and steel rebar. The bond strength between fly ash concrete and the steel rebar was closer to each other at the same rebar diameter, irrespective of the fly ash replacement percentage. On the basis of a regression analysis of the experimental data, a revised bond strength mode and bond-slip relationship model were proposed to predict the bond-slip behaviour of high volume fly ash concrete and steel rebar.

• 한국산학기술학회논문지
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• 제16권3호
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• pp.2279-2286
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• 2015

GFRP 판을 영구 거푸집 및 주요 인장 보강재로 활용한 GFRP-콘크리트 하이브리드 구조의 활용에 대해 최근 활발하게 연구가 이루어지고 있다. GFRP 판과 콘크리트 하이브리드 구조의 거동을 이해하기 위해서는 GFRP 판과 현장타설 고강도콘크리트 사이의 정량적인 국부 부착슬립모델이 필요하다. 본 연구에서는 이러한 하이브리드 구조에 간단하게 적용할 수 있는 2중 직선 단순 부착슬립관계를 제안하고자 한다. 본 연구에서 제안된 단순 부착슬립관계의 최대 평균 부착응력은 3.29MPa이며, 초기 기울기는 35.66MPa/mm, 총 슬립은 0.23mm이고 계면 파괴에너지는 0.37kN/m로 나타났다.