• International Journal of Highway Engineering
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• v.15 no.1
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• pp.1-9
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• 2013

PURPOSES: The purpose of this study is to evaluate physical properties, durability, fatigue resistance, and long-term performance of poly-urethane concrete (PU) which can be possible application of thin layer on long-span orthotropic steel bridge and to check structural stability of bridge structure. METHODS : Various tests of physical properties, such as flexural strength, tensile strength, bond strength and coefficient of thermal expansion tests were conducted for physical property evaluation using two types of poly urethane concrete which have different curing time. Freezing and thawing test, accelerated weathering test and chloride ion penetration test were performed to evaluate the effect of exposed to marine environment. Beam fatigue test and small scale accelerated pavement test were performed to assess the resistance of PU against fatigue damage and long-term performance. Structural analysis were conducted to figure out structural stability of bridge structure and thin bridge deck pavement system. RESULTS: The property tests results showed that similar results were observed overall however the flexural strength of PUa was higher than those of PUb. It was also found that PU materials showed durability at marine environment. Beam fatigue test results showed that the resistances of the PUa against fatigue damage were two times higher than those of the PUb. It was found form small scale accelerated pavement test to evaluate long-term performance that there is no distress observed after 800,000 load applications. Structural analysis to figure out structural stability of bridge structure and thin bridge deck pavement system indicated that bridge structures were needed to increase thickness of steel deck plate or to improve longitudinal rib shape. CONCLUSIONS: It has been known that the use of PU can be positively considered to thin layer on long-span orthotropic steel bridge in terms of properties considered marine environment, resistance of fatigue damage and long-term performance.

• Journal of the Korea Institute of Building Construction
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• v.24 no.5
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• pp.577-585
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• 2024

Reinforced concrete structures are vulnerable to the corrosion of reinforcing steel, which is typically caused by the neutralization of concrete and the presence of surrounding chlorides in various environmental conditions. This corrosion leads to cracking in the concrete, thereby reducing durability of the structure and shortening its lifespan. To address this issue, there has been an increasing interest in research on Fiber Reinforced Polymers(FRP), particularly Carbon Fiber Reinforced Polymer(CFRP). CFRP, composed of carbon fibers, is noted for its lightweight properties, outstanding tensile strength, and high elastic modulus. It also offers excellent corrosion resistance and durability against weathering. Despite the potential benefits, the data on CFRP's performance and integration into reinforced concrete structures remain limited. This study contributes fundamental data regarding the application of CFRP, highlighting its advantages and exploring its practical implications. A significant finding from this research is that concrete specimens cured underwater exhibited superior bond strength compared to those cured under dry conditions.

• 한국문화재보존과학회:학술대회논문집
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• 2001.11a
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• pp.19-24
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• 2001

This study mainly reports preliminary results from site investigation of the Great Pyramids and Sphinx in Egypt and sampling works where conducted in the same limestone beds in Mokattam quarry in Cairo. Analyses of composition of samples showed similar result to those of limestone in Giza and thus such samples can be easily used for further experimental work without disturbing real monuments. Future work will be concentrated on the change of engineering properties of samples before and after artificial weathering and the change of digital image acquired from the colored surface of monuments.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.196-203
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• 2008

Durability of geosynthetics for soil reinforcement is accounted for creep and creep rupture, installation damage and weathering, chemical and biological degradation. Among these, the long-term creep properties have been considered as the most important factors which are directly related to the failure of geosynthetic-reinforced soil(GRS). However, the creep test methods and strain limits are too various to compare the test results with each other. The most widely used test methods are conventional creep test, time-temperature superposition and stepped isothermal method as accelerated creep tests. Recently developed design guidelines recommend that creep-rupture curve be used to determine the creep reduction factor($RF_{CR}$) which is a conservative approach. In this study, the different creep test methods were compared and the creep reduction factors were estimated at different creep strain limits of 10% of total creep strain and creep rupture. In order to minimize the impact of creep strain to the GRS structures, the various creep reduction factors using different creep test methods should be investigated and then the most appropriated one should be selected for incorporating into the design.

• Journal of the Korean Solar Energy Society
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• v.30 no.6
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• pp.125-130
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• 2010

Normally, PV system is designed using local weather condition like lowest and highest temperature and irradiance. But this might give misleading results because it is not realistic data of PV module itself. To give more specific description of PV system, we tested photovoltaic(PV) modules' temperature, irradiance and maximum power generation characteristics from January to December in 2008 for 3kW PV system. From this, we could deeply analyze the accumulation temperature, electrical characteristics of PV module in various condition. So precise approach to PV system design can be done. The detail description is specified as the following paper.

• Journal of Korean Association for Spatial Structures
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• v.24 no.2
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• pp.53-63
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• 2024

The cultural heritage of fortresses is often exposed to external elements, leading to significant damage from stone weathering and natural disasters. However, due to the nature of cultural heritage, dismantling and restoration are often impractical. Therefore, the stability of fortress cultural heritage was evaluated through non-destructive testing. The durability of masonry cultural heritages is greatly influenced by the physical characteristics of the back-fille material. Dynamic characteristics were assessed, and endoscopy was used to inspect internal fillings. Additionally, a finite element analysis model was developed considering the surrounding ground through elastic wave exploration. The analysis showed that the loss of internal fillings in the target cultural heritage site could lead to further deformation in the future, emphasizing the need for careful observation.

• Journal of the Mineralogical Society of Korea
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• v.21 no.2
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• pp.183-192
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• 2008

Stone cultural heritages in Korea are mostly situated out door without any notable protection thus there are severe damage from chemical and biological weathering. This in turn, causes deformation and structural damage. To counter act this problem and to increase durability, various kinds of conservation materials are used in the conservation and restoration treatment. However, there are not many practical and technological experiment done on this subject. This paper attempts quantitative evaluation of effectiveness of ethylsilicate based resin for Namsan granite in Gyeongju. When two different materials with different ethylsilicate concentration were compared, the result indicated decrease of absorption and porosity with increase of ultrasonic velocities, uniaxial compressive strength, elastic constant, tensile strength and Poisson's ratio. In addition, comparison of physical characteristic of the conservation material resulted favorably toward ones with higher concentration of ethylsilicate. This is due to the ethylsilicates characteristic to fill the internal pores of stone. There is discolouration of stone surface after treatment with conservation material. This was more prominent with the product of higher ethylsilicate concentration.

• Journal of Conservation Science
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• v.27 no.2
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• pp.211-222
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• 2011

The Mireuksaji stone pagoda was built foundation in the reign of King Moo (AD 639) in the Baekje Kingdom of ancient Korea. The stone properties of the pagoda were quarried from Mountain Mireuk, which are medium to coarse-grained light gray biotite granite formed during the Jurassic, and are composed of quartz, feldspar, biotite, muscovite, apatite and allanite. It was strong relatively but became weak from prolonged weathering, and as a result its durability fell to $883kgf/cm^3$ (moderate weathering degree). In the process, cut-off (31%), deletion (57%) and crack (44%) occurred in foundation materials by the influence of bending, shear and compressive force. Hereat, the original materials were treated through a preservation process. As a result, approximately 74% of original materials have been able to be reused, inclusive of 55 materials that were to be partially replaced by new stones. On the other hand, it is inevitable that the other 26% including exterior stones and support-based stones have to be partially replaced by new stones. It implies that there is a need to find stones that are identical or similar to those of the pagoda. Consequently, a lithological study was conducted on stones in quarries located in Iksan and an investigation was made into their properties. The results showed that stones in the Hwangdeung area were most similar to those of the pagoda mineralogically and their properties were most stable.

• Korean Journal of Heritage: History & Science
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• v.45 no.1
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• pp.86-101
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• 2012

The constituting rocks of Multi-storied Round shape stone Pagoda of Unjusa Temple are lithic tuff and rhyolite tuff breaccia which show green or grey and also rock fragment with poor roundness are present in the structure. lithic tuff is composed of feldspar and quartz which are glassy texture and cryptocrystalline and also micro crystalline are scattered. phenocryst quartz and feldspar in the substrate composed of feldspar and opaque minerals are found in rhyolite tuff breaccia. dust, exfoliation, cavity, fracture and crack are observed in all the stone of the pagoda and the result of Infrared Thermography shows partial inter cavities have developed severely which may cause further exfoliation. In addition, a great deal of various grey, green, and yellow brown lichen as well as bryophyte are present at the upper part of eastern and western roof stone located above the third floor. Discolors remarkably shown at stereobate and roof stone are identified as inorganic pollutants such as manganese oxide, iron oxide and iron hydroxide. The stone of the pagoda of the Chemical Index of Alteration (CIA) and the Weathering Potential Index (WPI) are 55.69 and 1.12 respectively and this corresponds to a highly weathered stage. The measured values, average ultrasonic velocity 2,892m/s, coefficient of weathering 0.4k and compressive strength $1,096kg/cm^3$, suggest that the rock strength and durability are weakened.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.199-212
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• 2021

The Sebyeonggwan Hall (National Treasure No. 305) is located on the Naval Headquarter of Three Provinces in Tongyeong, and it has partly undergone with several rebuilding, remodeling, repairing and restorations since it's the first establishment in Joseon Dynasty (AD 1605) of ancient Korea. This study focuses on 50 foundation stones that comprise the Sebyeonggwan. These stones are made of six rock types and currently have various shapes of the surface damages. As the foundation stones, the dominant rock type was dacitic lapilli tuffs, and provenance-based interpretation was performed to supply alternative stones for conservation. Most of the provenance rocks for foundation stones showed highly homogeneity with their corresponding stones of petrography, mineralogy and magnetic susceptibility. According to surface deterioration assessments, the most serious damages of the stones were blistering and scaling. The deterioration mechanism was identified through the analysis of inorganic contaminants, and the primary reason is considered salt weathering caused by sea breeze and other combined circumstances. Based on the mechanical durability of the stones, there was no foundation stone that required the replacement of its members attributed to the degradation of the rock properties, but conservation treatment is considered necessary to delay superficial damage. The foundation stones are characterized by a combined outcome of multiple petrological factors that caused physical damage to surfaces and internal defects. Therefore, it's required to diagnosis and monitoring the Sebyeonggwan regularly for long-term preservation.