• International Journal of Concrete Structures and Materials
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• 제18권2E호
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• pp.125-132
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• 2006

Waste glass has been increasingly used in industrial applications. One shortcoming in the utilization of waste glass for concrete production is that it can cause the concrete to be weakened and cracked due to its expansion by alkali-silica reaction(ASR). This study analyzed the ASR expansion and strength properties of concrete in terms of waste glass color(amber and emerald-green), and industrial by-products(ground granulated blast-furnace slag, fly ash). Specifically, the role of industrial by-products content in reducing the ASR expansion caused by waste glass was analyzed in detail. In addition, the feasibility of using ground glass for its pozzolanic property was also analyzed. The research result revealed that the pessimum size for waste glass was $2.5{\sim}1.2mm$ regardless of the color of waste glass. Moreover, it was found that the smaller the waste glass is than the size of $2.5{\sim}1.2mm$, the less expansion of ASR was. Additionally, the use of waste glass in combination with industrial by-products had an effect of reducing the expansion and strength loss caused by ASR between the alkali in the cement paste and the silica in the waste glass. Finally, ground glass less than 0.075 mm was deemed to be applicable as a pozzolanic material.

• Structural Engineering and Mechanics
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• 제12권1호
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• pp.1-16
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• 2001

A reliable and accurate method has been developed to predict the flexural deformation response of structural concrete members subject to service load. The method that has been developed relates the extent of concrete cracking, measured as a function of the magnitude of applied moment in a member, to the reduction in the effective moment of inertia of cracked reinforced concrete members under service load conditions. The ratio of the area of the moment diagram where the moment exceeds the cracking moment, to the total area of the moment diagram for any loading, provides the basis for the calculation of the effective moment of inertia. This ratio also represents mathematically a probability of crack occurrence. Verification of this method for the determination of the effective moment of inertia has been achieved from an experimental test program, and has included beam tests with different loading configurations, and shear wall tests subjected to a range of vertical and lateral load levels. Further verification of this method has been made with reference to the experimental investigation of other recently published work.

• Computers and Concrete
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• 제8권3호
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• pp.343-355
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• 2011

This paper presented the model to predict the chloride diffusion coefficient in tension zone of plain concrete under flexural cyclic load. The fictitious crack based analytical model was used together with the stress degradation law in cracked zone to predict crack growth of plain concrete beams under flexural cyclic load. Then, under cyclic load, the chloride diffusion, in the steady state and one dimensional regime, through the tension zone of the plain concrete beam, in which microcracks were formed by a large number of cycles, was simulated with assumptions of continuously straight crack and uniform-size crack. The numerical analysis in terms of the chloride diffusion coefficient, $D_{tot}$, normalized $D_{tot}$, crack width and crack length was issued as a function of the load cycle, N, and load level, SR. The nonlinear model as regarding with the chloride diffusion coefficient in tension zone and the load level was proposed. According to this model, the chloride diffusion increases with increasing load level. The predictions using model fit well with experimental data when we adopted suitable crack density and tortuosity parameter.

• Structural Engineering and Mechanics
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• 제54권2호
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• pp.319-336
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• 2015

Life cycle performance of corrosion affected RC structures is an important and challenging issue for effective infrastructure management. The accurate condition assessment of corroded RC structures mainly depends on the effective evaluation of deterioration occurring in the structures. Structural performance deterioration caused by reinforcement corrosion is a complex phenomenon which is generally uncertain and non-decreasing. Therefore, a stochastic modelling such as the gamma process can be an effective tool to consider the temporal uncertainty associated with performance deterioration. This paper presents a time-dependent reliability analysis of corrosion affected RC structures associated bond strength degradation. Initially, an analytical model to evaluate cracking in the concrete cover and the associated loss of bond between the corroded steel and the surrounding cracked concrete is developed. The analytical results of cover surface cracking and bond strength deterioration are examined by experimental data available. Then the verified analytical results are used for the stochastic deterioration modelling, presented here as gamma process. The application of the proposed approach is illustrated with a numerical example. The results from the illustrative example show that the proposed approach is capable of assessing performance of the bond strength of concrete structures affected by reinforcement corrosion during their lifecycle.

• 한국철도학회논문집
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• 제13권4호
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• pp.431-439
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• 2010

강섬유콘크리트는 터널의 숏크리트와 산업슬래브포장과 같은 적용 분야에서는 벌써 주목할 정도로 성공적인 반면에 일반적인 건설실무에서는 적용가능성이 주로 경제적인 이유로 해서 지금 까지는 부분적으로 제한되었다. 동적하중을 받는 특수한 분야 예를 들면 충격하중, 지진하중 및 철도의 피로하중등과 같은 동적하중이 작용하는 구조물에 대해서는 흥미로운 가능성을 열어 놓고 있다. 따라서 연구에서는 저자 연구소에서 수행한 다양한 동하중을 받는 구조물에 강섬유콘크리트를 적용할 수 있도록 강섬유콘크리트의 에너지 감쇠, 충격특성 및 피로거동 등을 실험적으로 수행한 연구결과로 보여준다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 가을 학술발표회 논문집
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• pp.185-193
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• 1995

The softening behaviors of concrete have been the object of numerous experimental and numerical studies, because the load carrying capacity of cracked concrete structure is not zero. Numerical studies are devoted to the investigation of three-dimensional softening behaviors of concrete on the basis of a viscoplastic theory, which may be able to represent the effects of plasticity and also of rheology. In order to properly describe material behaviors corresponding to different stress levels, two surfaces in stress space are adopted; one is a yield surface, and the other is a failure or bounding surface. When a stress path reaches the failure surface, it is considered that the softening behaviors are initiated as micro-cracks coalesce and are simulated by assuming that the actual strain increments in the post-peak region are less than the equivalent viscoplastic strain increment. The experimental studies and the finite element analyses have been carried out under the displacement control. Numerically simulated results indicate that the model is able to predict the essential characteristics of concrete behaviors such as the non-linearity, stiffness degradation, different behaviors in tension and compression, and specially dilatation under uniaxial compression.

• Computers and Concrete
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• 제15권3호
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• pp.411-436
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• 2015

In this work, a comprehensive approach to model the structural behaviour of Reinforced Concrete (RC) beams subjected to reinforcement corrosion is proposed. The coupled environmental - mechanical damage model developed by some of the authors is enhanced for considering the main effects of corrosion on concrete, on composite interaction between reinforcement bars and concrete and on steel reinforcement. This approach is adopted for reproducing a set of experimental tests on RC beams with different corrosion degrees. After the simulation of the sound beams, the main parameters involved in the relationships characterizing the effects of corrosion are calibrated and tested, referring to one degraded beam. Then, in order to validate the proposed approach and to assess its ability to predict the structural response of deteriorated elements, several corroded beams are analyzed. The numerical results show a good agreement with the experimental ones: in particular, the proposed model properly predicts the structural response in terms of both failure mode and load-deflection curves, with increasing corrosion level.

• Computers and Concrete
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• 제15권1호
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• pp.37-54
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• 2015

In general, cracks significantly deteriorate the in-situ performance of concrete members and structures, especially in urban metro tunnels that have been embedded in saturated soft soils. The microcapsule self-healing method is a newly developed healing method for repairing cracked concrete. To investigate the optimal microcapsule parameters that will have the best healing effect in concrete, a 3D analytical probability healing model is proposed; it is based on the microcapsule self-healing method's healing mechanism, and its purpose is to predict the healing efficiency and healing probability of given cracks. The proposed model comprehensively considers the radius and the volume fraction of microcapsules, the expected healing efficiency, the parameters of cracks, the broken ratio and the healing probability. Furthermore, a simplified probability healing model is proposed to facilitate the calculation. Then, a Monte Carlo test is conducted to verify the proposed 3D analytical probability healing model. Finally, the influences of microcapsules' parameters on the healing efficiency and the healing probability of the microcapsule self-healing method are examined in light of the proposed probability model.

• Computers and Concrete
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• 제13권4호
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• pp.569-585
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• 2014

In this paper, a four-layer road structure consisting of an edge transverse crack is simulated using three-dimensional finite element method in order to capture the influence of a single-axle wheel load on the crack propagation through the asphalt concrete layer. Different positions of the vehicular load relative to the cracked area are considered in the analyses. Linear elastic fracture mechanics (LEFM) is used for investigating the effect of the traffic load on the behavior of a crack propagating within the asphalt concrete. The results obtained show that the crack front experiences all three modes of deformation i.e., mode I, mode II and mode III, and the corresponding stress intensity factors are highly affected by the crack geometry and the vehicle position. The results also show that for many loading situations, the contribution of shear deformation (due to mode II and mode III loading) is considerable.

• Computers and Concrete
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• 제11권4호
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• pp.305-316
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• 2013

This paper aims to study the effect of measurement methods and cracking on chloride transport of concrete materials. Three kinds of measurement methods were carried out, including immersion test, rapid migration test and steady-state migration test. All of these measurements of chloride transport show that chloride ion diffusion coefficient decreased with the reduction of water to cement ratio. Results of the immersion test were less than that of rapid migration test and steady-state migration test. For the specimen of lower water to cement ratio, the external electrical field has little effect on chloride binding relatively. Compared with the results obtained by these different measurement methods, the lower water to cement ratio may cause smaller differences among these different methods. The external voltage can reduce chloride binding of concrete, and the higher electrical field made a strong impact on the chloride binding. Considering the effect of high voltage on the specimen, results indicate that results based on the steady-state migration test should be more reasonable. For cracked concrete, cracking can accelerate the chloride ion diffusion.