• 콘크리트학회논문집
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• 제29권1호
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• pp.11-21
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• 2017

본 연구는 OPC-GGBFS 페이스트 시험체에 균열을 발생시키지 않은 시험체와 균열을 발생시킨 시험체의 자기치유 효과에 대한 실험결과이다. 균열이 발생된 시험체의 자기치유는 균열면의 미수화 입자들의 재수화로 인한 균열면 닫힘 현상이다. OPC 페이스트에 GGBFS를 0%, 10%, 20% 그리고 30% 치환하고 물-결합재 비는 0.5로 일정하게 하였다. OPC-GGBFS 시험체를 담수(tap-water)와 해수(sea-water)에 침지하였다. 담수와 해수의 온도는 $5^{\circ}C$, $15^{\circ}C$ 그리고 $25^{\circ}C$이다. 균열을 발생시킨 시험체는 균열발생 후 60까지 침지하였다. 실험결과를 바탕으로 자기치유 효과(self-effect)와 재령효과(age-effect) 사이의 관계를 계산하였다. 자기치유 효과는 균열발생 전후의 초음파속도(UPV) 측정을 통해 이루어졌다. GGBFS 치환율이 증가하면 UPV 증가율이 증가하였다. 더구나, 침지한 담수의 온도가 증가할수록 자기치유 효과도 향상되었다. 그러나 해수에 침지한 시험체는 온도와의 관계가 명확하지 않았다. 담수와 해수에 침지한 OPC-GGBFS 시험체의 가장 높은 자기치유 효과는 침지 30일 동안 발생하였다. 침지 30일까지는 자기치유효과가 높았다. 30일 이후에는 자기치유 효과와 재령 효과가 모두 크게 감소하였다. SEM/EDS 분석을 통해 담수에 침지한 시험체의 균열에는 aragonite가, 해수에 침지한 시험체의 균열부에는 brucite가 생성된 것을 확인하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.433-439
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• 2005

This paper describes a reinforced concrete crack model, which utilizes a strain decomposition technique. The strain decomposition technique enables the explicit inclusion of physical behavior across the cracked concrete surface such as aggregate interlock and dowel action rather than intuitively defining the shear retention factor. The proposed concrete crack model is integrated into the commercial finite element software ABAQUS shell elements through a user-supplied material subroutine. The FE results have been compared to experimental results reported by other researchers. The proposed bridge FE model is capable of predicting the initial cracking load level, the ultimate load capacity, and the crack pattern with good accuracy.

• International Journal of Concrete Structures and Materials
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• 제9권2호
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• pp.255-266
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• 2015

A strut-and-tie based method intended for determining the load-carrying capacity of reinforced concrete (RC) corbels is presented in this paper. In addition to the normal strut-and-tie force equilibrium requirements, the proposed model is based on secant stiffness formulation, incorporating strain compatibility and constitutive laws of cracked RC. The proposed method evaluates the load-carrying capacity as limited by the failure modes associated with nodal crushing, yielding of the longitudinal principal reinforcement, as well as crushing or splitting of the diagonal strut. Load-carrying capacity predictions obtained from the proposed analysis method are in a better agreement with corbel test results of a comprehensive database, comprising 455 test results, compiled from the available literature, than other existing models for corbels. This method is illustrated to provide more accurate estimates of behaviour and capacity than the shear-friction based approach implemented by the ACI 318-11, the strut-and-tie provisions in different codes (American, Australian, Canadian, Eurocode and New Zealand).

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.225-228
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• 2005

In this paper, an example of nonlinear analysis for partial prestressing design is presented. For partial prestressing design, the stress redistribution, after concrete cracking has occurred, should be accurately investigated by nonlinear analysis tools. Direct and iterative methods of nonlinear analyses were adopted for the tender design of the Incheon Bridge viaducts. Stress variations in the prestressing tendons and reinforcing bars were investigated and presented in this paper for both the in-service condition and during construction.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.367-370
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• 2003

This study was carried out to suggest the effective reinforcing method which can evaluate the tensile capacity of cast-in-place anchor with cracks. Currently, cast-in-place anchor is used widely for the fastening of equipment in Korean NPPs. 26 test specimens with a single anchor under 4 cracked conditions are prepared using plain concrete. The distance between crack and anchor and reinforcing materials were selected as the main test variable. The tensile force was applied using a actuator with a capacity of 100 tonf using a displacement control method of 0.5 mm/min velocity. Test results from this result show the combination of carbon plate and epoxy will be more available for repair and reinforcement of equipment foundation system in NPPs. Further experimental work is indeed involving the epoxy injection effect and adjustment of reinforcing location of carbon sheet.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.662-667
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• 2001

In this paper, damping behavior of steel fiber reinforced concrete(SFRC) beams by experimental and numerical method is discussed. Because of its improved ability to dissipate energy, SFRC has a better damping behavior than that of reinforced concrete(RC). Damping behavior is influenced by longitudinal reinforcement ratio, volume and type of steel fiber, strength of concrete and the stress level. Damping in the SFRC beams has been evaluated from dynamic experimental test data at various levels of cracked states in the beams. A FEM program(TICAL) has been developed based on the relationships between curvature and damping. It is observed for SFRC beams with 0.44% of tensile reinforcement steel that approximate 5% to 35% was relatively increased in the damping ratio generally depending on the load level.

• 한국철도학회논문집
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• 제8권2호
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• pp.122-127
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• 2005

In this paper, damping behavior of steel fiber reinforced concrete(SFRC) beams by experimental and numerical method is discussed. Because of its improved ability to dissipate energy, SFRC has a better damping behavior than that of reinforced concrete(RC). Damping behavior is influenced by longitudinal reinforcement ratio, volume md type of steel fiber, strength of concrete and the stress level. Damping in the SFRC beams has been evaluated from dynamic experimental test data at various levels of cracked states in the beams. A FEM program(TICAL) has been developed based on the relationships between curvature and damping. It is observed far SFRC beams with 0.44$\%$ of tensile reinforcement steel that approximate 5$\%$ to 35$\%$ was relatively increased in the damping ratio generally depending on the load level.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.751-756
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• 2000

The structural behavior of reinforced concrete slabs strengthened by glass fiber reinforced plastic-panels experimentally investigated. The experimental variables are strengthening length, strengthening width, and pre-crack existence. The pre-cracked slabs are initially loaded to 70 percent of ultimate flexural capacity and subsequently repaired with GFRP-Panels bonded to the tension face of the slabs. Five one-way slabs were tested to failure. The main failure mode of strengthened slabs is separation failure by crack propagation from load point section to end of plate. The behavior of strengthened slabs is represented by a maximum load, load-deflection curves an load-strain curves.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.397-402
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• 2003

This paper presents strut-and-tie models for predicting shear strength of RC interior beam-column joints considering the plastic hinge rotation of adjacent beams. On seismic design of frame system, it is controlled beams to occur plastic hinges and to be ductile so as to dissipate earthquake energy efficiently. The plastic hinge deformation of beams is used as analysis parameter in terms of strain of beam tensile bars at column face. The shear strengths of beam-column joints are evaluated by combining direct strut mechanism with truss mechanism. It is assumed that the max force transferred by direct strut mechanism is based on the strength of cracked concrete element, and that by truss mechanism is based on bond capacity.

• Steel and Composite Structures
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• 제1권2호
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• pp.245-268
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• 2001

The analysis of steel-concrete composite joints presents some particular aspects that increase their complexity when compared to bare steel joints. In particular, the influence of slab reinforcement and column concrete encasement clearly change the moment-rotation response of the joint. Starting from an energy approach developed in the context of steel joints, an extension to composite joints is presented in this paper that is able to provide closed-form analytical solutions. In addition, the possibility of tri-linear or non-linear component behaviour is also incorporated in the model, enabling adequate treatment of the influence of cracked concrete in tension and the softening response of the column web in compression. This methodology is validated through comparison with experimental tests carried out at the University of Coimbra.