강재를 대처할 수 있는 다양한 복합재료 중 CFRP (Carbon Fiber Reinforced Polymer)를 사용하여 인장 물성 실험을 실시한다. KS F ISO 10406 (콘크리트용 섬유강화 폴리며(FRP 보강재 - 시험방법) 에서 FRP의 측정길이는 지름 (D)의 40 배를 기준으로 제시되어진다. 그러나 25 mm 이상의 시험체는 양단 보강부를 포함하게 된다면 대략 2 m 이상으로 제작되어지게 되고 시험이 상당히 번거롭게 됨으 로써 시험법 개선을 위해서 측정 길이별로 설정하여 성능평가 후 비교분석 한다.

PSC 공법으로 시공된 구조물에서 긴장력을 도입시키는 주요 재료인 PS 강연선은 뛰어난 성능을 보 유하고 있으나, 강재로 제작되어 부식에 취약한 단점 또한 가지고 있다. 이에 한국건설기술연구원에서 는 PS 강연선을 대체할 목적으로 비부식 탄소섬유 케이블을 개발하고 있다. 비부식 탄소섬유 케이블은 PSC 구조물에 사용될 목적으로 개발하고 있기 때문에 인장강도 등 단기 성능 외에도 크리프 및 릴랙 세이션 등 장기 성능 또한 보유하고 있어야 한다. 따라서 본 연구에서는 하중을 일정하게 유지시킨 상 태로 시편의 변형을 살펴보는 크리프 시험과 변위를 일정하게 고정시킨 후에 도입된 하중의 변화를 살펴보는 릴랙세이션 시험을 수행하여 탄소 섬유 케이블의 장기 성능을 검증해 보았다. 각 시험을 수 행하고 데이터를 분석한 결과, 본 연구에서 개발한 탄소섬유 케이블은 크리프와 릴랙세이션에 대해서 일반적으로 PSC 구조물에 사용되는 PS 강연선에 비해 동등 이상의 성능을 보유하고 있는 것으로 판 단된다.

이 연구에서는 CFRP 케이블의 압착형 정착장치의 강종에 따른 피로성능을 평가하였다. 실험결과, CFRP 케이블 압착형 정착시스템은 정착장치의 강종에 상관없이 도로교설계기준의 포스트텐션용 정착 구에 대한 피로시험 조건을 만족시켰다. 그러나 피로시험이후 인장성능 실험에서 SM45C 강종의 정착 장치는 최대내력 도잘전에 케이블과 정착장치 사이에서 미끄러짐이 발생하였으며, 듀플렉스 강종의 정 착장치는 최대 내력 도달과 동시에 CFRP 케이블이 파단되었다.

본 연구에서는 광섬유를 이용한 탄소섬유복합재료(CFRP) 긴장재 개발을 목표로 다양한 성능실험을 수행하였다. 광섬 유 센서를 활용한 탄소섬유 긴장재의 계측성능은 부착된 변형률 게이지의 계측 값과 비교한 결과, 3.7% 이내로 동일한 계측을 하는 것으로 나타났고, 탄소섬유 긴장재 파단까지 계측이 가능하기 때문에, 센싱용 긴장재로 활용이 가능함을 확인하였다. 현장 적용을 위한 장기성능 실험결과, 릴렉세이션의 경우 저릴렉세이션 강연선 기준 값인 2.5%를 만족하였고 피로시험의 경우 도로 교설계기준을 준용하여 200만회 이후 인장성능의 변화가 없는 것을 확인되어, 탄소섬유 긴장재 뿐만 아니라 정착구도 장기성능 을 확보한 것으로 판단된다

본 논문은 콘크리트 구조물 보강공법 중 하나인 CFRP 표면매립 긴장보강의 거동을 분석하였다. 이를 위해 CFRP 긴장재 및 긴장시스템을 개발하고 손상후 보강거동 및 충전재 유무에 따른 비부착 보강거동을 고찰하였다. 실험결과, 비부착 실험 체의 보강효과는 무보강 실험체보다 38% 증가하지만, 부착 실험체보다 17% 감소하였다. 손상된 콘크리트를 보강한 경우는 건전한 콘크리트의 보강효과와 유사했다. 정착장치와 부착된 CFRP 긴장재는 안정된 보강효과를 보였다.

콘크리트는 안전성과 경제성이 우수한 재료로 인식되어 많은 사회기반시설물의 건설재료로 이용되어 왔으나, 최근에는 노후화 현상 등으로 인한 성능저하가 발생하고 있으며 이는 직·간접적으로 경제적·인명적 피해의 원인이 되기 때문에 여러 가지 보강을 실시하고 있다. 본 연구에서는 복합섬유소재를 활용하는 보강공법을 포함한 다양한 보강공법에 대한 성능비교 실험연구를 수행하고 분석하였다.

Using computational fluid dynamics (CFD), this study simulated the air supply and exhaust conditions inside KTXSancheon train cabin to analyze the airflow, velocity, temperature, and residence time distributions. Based on the analyzed airflow in the cabin, the trajectory properties of droplets with various diameters exhaled from a passenger in a specific seat were analyzed. In the train cabin, forced airflow was formed by the operation of an air conditioning unit, while air stagnation occurred through spinning vortices at the front and rear where there were no floor outlets. Droplet particles ≤36 μm in diameter were dispersed throughout the cabin following the airflow generated by the air conditioning unit. The degree of dispersion differed according to the passenger seat location. In addition, the expelled droplets were mostly deposited on the surfaces of passenger bodies, seats, and floor. The ratio of deposited droplets to suspended droplets was increased with increasing droplet size. Further, the CFD study allowed the prediction of the possibility of exposure to exhaled droplets by estimating the dispersion and deposition properties of droplets released from a passenger in a specific seat. This study can be utilized to adjust the operation of air conditioning units and encourage the installation of air-purifying units to minimize secondary infections.

FRP is a new material that has light, high strength and high durability characteristics and is emerging as a third construction material in and out of countries. However, very few studies have been done on curved FRP construction materials that can be used for tunnels or arched bridges. In particular, many joints are required for the application of curved panels to the open cut tunnel. Experimental data on the performance of the joint is required due to insufficient design criteria. The purpose of this study is to analyze the structural performance of real size, composite materials curved panels. To achieve this goal, curved panels were constructed and bending performance was tested. A numerical analysis was also performed and compared with the results of the test. The results of the test showed that the average load was 757.6 kN and the average displacement of bottom was measured at 53.12 mm. Compression stress on the upper flange and tensile stress on the lower flange were within acceptable limits of 50% of the allowable stress.

This paper is focused on an economic analysis of applied air pollutant control technologies used for the particulate matters present in subway. Beneficial effects such as reduction in medical expenses and prevention of productivity loss and death are achievable through the adaptation of control technologies. The result showed that the total investment expense was 97.6 billion won and the cost-benefit was 4776.8 billion won, therefore a 4.8 benefit/ cost ratio was attained.

PURPOSES: In this study, we analyzed the compressive strength characteristics of lean base concrete in relation to changes in the outdoor temperature after analyzing the cold and hot weather temperature standards and calculated the minimum and maximum temperatures when pouring concrete. We examined the rate of strength development of lean base concrete in relation to the temperature change and derived an appropriate analysis formula for FRC base structures by assigning the accumulated strength data and existing maturity formula. METHODS: We measured the strength changes at three curing temperatures (5, 20, and 35℃) by curing the concrete in a temperature range that covered the lowest temperature of the cold period, 5℃, to the highest temperature of the hot period, 35℃. We assigned the general lean concrete and FRC as test variables. A strength test was planned to measure the strength after 3, 5, 7, 14, and 28 days. RESULTS : According to the results of compressive strength tests of plain concrete and FRC in relation to curing temperature, the plain concrete had a compressive strength greater than 5 MPa at all curing temperatures on day 5 and satisfied the lean concrete standard. In the case of FRC, because the initial strength was substantially reduced as a result of a 30% substitution of fly ash, it did not satisfy the strength standard of 5 MPa when it was cured at 5℃ on day 7. In addition, because the fly ash in the FRC caused a Pozzolanic reaction with the progress into late age, the amount of strength development increased. In the case of a curing temperature of 20℃, the FRC strength was about 66% on day 3 compared with the plain concrete, but it is increased to about 77% on day 28. In the case of a curing temperature of 35℃, the FRC strength development rate was about 63% on day 3 compared with the plain concrete, but it increased to about 88% on day 28. CONCLUSIONS: We derived a strength analysis formula using the maturity temperatures with all the strength data and presented the point in time when it reached the base concrete standard, which was 5 MPa for each air temperature. We believe that our findings could be utilized as a reference in the construction of base concrete for a site during a cold or hot weather period.

PURPOSES: As pavement generally provides service shorter than an expected life cycle, maintenance cost increases gradually. In order to help extending the service life and reduce maintenance cost, a new multi-functional composite pavement system is being developed in Korea. METHODS: This study is a part to develop the multi-functional composite pavement and is to investigate the mechanical performances of fiber-reinforced lean concrete for pavement subbase. The inherent problem of fiber reinforced concrete is dispersion of fibers in concrete mix. This study additionally evaluated fiber dispersion characteristics with respect to different fiber types. RESULTS: From the test results, the compressive strengths of the concretes satisfied the required limit of 5MPa at 7days. The standard deviation of the measured number of fibers were lower in the order of nylon, steel fiber and polypropylene. CONCLUSIONS: Reject ash was shown to be satisfactory as a replacement material to Portland cement in lean concrete base. The fiber volume fraction is suggested to be 0.4% even though the fracture toughness did not vary significantly with respect to fiber types. However, fracture energy absorbed up to complete failure increased with the increased fiber volume fraction increment.

PURPOSES : The purpose of the study was to examine dynamic features of concrete after mixing a little macro fiber with small aspect ratio and long length utilized for bridge, tunnel and shotcrete for tensile performance and crack control in domestic/overseas countries with cement concrete pavement mix. METHODS : Coarse aggregates with small aspect ratio and macro fibers with maximum length of approximately 32 mm are introduced in small quantities in the mix proportions of concrete pavement so as to prevent loss of the workability. Then, this study intends to evaluate the applicability of macro fibers in the mix proportions of concrete pavement by examining the basic construction performance, as well as the change of toughness, the equivalent bending strength and the flexural toughness index caused by compression, bending, tension and the flexural stress-displacement curve. RESULTS : As the results, in each kind of macro fiber, polyvinyl alcohol fiber and steel fiber displayed a good performance. CONCLUSIONS : In 0.2 and 0.3% of fiber contents, it is appeared that polyvinyl alcohol fiber has a large effect on improvement of tensile performance and steel fiber on improvement of deforming performance of bending stress.

PURPOSES: This study is to investigate the mechanical performance of the fiber reinforced lean concrete with respect to different types of fibers. METHODS: Increased vehicle weight and other causes from the exposed conditions have accelerated the deteriorations of road pavement. A new multi-functional composite pavement system is being developed recently in order to extend service life and upgrade the pavement. A variety of tests were conducted before and after hardening of the concrete. RESULTS: From the test results, it was found that the use of different types of fibers did not affect the compressive strength development. This might be due to the inherent property of the lean concrete. When steel fibers were used relatively greater flexural strength and flexural fracture toughness were developed. Also addition of fly ash by replacing a part of Portland cement the fracture toughness was slightly increased. CONCLUSIONS: It has been known that the addition of fibers and use of mineral admixture can be positively considered in the development of multi-functional composite pavement system as its required mechanical performance is obtained.

In this study, the fatigue behavior of reinforced concrete beams strengthened with prestressed NSM CFRP tendons. One of test objectives is to find out strengthening effect with concrete strength 20MPa, 40MPa. As a result of the study, the fatigue behavior of the concrete beams strengthened with prestressed NSM CFRP tendons were considered to be good.

This paper carried out experiments on reinforced concrete beams strengthened with prestressed NSM CFRP tendons. One of test objectives is to find out strengthening effect with concrete damage rate 0%, 30%, and 60%. Test revealed that strengthening performance of specimens with 30% and 60% presented similar to 0% strengthening specimen.

콘크리트 구조물은 시간의 경과에 따라 노후화되고, 열악한 외부 환경에 노출되어 부재 및 재료 자체의 성능이 저하된다. 콘크리트 구조물의 유지관리 방안으로 긴장력을 도입한 CFRP 긴장재를 콘크리트 내부의 표면매립(Near Surface Mounted, NSM)하여 구조물의 보수 보강을 위한 연구가 진행 중이다. 기존의 표면매립공법에 대한 연구는 긴장력을 매개변수화 하여 보강성능을 비교하는 연구가 대부분이나 표면매립공법의 파괴거동을 예측할 수 있는 3차원 유한요소해석모델에 대한 연구는 부족한 실정이다. 본 연구에서는 CFRP 긴장재와 콘크리트 부재의 계면 특성을 반영한 3차원 유한요소해석을 통해 포스트 텐션 표면매립공법의 휨 거동을 분석하였다. 또한, 포스트 텐션을 적용한 표면매립공법의 보강성능에 대한 정확한 평가를 위하여 부재단위 실험결과와 제안한 해석모델의 파괴거동을 비교분석하여 타당성을 검증하였다.