• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.1
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• pp.103-111
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• 2020

Pulling-type cutting devices, which use a diamond wire saw, have been used generally for cutting concrete structures. In this study, a pushing-type cutting device with a collection cover was developed by overcoming the disadvantages of pulling-type devices. In this device, dry or liquid methods can be selected to cool frictional heat. Operation and leakage tests of the dust generated during the dismantling of a concrete structure were carried out, confirming the suitable operation of the fabricated cutting device; the leakage rate was approximately 1.7%. For a conservative evaluation, the internal dose of workers was estimated in dismantling the core center part of biological shield concrete with a specific activity of 99.5 Bq·g^-1. The committed effective dose per worker was 0.25 mSv. The developed cutting device contributed to reducing radioactive concrete waste and minimizing worker exposure due to its easy installation. Therefore, it can be utilized as a cutting apparatus for dismantling not only reinforced concrete structures but also radioactive biological shield concrete in nuclear power plant decommissioning efforts.

• Nuclear Engineering and Technology
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• v.44 no.3
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• pp.331-342
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• 2012

Since the opening of the Shin-Kori #1,2 in 2005, fly ash mixed concrete has been used for NPP concrete structures under construction in Korea with the aim of preventing aging and improving durability. In this paper, the quality suitability of fly ash manufactured in Korea is assessed and the basic physical properties of fly ash mixed concrete and its durability against primary causes of aging are verified through experimental methods. Because of the internal structure filling effect from the pozzolanic reaction of fly ash and the resulting improvements in mechanical performance in such areas as strength and salt damage resistance, the durability of fly ash mixed concrete is shown to be superior. It is judged that this result can be applied in measures not only for improving the safety of NPP structures in operation in Korea but also for implementing effective structure life management should extending the life of structures be needed in the future.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.204-206
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• 2008

In this paper, we proposed the recognition method that automatically extracts cracks from a surface image acquired by a digital camera and recognizes the directions (horizontal, vertical, -45 degree, and 45 degree) of cracks using the fuzzy single layer perceptron. We compensate an effect of light on a concrete surface image by applying the closing operation, which is one of the morphological techniques, extract the edges of cracks by Sobel masking, and binarize the image by applying the iterated binarization technique. Two times of noise reduction are applied to the binary image for effective noise elimination. After the specific regions of cracks are automatically extracted from the preprocessed image by applying Glassfire labeling algorithm to the extracted crack image, the cracks of the specific region are enlarged or reduced to $30{\times}30$ pixels and then used as input patterns to the fuzzy single layer perceptron. The experiments using concrete crack images showed that the cracks in the concrete crack images were effectively extracted and the fuzzy single layer perceptron was effective in the recognition of the extracted cracks directions.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.351-356
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• 1997

With the aid of advanced structural engineering, the construction of infrastructures has been recently accelerating to keep up with rapid economic growth. Construction activities and operation of transportation facilities cause civil petitions associated with vibration-induced damages or nuisances. As part of the decrease of vibration induced damage, the objective of this study is to develop vibration-controlled concrete with vibration-reduced materials, which can be recycled from obsolete materials, such as aged tires, plastics and etc. Appropriate mix proportion has been used for making 10 reinforced concrete panels with vibration-reduced materials, which have been tested to investigate on vibration reduction capability, based on the time and frequency domain analysis, and vibration velocity level analysis. Vibration-reduced mixtures are latex, styrofoam, rubber powder and plastic resin, which have been determined to by reduce vibration.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.521-526
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• 1997

The Spin Tester(High Speed Balancing and Overspeed Test Facility), which is designed for the quality control of turbine, generator, and rotors was supposed to be constructed with the use of Steel Fiber Reinforced Concrete(SERC) for reducing the risk of accident while operation. However, it was very existence of fiber concrete due to there are two major concern in the SFRC work: one is existence of fiber ball due to inhomogeneous mixing, the other is the segregation of the concrete materials. To avoid these possible problems, the S/a was controlled about 55% to reduce the segregation and the high range AE water reducing agent was used to maintain the slump over the value of 18cm. With these careful consideratons, the SFRC work was done successfully by only using regular equipments like pump car and vibrator.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.500-507
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• 1997

Recently, the construction of infrastructures has been booming and accelerating to keep up with rapid economic growth. Construction activities and operation of transportation facilities cause unfavorable effects such as civil petitions associated with vibration-induced damages or nuisances. The objective of this study is to develop vibration-controlled concrete using various vibration-controlling materials , and also to investigate dynamic properties of concrete beam depending on damage level. Vibration-controlled mixtures are latex, rubber powder and plastic resin, which have been determines to by and large reduce vibration. KS F2437 has been used to figure out 1st natural frequency and dynamic flexural rigidity. Dynamic damping rations have been, computed by adopting the polynomial curvefitting method on the frequency spectrum curve, of which results have been compared and analyzed hereon

• Smart Structures and Systems
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• v.29 no.3
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• pp.421-431
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• 2022

Concrete slab cracks monitoring of modern high-speed railway is important for safety and reliability of train operation, to prevent catastrophic failure, and to reduce maintenance costs. This paper proposes a curvature filtering improved crack detection method in concrete slabs of high-speed railway via graph-based anomalies calculation. Firstly, large curvature information contained in the images is extracted for the crack identification based on an improved curvature filtering method. Secondly, a graph-based model is developed for the image sub-blocks anomalies calculation where the baseline of the sub-blocks is acquired by crack-free samples. Once the anomaly is large than the acquired baseline, the sub-block is considered as crack-contained block. The experimental results indicate that the proposed method performs better than convolutional neural network method even under different curvature structures and illumination conditions. This work therefore provides a useful tool for concrete slabs crack detection and is broadly applicable to variety of infrastructure systems.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.156-157
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• 2021

Since concrete is contaminated or radioactive during operation of nuclear power plants, it is the most important radioactive waste generated during the dismantling of a nuclear power plant. The amount of waste is different depending on the pollution state of each facility and the applied technology is different, so there is a big difference. We aim to reduce the amount of waste and increase the value of recyclability through technology to remove radionuclides attached to the surface. For this purpose, laser scabbling, which exfoliates the surface of concrete by irradiating a laser, and a facility system for controlling dust and dust are used in parallel. The purpose of this study is to evaluate the efficiency of laser scabbling by manufacturing simulated concrete for nuclear facilities, and to review the optimal mixing design conditions for nuclear facility structures.

• Structural Engineering and Mechanics
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• v.38 no.6
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• pp.803-823
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• 2011

In this paper, the three dimensional Parallel Realistic Failure Process Analysis ($RFPA^{3D}$-Parallel) code based on micromechanical model is employed to investigate the bonding behavior in FRP sheet bonded to concrete in single shear test. In the model, the heterogeneity of brittle disordered material at a meso-scale was taken into consideration in order to realistically demonstrate the mechanical characteristics of FRP-to-concrete. Modified Mohr-coulomb strength criterion with tension cut-off, where a stressed element can damage in shear or in tension, was adopted and a stiffness degradation approach was used to simulate the initiation, propagation and growth of microcracks in the model. In addition, a Master-Slave parallel operation control technique was adopted to implement the parallel computation of a large numerical model. Parallel computational results of debonding of FRP-concrete visually reproduce the spatial and temporal debonding failure progression of microcracks in FRP sheet bonded to concrete, which agrees well with the existing testing results in laboratory. The numerical approach in this study provides a useful tool for enhancing our understanding of cracking and debonding failure process and mechanism of FRP-concrete and our ability to predict mechanical performance and reliability of these FRP sheet bonded to concrete structures.

• Journal of Korean Association for Spatial Structures
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• v.10 no.4
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• pp.85-92
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• 2010

Use of concrete has undoubtedly become widespread in construction and civil engineering. Sensors are used to add functional characteristics to concrete. Self-diagnosis concrete is also being developed. The thermal protector used in the study is a sensor using the linear expansion and cubical expansion of metal. The LED(Light Emitting Diode) is a phototransistor type, and to secure high-sensitivity light, the prices of these sensors are low. Rising temperatures of concrete elements can be predicted from LED of the external virtual beam due to operation of thermal protector sensors of concrete beam caused by fire load on the concrete specimen. In this study, the development of fire-diagnosis concrete using composite sensors are the fundamental study for damage detection using simply measurements.