As the capacity of renewable power generation facilities rapidly increases, the variability of electric power system and gas turbine power generation is also increasing. Therefore, problems may occur that require urgent repair while the gas turbine rotor is stopped. When the gas turbine rotor turning is stopped and then restarted, if the turning period is not appropriate, severe vibration may occur due to rotor bending. As a result of the experiment, it was confirmed that normal operation is possible when the gap data measured at the start of rotor turning after maintenance work is similar to the existing value. And the vibration value at the start of rotor turning was lower as the rotor temperature was lower or the stop period was shorter.

PURPOSES : This study investigated the field applicability of pervious concrete to pavement base courses. Pervious concrete was developed at laboratory level, and the compaction methods, field moisture content, and fundamental properties when the material was constructed in the field were studied. METHODS : Field-applied pervious concrete was compacted at different levels using a tandem roller, and cores were taken to investigate the compressive strength, infiltration rate, continued porosity, and freeze-thaw resistance. In addition, the optimum field construction and quality control of the moisture content of a batch plant were measured. RESULTS : The moisture content of pervious concrete has an essential effect on workability and quality control during field test construction. From the test herein, the optimum value at a batch plant was found to be approximately 2.5±0.1%. The compaction level is also a crucial parameter at construction sites because it affects the mechanical and penetration properties. Considering both compressive strength and drainage, the recommended compaction was three times the round trip when a tandem roller was used. The penetration coefficient was 0.88 cm/sec when applying three times the round trip of the tandem roller. The freezing and thawing weight loss rates of the applied pervious concrete satisfied the required condition of 14% or less, regardless the compaction level. CONCLUSIONS : With the suggested mixed proportions of pervious concrete, the recommended compaction was three times the round trip of a tandem roller and a moisture content of approximately 2.5±0.1% from a batch plant. When these conditions were satisfied, the mechanical and drainage properties satisfied the required criteria.

PURPOSES : The objective of this study is to present a practical application method for measuring the setting time of concrete in the field, considering different concrete blending and curing environments. METHODS : In the experimental environment of the concrete setting experiment, a mold was made in the laboratory, and the curing temperature was performed at laboratory room temperature (20-25 ℃), heater (30 ℃), and dryer (40 ℃). In the field, the experimental method was performed in summer and autumn, setting experiments on penetration resistance, ultrasonic pulse velocity, and semi-calorimeter. RESULTS : The result of the concrete setting time experiment was that the early setting time was achieved in the combination of filash and slag when the concrete was mixed, and the setting time in the curing environment was the same as the early setting time in the field. The setting time measurement method shows the correlation of the high crystal coefficient at UPV with 0.99 based on PR and the good ratio of 92 % to 107 % on average. In addition, the semi-calorimeter shows a good crystal coefficient of 0.96 to 0.99 and a good setting time of 88 % to 101 % on average. CONCLUSIONS : The analysis of the setting time of the concrete shows that the curing temperature is more affected than the mixture, and it is considered that the UPV test, which evaluates the reliability of the degree of purification, is easy to sampie among the three methods.

The guarantee of the performance of the engineered barriers in a geological repository is very important for the long-term safety of disposal as well as the efficient design of the repository. Therefore, the performance of the engineered barriers under repository condition should be demonstrated by in-situ experiments conducted in an underground research laboratory. This article provides a review of the major in-situ experiments that have been carried out over the past several decades at underground research laboratories around the world to validate the performance of engineered barriers of a repository, as well as their results. In-situ experiments to study the coupled thermal-hydraulicmechanical behavior of the engineered barrier system used to simulate the post-closure performance of the repository are analyzed as a priority. In addition, in-situ experiments to investigate the performance of the buffer material under a real repository environment have been reviewed. State-of-the art in-situ validations of the buffer-concrete interaction, and the installation of the buffer, backfill and plug, as well as characterization of the near-field rock and the corrosion of the canister materials are, also performed.

As the corrugated steel pipes has many advantages to compensate for the shortcomings of the concrete fume pipes, it has been widely used for culverts and drain trenches. However, when corrugated steel pipes used as a sewage pipe or in an environment exposed to sea water, corrosion can cause problems and degradation of the function of pipe. So, Composite Corrugated Steel Pipe(CCSP) coated with three layers were developed to compensate for the shortcomings and improve performance of corrugated steel pipes. The composite material used in fabrication of the CCSP consists of a three layer polymer protective coating on both sides of a steel sheet core. To verify the field application of the CCSP, a test was conducted on the resistance of the strain, stability of connections, water flow performance and durability to determine whether they meet KS quality and various design standards.

공항 콘크리트 포장 슬래브는 온도와 습도 등 환경요인의 복합적인 영향으로 수축과 팽창을 반복한다. 하지만 슬래브 상·하부간의 비선형적인 온도구배로 인해 깊이에 따른 열팽창률이 다르며, 슬래브 표면에서의 증발로 인한 수분 손실로 인해 부등건조수축이 발생하여 위아래로 뒤틀리는 컬링(Curling)거동을 야기한다. 이처럼 환경요인에 의한 슬래브의 거동은 단기적으로 일주기의 대기 온도변화에 의한 거동특성을 보이며, 장기적으로 건조수축 및 계절적인 온도변화에 의한 거동특성을 보인다. 본 연구에서는 인천국제공항 현장에서의 HWD실험을 통하여 단기 및 장기적인 콘크리트 포장 슬래브의 거동을 예측하고자 하였다. 본 연구를 위해 2016년 11월부로 인천국제공항의 4단계 건설사업 중 3단계 건설사업이 진행중인 여객계류장 현장에 정적 및 동적 계측기를 설치하였으며, 상시적으로 정적변형률을 계측함과 동시에 정기적으로 HWD실험을 통해 동적변형률을 계측하였다. 계절별 거동특성을 분석하기 위해 2017년 3월, 5월, 8월 3차례에 걸쳐 HWD실험을 실시하였으며, 일주기 거동특성을 분석하기 위해 매 실험마다 3시, 7시, 11시, 15시, 21시에 걸쳐 총 5회의 실험을 실시하였다. HWD 실험을 통해 그림 1과 같이 슬래브의 중심, 모서리, 우각부의 내측 및 외측을 대상으로 타격하였으며, 처짐량, 충격강도계수(ISM), 하중전달률(LTE), 포장체 내 변형률, 역산 탄성계수를 조사하여 분석하였다. 현재까지의 HWD실험을 통해 슬래브 거동특성을 분석한 결과 초기상태의 슬래브는 부등건조수축으로 인한 Curl-up이 발생하며, 우각부와 보조기층이 분리된 것으로 예측되었다. 하지만 재령이 지날수록 일정한 Curl-up상태를 유지한 체 보조기층의 침하가 동반되어 Curl-up이 완화되는 거동이 예측되었다. 본 연구진은 추후 추가적인 HWD실험을 실시하여 슬래브 거동 예측결과를 검증 할 예정이다.

Conventional steel and concrete piles are widely applied in civil engineering industries with long time experience and many advantages. However, steel pipe piles, a sort of most common steel pile, are prone to losing their structural integrity over time due to corrosive and humid conditions. Moreover, concrete piles such as in-situ concrete piles and pretensioned spun high strength concrete (PHC) piles are subject to deterioration of their long-term structural durability. Therefore, Hybrid FRP-concrete composite pile (HCFFT) was developed. HCFFT is consisted of pultruded FRP (PFRP) unit module, filament winding FRP which is in the outside of mandrel composed of circular shaped assembly of PFRP unit modules, and concrete which is casted inside of the circular tube shaped hybrid FRP pile. Therefore, PFRP can increase the flexural load carrying capacity, while filament winding FRP and concrete filled inside can increase axial load carrying capacity. In this paper, field loading experiments were conducted to evaluate field bearing capacity of HCFFT pile with connection and HCFFT pile without connection.

OBJECTIVES : A fog generated field test was conducted to analyze the relationship between different sizes of variable speed limit signs and the legibility distance under various fog density conditions. By using this study, appropriate sizes of signs can be selected depending on the density of fog. METHODS : An actual tunnel was selected as the area for this test, as other places cannot maintain the fog condition because of rapid air current. A total 121 subjects were recruited for this test, which took place over the course of four days. The test on the first day was conducted under normal weather conditions for comparison. Visibility-distance detecting sensor was used to measure the visibility distance due to the fog density time, simultaneously with the evaluation of legibility distance by subjects. RESULTS : The test results show the relationship between the different sizes of signs and the legibility distance corresponding to the visibility distance due to both non-fog and fog generated conditions. According to the technical test results, appreciable amount of reduction in legibility distance due to fog was resulted in all sizes of signs. Moreover, the legibility distance is reduced proportionately with the decrease in the visibility distance due to fog. CONCLUSIONS : The results of this study can be used to select appropriate sizes of valuable speed signs under fog conditions. Hence, drivers can expect to have more room to respond to adverse weather conditions, thereby reducing the risk of accidents.

OBJECTIVES : A fog generated field test was conducted to analyze the relationship between the luminance of variable speed-limit signs and the legibility distance under various fog density conditions. By using this study, appropriate luminance values can be selected depending on the density of fog. METHODS: An actual tunnel was selected as the area to conduct the test, as other places cannot maintain the fog condition because of rapid air current. Ninety-two subjects were recruited for this test, which took place during the course of three days. Visibility-distance detecting sensor was used to measure the visibility distance due to the fog density time, simultaneously with the evaluation of legibility distance by subjects. RESULTS: The test results show the relationship between luminance values and the legibility distance corresponding to the visibility distance due to fog. According to the technical test results, lower luminance value such as 7000 cd/m2 corresponds to less legibility distance compared to higher values such as 20000 cd/m2 or 40000 cd/m2. However, the amount of difference between 20000 cd/m2 and 40000 cd/m2 is negligible in our test. CONCLUSIONS: The results of this study can be used to select appropriate luminance of valuable speed signs under fog conditions. Hence, drivers can expect to have more room to respond to adverse weather conditions, thereby reducing the risk of accidents.

This study was performed to improve the foaming generated in the effluent of wastewater treatment plant from March 2015 to July 2016. The main cause of foaming was air entrainment by an impinging jet and the internal accumulation by the diffusion barrier. Particularly, the foam growth was most active when there is low tide and larger discharge. To solve this problem, we experimented after installing fine mesh screen and the artificial channel device with underwater discharging outlet in the treated wastewater discharge channel and the outlet, respectively. As a result, the effects of foam reduction by devices ranged 85.0~92.0% and 70.7~85.6%, respectively. In addition, the foam and the noise were easily solved, first of all look to contribute to the prevention of complaints. Our device studies were applied to a single wastewater treatment plant. However, it is considered to be able to apply in other similar cases of domestic sewage treatment plants.

투수블록은 일반 콘크리트 블록과 다르게 블록 표면 전체에서 물을 투과시키는 블록 또는 특정 위치에서 물을 투과시키는 블록으로 정의된다. 국내 대부분의 도시지역은 불투수성 재료로 포장된 면적의 증가로 인하 여 빗물이 침투될 수 있는 공간이 줄어들고 이로 인해 빗물이 지표로 흡수되지 않아 좁은 우수관으로 빗물이 넘쳐 차량통행에 지장을 주는 한편 도심지 수해발생 증가 및 지하수 고갈의 문제가 발생하고 있다. 미국,일 본 등 국외에서는 수 십 년 전부터 투수성포장이 도입되어 도심 환경을 개선시키는데 일조하고 있다. 최근 국내에서도 투수성 블록이 가진 다양한 장점(도시홍수 예방, 열섬현상 완화, 지하수 함양, 지하생태 보전 등) 이 대두되면서 그 수요가 크게 증가하고 있지만 공용기간에 따른 투수성능 지속성 등에 대한 특성 분석 및 연구가 미진한 상태이다. 2013년「서울시 투수블록포장 설계, 시공 및 유지관리 기준(Ver 2.0)」에서는 차도 용 및 보도용 블록에 대하여 자체투수블록의 경우 보도용 휨강도 4 (MPa) 이상 및 압축강도 16 (MPa) 이상, 차도용 휨강도 5 (MPa) 이상 및 압축강도 20 (MPa) 이상 그리고 틈새투수블록의 경우 보차도용 휨강도 5 (MPa) 이상 및 압축강도 20 (MPa) 이상을 기준으로 하고 있다. 또한 모든 투수블록의 투수계수는 0.1 (mm/sec) 이상을 기준으로 현장에 적용 평가하고 있다. 본 연구에서는 이러한 투수블록의 용도에 따라 현장 에 시공된 보도용･차도용 투수블록의 공용기간에 따른 현장투수성능 지속성을 평가하여 보차도용 투수블록 의 공극막힘 현상, 투수성능 변화 등 보도용 및 차도용 투수블록의 수명예측자료를 확보하고자 하였다. 보차도용 투수블록 투수성 수명예측자료를 통해 투수성능 유지시점을 도출하고 현장에 적용된 투수블 록의 기능을 초기상태로 유지하며 그 고유의 기능이 저하됨이 없이 유지될 수 있기 위한 방안을 검토하고 자 하였다. 또한 현장시험을 통하여 각각의 환경조건인 유동인구 및 가로수 유무, 차량통행 등 환경적인 요인으로 인한 공극막힘현상의 분석을 통해 지속성 검증시험의 효과를 분석하고 초기 투수성능과 공용이 후의 투수성능의 상관성을 분석하였다.

1970년대에 실시된 국토종합개발계획을 시작으로 국내 고속도로망 중 14개의 노선이 건설되었으며, 이 를 바탕으로 고속도로는 운송, 유통 및 생활의 편의성 등 국내 경제성장의 큰 원동력 역할을 수행하였다. 하지만 과거 증설되었던 고속도로가 현재에는 공용수명을 초과한 노후 포장이 되었으며 시간이 지날수록 그 연장이 기하급수적으로 늘어나고 있는 실정이다. 이러한 노후 포장의 경우 유지관리 측면에서의 보수 만으로는 향후 포장의 품질과 경제성 측면에서 한계가 있기 때문에 국내뿐만 아니라 해외에서도 노후 포 장의 처리 및 전략에 대해 다양한 연구가 진행되고 있다. 포장의 리모델링 시급성을 판단하기 위해선 PMS에서 조사하는 항목들을 바탕으로 우선순위를 선정하되 상세 설계를 위한 타당성을 검증하기 위해 선 2차적인 상세조사가 필요하다. 노후 콘크리트 포장에서 주의 깊게 확인해야할 구간을 다음 그림 1과 같이 네 가지 경우로 구분하여 각 해당 구간에서 필수적으로 확인해야할 사항들을 제시하였다. 본 연구는 노선의 리모델링 시급성이 높다고 판단되는 노후 콘크리트 포장에 대해 적절한 상세조사 지 침을 제시하고 이를 활용할 수 있는 방향을 제공하는데 목적이 있다. 또한 리모델링 시급성 지수를 통하 여 선정된 구간에 대해서 본 연구에서 제시한 항목들에 대해 상세조사를 실시함으로서 우선순위 최종 결 정을 실시함을 목적으로 한다.

본 연구는 경사지 밭에서의 토양유실량 저감을 위해 실트펜스와 식생밭두렁의 적용 가능성을 평가하기 위한 현장실험 연구로, 이를 위해 전라북도 익산시 금마면에 시험포장을 설치하고 포장실험을 수행하였다. 시험포장은 표준시험포 크기 (5 m × 22 m), 경사 9%의 시험구 3개소와 정방형 크기(15 m × 15 m), 경사 6%의 시험구 2개소로 구성되어 있으며, 포장에서의 강우량을 측정하기 위해 자기우량계를 설치하였고, 각 시험구의 말단에는 유출량을 측정하기 위한 플륨 및 수위계를 설치하여 모니터링 하였다. 강우시 유출수에 의해 토양이 유실되며 토양 입자에 흡착되어 있는 오염물질도 같이 유출되는데 이러한 유출수의 오염 부하량을 산정하여 토양유실량을 평가하였다. 시간변화에 따라 오염 부하량 저감효과를 분석한 결과 대조구 시험포를 기준으로 실트펜스에서 SS 50.1%가 저감되었고 SS 항목이 저감되었다는 것은 유사가 저감되어 토양유실을 저감시킨 것을 나타낸다. 향후 추가적인 연구를 통해 경사지밭 토양유실량 저감효과를 평가하고 제어대책을 개발하게 되면 밭에서의 토양유실을 최소화시켜 수질개선에 기여할 것으로 사료된다.