교량, 터널 등 콘크리트 구조물의 건설 또는 사용 중 사고는 심각한 재산 및 인명 피해를 야기하기 때문에, 콘크리트 구조물의 증가와 동시에 Structural health monitoring(SHM)의 중요성 또한 높아졌 다. 하지만 현재까지 콘크리트 구조물의 안전 관리 및 유지관리는 주로 인력에 의한 육안 점검이 주를 이루고 있으며, 이는 주관적이고 정성적인 관리 수준에 머무르고 있어 안전성 평가 결과에 대한 신뢰 성 및 실시간 상태 파악과 대응 측면에 한계가 존재한다. 이에 본 연구에서는 현재 활발하게 연구되고 있는 탄소나노튜브를 활용하여 기다란 바 형태의 Carbon nanotube reinforced polymer(CNRP) Bar를 개발하였으며, 이를 콘크리트 구조물에 적용하였다. 구조물 변형에 따른 CNRP Bar의 센싱 성능을 파 악하기 위해 3점 굽힘 시험을 진행하였고, 동시에 콘크리트 구조물 내 CNRP Bar의 전기적 변화를 분석하였다. 실험 결과 콘크리트 구조물에 균열 발생 전 굽힘 응력에 의해 CNRP Bar의 저항이 감소 하였고, 균열 발생 후 균열이 커짐에 따라 저항이 증가하는 거동을 보였다. 이를 통해 CNRP Bar는 콘크리트 구조물에 용이하게 적용할 수 있는 매립형 센서로써 사용 가능하고, 이는 콘크리트 구조물의 안전성을 효율적으로 모니터링하는 시스템으로 발전 가능할 것으로 판단된다.

구조물 보수 부위의 손상, 재 박리 등의 2차 피해가 이어지며, 보수 부위의 새로운 거동 평가 기법 에 대한 연구의 필요성이 대두되고 있다. 현재 구조물 보수 부위의 거동을 알기 위해서 주로 인력 중 심의 구조물 외관 검사를 진행하고 있으나, 단편적인 검사 결과를 얻게 되어 지속적이고 세밀한 점검 이 어려운 실정이다. 따라서, 본 연구에서는 탄소나노튜브 기반 폴리머 콘크리트를 활용해 압축과 같 은 외부 응력에 대한 탄소나노튜브 함량별 전기적 변화를 분석하였으며, 균열이 발생한 콘크리트 구조 물을 보수 후 응력을 가해 거동에 따른 전기적 변화를 평가하였다. 압축 시험 결과, 응력에 따른 탄소 나노튜브 기반 폴리머 콘크리트의 전기 저항이 감소하며, 탄소나노튜브 함량이 낮을수록 응력에 대한 저항 감소 폭이 넓게 나타나며 민감도가 증가하였다. 균열 보수 시험 결과, 보수 부위에 응력이 가해 졌을 때 전기 저항이 감소해 앞서 진행된 실험 결과와 동일한 경향을 보였으며, 또한 응력이 가해지지 않을 때 초기 저항으로 회복하는 경향을 보여 구조물 보수 부위 거동에 대한 평가가 가능한 것으로 검 증되었다. 이를 통해, 탄소나노튜브 기반 폴리머 콘크리트는 구조물에 적용이 가능하며, 구조물 보수 후에도 가해지는 응력에 대한 지속적인 감지가 가능해 보수 부위 거동 평가가 가능할 것으로 판단된다.

The purpose of this study is to experimentally analyze the seismic performance of beam-column specimens with vertical irregular, which were reinforced with RHS (Replaceable steel haunch system). a steel haunch system. To evaluate the seismic performance of the RHS, three specimens were manufactured and subjected to cycle loading tests. Retrofitted specimens have different beam-upper column stiffness ratio as a variable. The stiffness ratio of beam-upper column were considered to be 1.2 and 0.84. As a result of the test, the specimen reinforced with RHS showed improved maximum load and effective stiffness, and energy dissipation capacity compared to the non-retrofitted specimen with same beam-upper column stiffness ratio. The specimen with 0.84 beam-upper column stiffness ratio showed improved performance than the specimen with 12.

By developing molds and facilities to horizontally mold the functional part of the dry-cast concrete block, We intend to develop molds and a series of facilities to horizontally mold the functional part of the dry-cast concrete block to increase production per cycle while maintaining existing production methods and major facilities. In order to do so, CAE analysis is first required to develop molds and facilities for horizontally molding the functional part of the drycast concrete block in the horizontal direction. The procedure will be carried out by reviewing the validity of boundary conditions and physical properties, 3D modeling, grid generation, construction of analysis models, model validity, analysis according to frequency changes, and analysis according to physical properties. First, through the comparison of two-point support, three-point support, and two-point and three-point support in the constraint conditions, We would like to compare it with the actual molded product in the horizontal direction. But first of all, it is considered two-point support in the constraint conditions in this paper.

PURPOSES : Advancements in science and technology caused by industrialization have led to an increase in particulate matter emissions and, consequently, severity of air pollution. Nitrogen oxide (NOx), which accounts for 58% of road transport pollutants, adversely affects both human health and the environment. A test-bed was constructed to determine NOx removal efficiency at the roadside. TiO2, a material used to reduce particulate matter, was used to remove NOx. It was applied to a vertical concrete structure using the dynamic pressurized penetration TiO2 fixation method, which can be easily applied to vertical concrete structures. This study was conducted to evaluate the NOx removal efficiency of the dynamic pressurized-penetration TiO2 fixation method in a test-bed under real roadside conditions. METHODS : A test-bed was constructed in order to determine the NOx removal efficiency using the dynamic pressurized penetration TiO2 fixation method on the roadside. The dynamic pressurized-penetration TiO2 fixation method was applied by installing a vertical concrete structure. NOx was injected into the test-bed using an exhaust gas generator. By installing a shading screen, the photocatalytic reaction of TiO2 was suppressed to a maximum concentration of 1000 ppb along the roadside. The removal efficiency was evaluated by measuring NOx concentrations. In addition, illuminance was measured using an illuminance meter. RESULTS : From the results of the analysis of the NOx removal efficiency in the test-bed which the dynamic pressurized type TiO2 fixation method was applied to, an average removal efficiency ranging from 18% to 40% was achieved, depending on the illuminance. Similarly, according to the results of the evaluation of the NO removal efficiency, an average of removal efficiency ranging from 20% to 62% was achieved. Thus, the NOx removal efficiency increased when the illuminance was high. CONCLUSIONS : From the results of the experiment conducted, the efficiency of NOx removal per unit volume was obtained according to the illuminance of TiO2 concrete along an actual road. Field applicability of the dynamic pressurized-penetration-type TiO2 fixation method to vertical concrete structures along roads was confirmed.

A new clamped mechanical splice system was proposed to develop structural performance and constructability for precast concrete connections. The proposed mechanical splice resists external loading immediately after the engagement. The mechanical splices applicable for both large-scale rebars for plants and small-scale rebars for buildings were developed with the same design concept. Quasi-static lateral cyclic loading tests were conducted with reinforced and precast concrete members to verify the seismic performance. Also, shaking table tests with three types of seismic wave excitation, 1) random wave with white noise, 2) the 2016 Gyeongju earthquake, and 3) the 1999 Chi-Chi earthquake, were conducted to confirm the dynamic performance. All tests were performed with real-scale concrete specimens. Sensors measured the lateral load, acceleration, displacement, crack pattern, and secant system stiffness, and energy dissipation was determined by lateral load-displacement relation. As a result, the precast specimen provided the emulative performance with RC. In the shaking table tests, PC frames’ maximum acceleration and displacement response were amplified 1.57 - 2.85 and 2.20 - 2.92 times compared to the ground motions. The precast specimens utilizing clamped mechanical splice showed ductile behavior with energy dissipation capacity against strong motion earthquakes.

최근 현장작업을 최소화할 수 있는 PC(Precast Concrete) 건축공법의 적용이 급속하게 활성화되고 있다. 그러나 PC 공법은 시공 중, 특히 부재간 일체화 이전에 구조적 성능을 발휘하기 어렵고 완공 후에도 접합부의 일체성을 확보하기 어려워 연쇄붕괴에 취약하다. PC 건축물에서는 다양한 PC 부재간 접합 상세가 존재하며, 국내외 구조/시공 상세가 현격히 다르다. 그러나 국내 PC 시스템의 시스템 과 상세 특성을 반영한 연쇄붕괴에 대한 연구는 매우 미비하다. 따라서, 본 연구에서는 국내에서 주로 사용하는 PC 구조시스템과 접 합부 구조/시공 상세를 조사 분석하였다. 이를 기반으로 국내에서 사용되는 전형적인 PC 시스템의 유형을 설정하고 상기 PC 시스템 의 연쇄붕괴방지성능을 평가하기 위하여 비선형 유한요소해석을 수행하였다. 해석결과를 바탕으로 국내에서 주로 사용된 PC 구조시 스템의 연쇄붕괴방지 성능을 평가하고 구조설계시 고려사항을 제안하였다.

A shake table test is conducted for the three-story reinforced concrete building structure using 0.28 g, 0.5 g, 0.75 g, and 1.0 g of seismic input motions based on the Gyeongju earthquake. Computational efforts are made in parallel to explore the mechanical details in the structure. For engineering practice, the elastic modulus of concrete and rebar in the dynamic analysis is reduced to 38% and 50%, respectively, to calibrate the structure's natural frequencies. The engineering approach to the reduced modulus of elasticity is believed to be due to the inability to specify the flexibility of the actual boundary conditions. This aspect may lead to disadvantages of nonlinear dynamic analysis that can distort local stress and strain relationships. The initial elastic modulus can be applied directly without the so-called engineering adjustment with infinite element models with spring and spring-dashpot boundary conditions. This has the advantage of imposing the system flexibility of the structure on the sub-boundary conditions of springs and damping devices to control its sensitivity in a serial arrangement. This can reflect the flexibility of realistic boundary conditions and the effects of system damping (such as the gap between a concrete footing and shake table, loosening of steel anchors, etc.) in scalar quantities. However, these spring and dashpot coefficients can only be coordinated based on experimental results, making it challenging to select the coefficients in-prior to perform an experimental test.

본 연구에서는 섬유보강콘크리트(SFRC) 구조물의 수치해석을 위한 K&C모델의 보정기법을 소개하였다. SFRC 1축 및 3축 압축강도 실험결과를 기반으로 보정을 수행하였으며, 단일요소 해석결과를 실험결과와 비교함으로써 보정 기법의 검증을 수행하였다. 또 한, 변형률 속도의 영향을 반형하기 위해 동적증가계수(DIF)를 고려하여 SFRC 구조물의 발사체 관통해석을 수행함으로써 보정기법의 적용 가능성을 확인하였다.

PURPOSES : Nitrogen oxides (NOx) are the main precursors to generate fine particulate matter, which significantly contribute to air pollution. NOx gases are transmitted into the atmosphere in large quantities, especially in areas with a high volume of traffic. Titanium dioxide (TiO2), which is a photocatalytic reaction material, is very efficient for removing NOx. The application of TiO2 to concrete road structures is a good alternative to remove NOx. Generally, TiO2 concrete is produced by mixing concrete with TiO2 . However, a significant amount of TiO2 in concrete cannot be exposed to air pollutants or UV. Therefore, an alternative method of penetrating TiO2 into horizontal concrete structures using a surface penetration agent was proposed in a previous study. This method may not only be economical but also applicable to various types of horizontal concrete structures. However, the TiO2 penetration method may not be applied to vertical structures because it has a mechanism for the penetration of TiO2-containing penetration agents via gravity and capillary forces. Therefore, this study aimed to evaluate the applicability of the pressurized TiO2 fixation method for existing vertical road structures. METHODS : For the application of vertical concrete structures — such as retaining walls, side ditches, and barriers — the applicability of a static and dynamic pressurized TiO2 fixation method was evaluated according to the experimental conditions, considering the amount of pressure and time. The penetration depth and distribution of TiO2 particles in the concrete specimen were measured using SEM/EDAX. In addition, the NOx removal efficiencies of TiO2 concrete were evaluated using the NOx analysis system. RESULTS : As a result of measuring the penetration depth and distribution of TiO2 in the concrete, it was found that the surface-predicted mass ratio increased with increasing pressure and time. In the case of the static pressurized fixation method, it was confirmed that a pressure time of at least 10 s at a pressure of 0.2 MPa and 5 s at a pressure higher than 0.3 MPa were required to achieve a NOx removal efficiency higher than 40 %. Conversely, for the dynamic pressurized fixation method applying a hitting energy of 16.95 J, NOx removal efficiencies higher than 50 % were secured in a pressure time of more than 3 s. CONCLUSIONS : The results of this study showed that the static and dynamic pressurized TiO2 fixation method was advantageous in penetrating and distributing TiO2 particles into the concrete surface to effectively remove NOx. It was confirmed that the proposed method to remove NOx was sufficiently applicable to existing vertical concrete road structures.

한본 연구에서는, 철근콘크리트 보 구조물의 동결융해에 따른 장기거동특성 및 최종 파괴형태를 비교 분석하고자 하였다. 철근콘크리트 보 시험체와 재료 시험체를 제작하여, 동결융해 챔버를 이용하여 동결과 융해를 반복적으로 수행하였다. 동결융해를 위하여 기존의 시험법을 참고하여 철근콘크리트 구조물에 대한 시험을 수행 하였다. 동결융해에 따른 콘크리트의 재 료특성 변화와 철근콘크리트 보 구조물의 거동특성 변화를 통하여 동결융해에 대한 영향을 평가하였다. 제안된 동결융해 시험법을 통하여 콘크리트 공시체의 압축강도가 약 19%감소하였다. 철근콘크리트 보 시험체의 경우, 콘크리트의 표면 강도가 동결 융해에 의하여 감소되어 사인장 균열이 발생하여, 재료적 강도 감소에 의한 구조물의 성능이 감소함을 확인하였다. 또한, 사인장 균열이 발생한 동결융해 시험체의 에너지 소산능력이 동결융해를 거치지 않은 시험체와 비교하여 적게 발생하였다.

콘크리트 구조물 절단에 사용되고 있는 다이아몬드 와이어 쏘가 장착된 당김형 절단 장치의 단점을 개선하여 밀기형 절단장치를 개발하였다. 개발된 밀기형 절단장치에는 먼지 집진 커버가 부착되며 마찰열을 냉각하기 위한 건식이나 습식방법을 선택할 수 있다. 개발된 절단장치의 동작특성과 집진 먼지의 누설률 측정을 실험하였다. 시험결과 원활한 동작특성을 보였으며, 먼지의 누설률은 1.7%인 것으로 나타났다. 개발된 절단장비를 사용하여 생물학적 차폐 콘크리트 절단 시 작업자의 내부 피폭선량을 평가하였다. 보수적 평가를 위해 노심 중심부분을 절단하는 경우를 가정하였다. 비방사능이 99.5 Bq·g-1인 누설 먼지로 인해 반면마스크를 착용한 작업자의 예탁유효선량은 0.25 mSv로 평가되었다. 개발된 밀기형 절단장비 사용 시 미량의 먼지 누설률로 인해 작업자의 방사선 피폭이 저감되며, 사용의 편리성으로 세부 절단 계획을 수립할 수 있어 방사성 콘크 리트 폐기물 감량에도 기여할 수 있다. 따라서 원전의 방사화된 생물학적 차폐 콘크리트를 비롯하여 철근 콘크리트 구조물 해체 작업 시 절단 장비로서 사용될 수 있을 것이다.

PURPOSES: Nitrogen oxide (NOx) is a particulate matter precursor, which is a harmful gas contributing to air pollution and causes acid rain. The approaching methods for NOx removal from the air are the focus of numerous researchers worldwide. Titanium dioxide (TiO2) and activated carbon are particularly useful materials for NOx removal. The mechanism of NOx elimination by using TiO2 requires sunlight for a photocatalytic reaction, while activated carbon absorbs the NOx particle into the pore itself after contact with the atmosphere. The mixing method of these two materials with concrete, coating, and penetration methods on the surface is an alternative method for NOx removal. However, this mixing method is not as efficient as the coating and penetration methods because the TiO2 and the activated carbon inside the concrete cannot come in contact with sunlight and air, respectively. Hence, the coating and penetration methods may be effective solutions for directly exposing these materials to the environment. However, the coating method requires surface pretreatment, such as milling, prior to securing contact, and this may not satisfy economic considerations. Therefore, this study aims to apply TiO2 and activated carbon on the concrete surface by using the penetration method. METHODS : Surface penetrants, namely silane siloxane and silicate, were used in this study. Photocatalyst TiO2 and adsorbent activated carbons were selected. TiO2 was formed by the crystal structures of anatase and rutile, while the activated carbons were plant- and coal-type materials. Each penetrant was mixed with each particulate matter reductant. The mixtures were sprayed on the concrete surface using concentration ratios of 8:2 and 9:1. A scanning electron microscopy with energy dispersive X-ray equipment was employed to measure the penetration depth of each specimen. The optimum concentration ratio was selected based on the penetration depth. RESULTS: TiO2 and activated carbon were penetrated within 1 mm from the concrete surface. This TiO2 distribution was acceptable because TiO2 and activated carbon locate to where they can directly come in contact with sunlight and air pollutant, respectively. Infiltration to the concrete surface was easily achieved because the concrete voids were bigger than the nanosized TiO2 and microsized activated carbon. The amount of penetration for each particulate matter reductant was measured from the concrete surface to a certain depth. CONCLUSIONS : The mass ratio on the surface can be predicted from the mass ratio of the particulate matter reductant measurement distributed through the penetration depth. The optimum mass ratio was also presented. Moreover, the mixtures of TiO2 with silane siloxane and activated carbon with silicate were recommended with an 8:2 concentration ratio.