• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.441-444
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• 2006

The Yang Pyeong bridge is high the occurred possibility of temperature crack by means of hydration Heat when the foundation of is constructed. Therefore, a pipe-cooling method was applied for reducing the temperature crack. Using the measured temperature curve when construction was carried out, the measured value and different facts were analyzed. In this paper, cause and analysis with respect to a mentioned above is to discuss firstly, and thermal characteristics of concrete and construction method hereafter is also discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.385-386
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• 2009

The temperature crack of concrete structure is caused by the phenomenon which the concrete volume is restricted in the inside or outside part due th the temperature variations induced by the hydration heat of cement. And mass concrete structures are weak in temperature crack. This study performed the hydration heat analysis of Seongdeok dam to analyze the hydration heat according to different interval of placement.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.287-288
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• 2006

Cracks on the cylinder block of diesel engines will often happen due to cyclic load and thermal stress. According to the Classification Societies' rules, welding repairs of cylinder block made of cast irons are generally not permitted. However, such welding repairs became inevitable taking enormous cost and time for their renewal into consideration. In this study repair welding methods for the cylinder blocks, made of gray cast irons were reviewed and the tests of their welds were carried out in order to purpose the repair welding methods of packing seat and o-ring seat of cylinder block and apply them to the practice. It is concluding remarks that the suspected crack by a magnetic particle test due to different magnetic permeability can be identified, which are not associated with a mechanical discontinuity.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.238-243
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• 2000

The effect of the temperature, the fatigue and the test speed on DEN(double edged notch) specimen which was made by the pp-rubber composites during fracture was stuied. DEN specimen was made on PP-rubber composites through the injection molding. With increasing temperature the fracture strength is linearly decrease and the fracture energy is first increase by $0^{\circ}C$ and after that decrease. In the same temperature the fracture strength during increasing the notch radius is hardly increase. The fracture behaviour at low and high test speed is different entirely. At high test speed plastic region is small and fracture behaviour was seen to brittle fracture tendency. The deformation mechanism of polypropylene-rubber composites during fracture was studied by SEM fractography. A strong plastic deformation of the matrix material ahead of the notch/crack occured. The deformation seem to be enhanced by a thermal blunting of the notch/crack.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.2
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• pp.115-127
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• 2014

Addition of fibers in cement or cement concrete may be of current interest, but this is not a new idea or concept. Fibers of any material and shape play an important role in improving the strength and deformation characteristics of the cement matrix in which they are incorporated. The new concept and technology reveal that the engineering advantages of adding fibers in concrete may improve the fracture toughness, fatigue resistance, impact resistance, flexural strength, compressive strength, thermal crack resistance, rebound loss, and so on. The magnitude of the improvement depends upon both the amount and the type of fibers used. In this paper, locally available waste fibers such as coir fibers, sisal fibers and polypropylene fibers have incorporated in concrete with varying percentages and l/d ratio and their effect on compressive, split, flexural, bond and impact resistance have been reported.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1095-1100
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• 2000

Concrete structure often exhibit cracks due to the combination of material construction and design error. Minor crack can be tolerated depending on exposure condition, but major cracks are aesthetically unpleasant and affect the durability and safety of the structure. All of the reinforced concrete structure have many inevitable cracks for various reason such as drying shrinkage, heat liberation of cement and over loads. Epoxy resin injection widely used for repairing cracks in concrete is too sensitive to high temperature. Besides, the problem in the epoxy resin injection is the difficulty of quality control after execution. Whereas, Ultra Fine Cement is similar in coefficient of thermal expansion and modulus of elasticity to concrete. The objective of the study is to find out that it is possible for Ultra Fine Cement to be used for repairing cracks in reinforced concrete.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.251-258
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• 2003

The early -age behavior of base restrained reinforced concrete (RC) walls is analyzed using a three-dimensional finite element method in this study. After calculating the temperature and internal relative humidity variations of an RC wall, determination of stresses due to thermal gradients, differential drying shrinkage, and average drying shrinkage is followed, and the relative contribution of these three stress components to the total stress is compared. The mechanical properties of early-age concrete, determined from many experimental studies, are taken into consideration, and a discrete reinforcing steel derived using the equivalent nodal force concept is also used to simulate the cracking behavior of RC walls. In advance, to Predict the crack spacing and maximum crack width in a base restrained RC wall, an analytical model which can simulate the post-cracking behavior of an RC tension member is introduced on the basis of the energy equilibrium before and after cracking of concrete.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.73-78
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• 2003

The residual stresses and. distortions of structures by welding exert negative effect on the safety of railroad structures. This investigation performs a thermal elasto-plastic analysis using finite element techniques to evaluate residual stresses in butted-welded joint. Considering this initial residual stresses, local stress and strain at the critical location (weld toe) during the loading were analyzed by elastic plastic finite element analysis. Fatigue crack initiation life and fatigue crack propagation life of butt-welded specimen were predicted by local strain approach and Neuber's role and Paris law. It is demonstrated that fatigue life estimates by local strain approach closely approximate the experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.717-720
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• 2006

The Yang Pyeong bridge is high the occurred possibility of temperature crack by means of hydration Heat when the foundation of is constructed. Therefore, a pipe-cooling method was applied for reducing the temperature crack. Using the measured temperature curve when construction was carried out, the measured value and different facts were analyzed. In this paper, cause and analysis with respect to a mentioned above is to discuss firstly, and thermal characteristics of concrete and construction method hereafter is also discussed.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.876-885
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• 1999

In order to develop high performance basic dam block for tundish vessel in steel-making binders and additives on hydration and thermal characteristics of magnesiz castable refractories were studied. Crack initiation and propagation in cement bonded magnesia castables due to slaking of magnesia clinker at drying process were suppressed by using spinel clinker instead of magnesia powder. In case of Na2O$.$2CaO$.$P2O5(NC2P) bonded castable crack initiation due to slaking of magnesia clinker did not occur but bending strength at high temperature was low. Mechanical properties of NC2P bonded castable refractories at high temperature were improved by using magnesia clinker that contains low SiO2 contents.