• Computers and Concrete
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• v.7 no.6
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• pp.497-510
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• 2010

For better estimation of elastic property of concrete composites, the effect of Interfacial Transition Zone (ITZ) has been found to be significant. Numerical concrete composites models have been introduced using Finite Element Method (FEM), where ITZ is modeled as a thin shell surrounding aggregate. Therefore, difficulties arise from the mesh generation. In this study, a numerical concrete composites model in 3D based on FEM and random unit cell method is proposed to calculate elastic modulus of concrete composites with ITZ. The validity of the model has been verified by comparing the calculated elastic modulus with those obtained from other analytical and numerical models.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.167-170
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• 2005

This paper summarizes the results of a series of numerical evaluations (Lee et al., 2004, 2005) on the performance of pre-cracked reinforced concrete (RC) beams coated with polymeric composites. It was intended to numerically show the superior characteristics of the polymeric composites for enhancing the strength and ductility of existing concrete structures. Further, the predicted load-carrying and energy absorbing capacities of the beams were compared with previous experiments to verify the predictive capability of implemented computational model.

• Advances in concrete construction
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• v.16 no.2
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• pp.107-117
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• 2023

Textile-reinforced concrete composite (TRC) is a new alternative material that can satisfy sustainable development needs in the civil engineering field. Its mechanical behaviour and properties have been identified from the experimental works. However, it is necessary for a numerical approach to consider the effect of the parameters on TRC's behaviour with lower analysis duration and cost related to the experiment. This paper presents obtained results of the numerical modelling for TRC composite using the cracking model for the cementitious matrix in TRC. As a result, the TRC composite exhibited a strain-hardening behaviour with the cracking phase characterized by the drops in tensile stress on the stress-strain curve. This model also showed the failure mode by multi-cracking on the TRC specimen surface. Furthermore, the parametric studies showed the effect of several parameters on the TRC tensile behaviour, as the reinforcement ratio, the length and position of the deformation measurement zone, and elevated temperatures. These numerical results were compared with the experiment and showed a remarkable agreement for all cases of this study.

• Computers and Concrete
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• v.10 no.2
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• pp.135-147
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• 2012

At mesoscale, concrete is considered as a three-phase composite material consisting of the aggregate particles, the cement matrix and the interfacial transition zone (ITZ). The reconstruction of the internal structures for concrete composites requires the identification of the boundary of the aggregate particles and the cement matrix using digital imaging technology followed by post-processing through MATLAB. A parameter study covers the subsection transformation, median filter, and open and close operation of the digital image sample to obtain the optimal parameter for performing the image processing technology. The subsection transformation is performed using a grey histogram of the digital image samples with a threshold value of [120, 210] followed by median filtering with a $16{\times}16$ square module based on the dimensions of the aggregate particles and their internal impurity. We then select a "disk" tectonic structure with a specific radius, which performs open and close operations on the images. The edges of the aggregate particles (similar to the original digital images) are obtained using the canny edge detection method. The finite element model at mesoscale can be established using the proposed image processing technology. The location of the crack determined through the numerical method is identical to the experimental result, and the load-displacement curve determined through the numerical method is in close agreement with the experimental results. Comparisons of the numerical and experimental results show that the proposed image processing technology is highly effective in reconstructing the internal structures of concrete composites.

• Computers and Concrete
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• v.4 no.4
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• pp.273-284
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• 2007

The paper considers a theoretical model for the study of the process of transfer of sulfate ions in saturated porous media - mineral composites. In its turn, the model treats diffusion of sulfate ions into cement based composites, accounting for simultaneous effects such as filling of micro-capillaries with ions and chemical products and liquid push out of them. The proposed numerical algorithm enables one to account for those simultaneous effects, as well as to model the diffusive behavior of separate sections of the considered volume, such as inert fillers. The cases studied illustrate the capabilities of the proposed model and those of the algorithm developed to study diffusion, considering the specimen complex configuration. Computations show that the theoretical assumptions enable one to qualitatively estimate the experimental evidence and the capabilities of the studied composite. The results found can be used to both assess the sulfate corrosion in saturated systems and predict and estimate damage of structures built of cement-based mineral composites.

• Structural Engineering and Mechanics
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• v.30 no.2
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• pp.147-164
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• 2008

Recently, many researches have been done to examine the behavior of fiber reinforced concrete (FRC) subjected to the static loading. However, a few studies have been devoted to cyclic behaviors of FRC. A main objective of this paper is to investigate the cyclic behavior of FRC through theoretical method. A new cyclic bridging model was proposed for the analysis of fiber reinforced cementitious composites under cyclic loading. In the model, non-uniform degradation of interfacial bonding under cyclic tension was considered. Fatigue test results for FRC were numerically simulated using proposed models and the proposed model is achieving better agreement than the previous model. Consequently, the model can establish a basis for analyzing cyclic behavior of fiber reinforced composites.

• Structural Engineering and Mechanics
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• v.8 no.3
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• pp.273-283
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• 1999

Two physical experiments are performed to verify the effectiveness of beam-particle model for simulating the progressive failure of particulate composites such as sandstone and concrete. In the numerical model, the material is schematized at the meso-level as an assembly of discrete, interacting particles which are linked through a network of brittle breaking beams. The uniaxial compressive tests of cubic and parallelepipedal specimens made of carbon steel rod assembly which are glued together by a mixture are represented. The crack patterns and load-displacement response observed in the experiments are in good agreement with the numerical results. In the application respect of beam-particle model to the particulate composites, the influence of defects, particle arrangement and boundary conditions on crack propagation is approached, and the correlation existing between the cracking evolution and the level of loads imposed on the specimen is characterized by fractal dimensions.

• Computers and Concrete
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• v.12 no.4
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• pp.565-583
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• 2013

Existing numerical models for strain-hardening cement-based composites (SHCC) are short of providing sufficiently accurate solutions to the failure patterns of coupling beams of different designs. The objective of this study is to develop an effective model that is capable of simulating the nonlinear behavior of SHCC coupling beams subjected to cyclic loading. The beam model proposed in this study is a macro-scale plane stress model. The effects of cracks on the macro-scale behavior of SHCC coupling beams are smeared in an anisotropic model. In particular, the influence of the defined crack orientations on the simulation accuracy is explored. Extensive experimental data from coupling beams with different failure patterns are employed to evaluate the validity of the proposed SHCC coupling beam models. The results show that the use of the suggested shear stiffness retention factor for damaged SHCC coupling beams is able to effectively enhance the simulation accuracy, especially for shear-critical SHCC coupling beams. In addition, the definition of crack orientation for damaged coupling beams is found to be a critical factor influencing the simulation accuracy.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.543-548
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• 2003

In this study, a numerical model is developed using axial deformation link elements that can effectively predict the failure behavior of RC type structures. Using this mod 1, numerical analysis was performed to investigate the strengthening effect and failure behavior of structures repaired with a new material. High-Performance Cementitious Composites, which is characterized by its ductility with 5% strain-capacity is used as a repair material. To investigate the validity of developed numerical model, simulations of direct tension specimen and flexural specimen are performed and the results are compared with published ones. The similar analysis is performed for RC beam. Through this study, it is seen that predicted response has a good agreement with the experimental results. Using this verified numerical model, the strengthening effect of repaired with HPCC structure is analyzed through load-displacement curve and failure modes. Also, the same numerical analysis is performed in RC beam repaired with HPCC. The effect of HPCC ductility is estimated for the overall behavior of structures. Based on the results, the fundamental data are suggested for repaired structures with HPCC.

• Computers and Concrete
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• v.9 no.3
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• pp.171-178
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• 2012

This paper presents numerical studies of stiff fiber pullout behaviors of fiber reinforced cementitious composites based on a progressive damage model. The ongoing debonding process is simulated. Interfacial stress distribution for different load levels is analyzed. A parametric study, including bond strength and the homogeneity index on the pullout behaviors is carried out. The numerical results indicate that the bond stress decreases gradually from loaded end to embedded end along fiber-cement interface. The debonding initially starts from loaded end and propagates to embedded end as load increasing. The embedded length and bond strength affect the load-loaded end displacement curves significantly. The numerical results have a general agreement with the experimental investigation.