• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1985-1990
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• 2008

1970년대 이후의 고도경제성장기에 치수대책과 동시에 건설골재로서 하상이 굴착된 하천이 많으며, 국가하천 지정구간외에서는 평균하상고가 1.0m 이상 저하한 하천구간도 많다. 또한 국가하천은 상류의 사방공사나 댐건설에 의한 영향이 복합적으로 하도에 나타나고 있어 하상굴착이 하도특성에 어떤 영향을 미치는가를 실증적(實證的)으로 검증하는 것은 어려운 과제이다. 하천에서의 골재채취는 제방부의 침식에 의한 호안파괴, 하상저하에 따른 교량이나 취수보 등 구조물의 기초 노출이 치수적인 문제를 야기할 뿐만 아니라, 단시간내에 하도의 지형구조를 급격하게 변화시켜 여울 소의 하상구조 교란이나 수중 및 하천변의 서식처 파괴 등으로 하천의 물리적 환경에 큰 영향을 미침으로써 생태계를 교란하거나 파괴하는 결과를 초래하게 된다. 본 연구에서는 골재채취로 인하여 교란된 하천의 복원 및 적응관리 계획수립의 전단계에 필요한 교란평가기법을 개발하기 위하여 황강, 남강 및 감천을 대상으로 하여 대조구간과 교란구간을 선정하고 조사 분석하였다. 하천골재 채취가 없거나 경미한 대조구간에서는 홍수량이 변하지 않으면 terrace 모양의 하안부 재료가 하상재료와 거의 같기 때문에 홍수가 있으면 침식된 원래의 하폭으로 회복되는 방향으로 변하지는 않는 경향이 나타났다. 반면에 골재채취가 많은 경우 큰 홍수시의 저수로부의 수심을 증가시키기 때문에 수충부 등의 최심하상고가 크게 되는 경향이 있었으며, 고수부는 침수되는 빈도와 수심이 감소하기 때문에 토사의 퇴적속도(고수부의 상승속도)의 감소, 퇴적물의 세립화 경향이 나타나서 모래, 실트가 퇴적하지 않는 고수부상에 모래, 실트가 퇴적되는 경우가 있고, 반대로 고수부의 퇴적속도가 상승하는 경우도 있었다. 골재채취로 횡단방향의 평탄화가 초래되어 여울 소의 하상구조가 교란됨과 동시에 구간별로 종단경사가 완만해지며, 대부분 교량부에 하상유지공을 설치해야 할 정도로 하상경사가 급변하는 구간이 다수 조사되었다. 또한 선행연구에서 개발된 하상서식환경, 하상재료, 유속/수심상황, 유사퇴적, 하도흐름상태, 하도개수, 여울출현 빈도, 하안 안정성, 식생피복 및 하반림 등 10개의 교란평가항목을 적용하여 대조구간과 비교 평가하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.125-135
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• 2011

The bond properties between polypropylene fiber reinforced cement composites and structural synthetic fiber have been investigated. in this paper. Three levels of polypropylene fibers volume fraction were used, 0.10%, 0.15%, and 0.20% in a series of Dog-bone pull out tests. The bond strength between structural synthetic fiber and polypropylene fiber reinforced cement composites increases with the volume fraction of polypropylene fiber, but the bond strength decreases above the amount of 0.20% by volume of polypropylene fiber reinforced cement composites. Also, the addition of polypropylene fiber a significant improved the interface toughness and the frictional resistance, The microstructure of structural synthetic fiber surface was investigated after the pullout test. The scratched of structural synthetic fiber increased with the polypropylene fiber volume fraction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.19-26
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• 2014

Concrete guide rail and median barrier are an attached RC member, however they are vulnerable to cracking due to slip form construction and large surface of member. In this study, causes and pattern of cracking are analyzed through assessment and NDT (Non-Destructive Technique) evaluation for concrete guide rail and median barrier on highway structure. For this work, analysis on drying shrinkage and hydration heat are performed considering installation period, and plastic shrinkage is also analyzed considering their environmental conditions. From the evaluation, plastic settlement around steel location, drying/ plastic shrinkage, and aggregate segregation are inferred to be the main causes of cracking in the structures. The crack causes and patterns are schematized and techniques of crack-control are suggested. Furthermore concrete guide rail/ median barrier in the bridge on the sea are vulnerable to cracking at early age so that special attentions should be paid at the stages of material selection and construction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.51-58
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• 2014

This paper presents a fire exposure test result to evaluate fire resistance capacity of retrofit method using FRP (Fiber Reinforced Polymer) in reinforcement concrete structure. Especially, this paper focused on near-surface-mounted retrofit method; FRP is mounted into the groove after making a groove in concrete. In the test, main parameters are retrofit method and materials for fire proofing. Spray type of perlite and board type of calcium silicate were considered as external fire proof on surface while particle of calcium silicate and polymer mortar as internal one in groove. By increasing the temperature of inside heating furnace, the transfer of temperature from surface of fire proofing material to groove in specimen was measured. As a result, fire proofing using the board of calcium silicate was more effective to delay the heat transfer from outside than spraying with perlite. It was found that the fire proofing could resist outside temperature of $820^{\circ}C$ at maximum to keep the temperature of epoxy below glass transit temperature (GTT).

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.59-66
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• 2017

In this paper, to protect the piping in nuclear power plants and various plant facilities, we have developed a damper using the friction method and carried out a study to analyze the performance. Friction typed damper means a device for attenuating vibration by generating a frictional force to the bearing and the shaft by applying a compressive force to the MER-Spring. In order to analyze the performance of the damper, the properties of MER-Spring and friction materials were analyzed, a study on the effects of friction was carried out, and the behavior of this equation was established. And, to determine whether deformation of the material and to examine the reliability of the behavior equation established, prototypes was produced and, through a performance test and finite element analysis of a damper made of specimens, they were analyzed. As a result, it is noted that the reliability of the material was confirmed, the coefficient of friction have to be adjusted according to the velocity, cyclic loading test and finite element analysis results show exhibits excellent results. In addition, a review of the dynamic loads in the future shall be performed for the usage in more broad fields.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.1-10
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• 2012

In spite of high resistant to corrosion and its strength, over the last two decades, concerns still remain about the durability of FRP materials under severe environmental and thermal exposures. In this paper, authors experimentally examine the combined degradation by thermal and chemical attacks in heterogeneous FRP rebar be made up with various fibers and resins. Five types of Carbon, Glass and Hybrid FRP rebars had manufactured by different process and surface patterns are adopted for the experiments such as weight change, interlaminar shear strength, SEM and FT-IR analysis. FRP specimens were immersed in alkaline or distilled solution up to 150 days and then thermal exposed on 60, 100, 150 and $300^{\circ}C$ for 30 minutes. From the test results, the degradation of FRP bars are influnced by the resin type and manufacturing process as well as the fiber, and ILSS of exposed FRP bar in solutions is slightly increased in initial stage and then decresed with the passing of immersed time. But, in this test, it is observed that the discrepancy of ILSS between degraded by alkaline solution and distilled water is negligible value.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.101-108
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• 2015

The quantities of heavy weight waste glass have been progressively increased because of the rapid industrialization and the change of quality of life. And, the most of them are not recycled. The heavy weight waste glass have been treated by illegal dumping or being buried in landfills. Meanwhile, in order to ensure the safety of nuclear power plant structure, the excellent construction materials are socially required for shielding performance. Concrete is the most widely used construction material, the huge amounts of natural resources are required to make concrete. So, it is needed to investigate the possibility of recycling of heavy weight waste glass as concrete material ingredient. In this study, the heavy weight waste glass was evaluated for the applicability as fine aggregate of shielding concrete. From the results, when heavy weight waste glass was replaced as fine aggregate of mortar, shielding performance can be improved due to increasing in unit weight of mortar. It showed that the strength decreased according to mixing of heavy weight waste glass, Non-Washed heavy weight waste glass is more advantageous in the strength development than Washed case.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.385-388
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• 2008

Modern society is experiencing a high population density and a centralization of facilities. The clear trends in the construction field are aggrandizement, elevation and specialization of building structures. Such trends require improvements of skills in raising material performances, structuring, planning, designing, and increasing construction capacities. In order to procure high performance materials and construction techniques, a top-quality concrete should be used since it takes up a large part of the material. In recent years, active researches have been done on the ultra high strength concrete. Therefore, this experimental study is strength management to fixed quantity in the field of ultra-strong concrete.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.953-956
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• 2007

"Eco-friendly construction"is an emerging issue in the building industry. Main purpose of the eco-friendly construction is to sustain the health and environment of building residents and to minimize the harmful effect on their environment. Apartment residents have great concern on eco-product, since many cases are reported that Sick Building Syndrome is caused by toxic substance from building materials. Environmental performance is to meet through using the highest grade eco-friendly materials. However, generally eco-friendly materials are more expensive than normal materials. Therefore using eco-friendly materials at public housing project is limited to economical aspect. The purpose of this paper is development of eco-friendly material selection model considered cost efficiency. The selection of Eco-friendly finishing materials and their methods are constructed to consider environmental performance level and cost index compositively. Development of eco-friendly material selection method is economic and reasonable one when public housing is constructed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.1-8
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• 2017

An experimental study is needed a reinforcing method for seismic load to apply for RC structures because a lot of earthquakes have frequently happened in the world and those also collapsed infrastructures or damaged human lives. The reinforcing effect of PolyUrea (PU) appeared to be excellent under blast and impact about RC structures. In this study, Stiff Type PolyUrea (STPU) had developed by manipulating the ratio of the components of prepolymer and hardener of PU. And the durability performance evaluation of STPU for deterioration and chemical resistance has been performed. Acid environmental exposure test and ultraviolet (UV) exposure test have been performed as the durability performance evaluation for STPU. Concrete carbonation exposure test and freezing and thawing test for concrete coated with STPU have been performed. The experimental result showed that STPU has high resisting capacity and durability in all tests. Therefore, STPU would be used as seismic reinforcement materials.