사용후핵연료를 저장하는 볼트체결 저장용기의 격납경계를 형성하는 주된 구성요소는 금속 밀봉재이다. 이러한 금속 밀봉 재는 열과 방사선에 의해 그 성질이 저하된다. 또한, 금속 밀봉재가 강한 열에 장기간 노출되면 크리프 현상이 발생한다. 이러한 크리프는 밀봉시스템에 응력 이완을 가져와서, 결국 밀봉재의 건전성을 해치게 된다. 이러한 응력 이완은 금속 밀봉재의 밀봉성능 저하로 이어지며, 저하의 정도에 따라 저장용기의 누설을 야기할 수 있다. 또한, 볼트 체결력의 감소도 밀봉성능 저하에 영향을 미친다. 본 논문에서는 금속 밀봉재의 격납건전성과 볼트체결력 감소를 평가하기 위해 수행한 가속화 시 험의 결과에 대하여 기술한다. 전 시험기간 동안 각 시편에서의 누설률, 볼트 변형률, 금속 밀봉재 주변 온도를 계측하여 분석하였고, 금속 밀봉재는 저장기간 50년 동안 격납건전성을 유지함을 입증하였다. 또한, 가속화 시험의 타당성에 대해서 기술하였다.

In this study, a motion control problem for the vessel towed by towing ship on the sea is considered. The towed vessel does not have self-control capabilities such that its course stability totally depends on the towing ship. Especially, in the narrow canal, river and congested harbor area, extreme tension is required during the towing operation. The authors, therefore, propose a new control system design method in which the rudder is activated to provide its maneuverability. Based on the leader following system configuration, a nonlinear mathematical model is derived and a backstepping control is designed. By experiment results with nonlinear control framework, the usefulness and effectiveness of the proposed strategy are presented.

The composite PAN fibers which incorporated with CNTs and Titania were prepared by mean of wet spinning. These fibers were then pre-oxidized with microwave heating in an air atmosphere. A combination of characterizations was carried out to study the impact of nanoparticles fillers on the properties of as-spun fibers and their performance during the microwave pre-oxidation. The addition of an equal amount of fillers made obvious changes in the chemical and crystalline structure, consequently improves the strength, and this could lower the capability to creep over a wide range of temperatures in the subsequent processes. FTIR and NMR analyses results of the pre-oxidized fibers exhibited clear changes in the PAN structure, where the dehydrogenation reaction and the degree of cyclization were investigated. Additional confirmation of the occurrence of cyclization reaction was achieved by XRD and thermal analysis. According to the TGA results, the pre-oxidized CNT1/ Ti-PAN fibers exhibit greater thermal stability suggesting high carbon content and good quality could result in the dependent carbon fibers.

최근 국내 구조물들의 노후화가 진행됨에 따라 구조물 보강과 관련된 연구에 대한 관심이 높아지고 있다. FRP보강은 노후화가 진행되어 성능이 저하된 구조물을 보강하는데 사용되며 주로 유리섬유를 사용한다. 그러나 이 유리섬유는 환경적 재 활용의 문제점이 대두되고 있다. 따라서 본 연구에서는 친환경적이고 내열성이 우수한 현무암 섬유를 활용한 휨 보강 플레이트 적용방법과 기존 FRP 외부부착의 문제점을 해소하기 위하여 연성 코팅용 보강페인트를 활용한 휨 보강 페인팅 적용방법을 통하여 각각의 경우에 대한 3점 휨 시험을 통하여 보강성능을 평가, 비교하였다. 그 결과 BFRP 보강의 경우 무보강 시험체에 비하여 약 1.2배 높은 강성 값을 나타내었고 콘크리트-BFRP 계면 부착력에 의한 연성효과도 나타났다. 반면 연성 코팅 보강페인팅 적용을 통한 휨 보강의 경우, 무보강 시험체에 비하여 약간의 개선효과는 나타났으나 실험체 제작의 오차 등을 고려할 때 실질적인 보강효과는 크게 나타나지 않았다. 따라서 연성 코팅페인팅을 활용한 보강방법의 경우, 향후 다양한 시공조건에 따른 추가연구가 필요할 것으로 판단된다.

In this study, we will develop a hybrid cross-sectional shape of steel inserted type glued-laminated timber that can improve the strength of structural glued-laminated timber and maximize the ductility by using steel plate with excellent tensile and deformation ability. A total of three specimens were fabricated and the flexural performance test was carried out to evaluate the structural performance of the steel inserted type glued-laminated timber. In order to compare the effect of steel inserted glued-laminated timber, one structural glued-laminated timber test specimen composed of pure wood was manufactured. In addition, in order to evaluate the adhesion performance of the steel inserted, one each of a screw joint test specimen and a polyurethane joint test specimen was prepared. As a result, all the specimens showed the initial crack in the finger joint near the force point. This has been shown to be a cause of crack diffusion and strength degradation. The use of finger joints in the maximum moment section is considered to affect the strength and ductility of the glued-laminated timber beam. Polyurethane-adhesive steel inserted glued-laminated timber showed fully-composite behavior with little horizontal separation between the steel plate and glued-laminated timber until the maximum load was reached. This method has been shown to exhibit sufficient retention bending performance.

Recently, studies have been actively conducted on seismic design and improvement of the seismic performance of bridges, buildings, factories, and plants. In particular, heavy items that are being manufactured or waiting to be shipped from factories (such as generators, engines, and boilers) must be equipped with seismic stoppers to prevent them from moving or falling during an earthquake. Seismic stoppers should be suitably determined by the size and weight of these heavy items; however, they have no general design standard. In this study, structural analyses and seismic tests were conducted to evaluate the performance of newly designed seismic stoppers. Structural analysis was performed on three stopper models to estimate the external load at which the yield stress of the material was not exceeded. Based on the analysis results, a seismic test of the stopper was carried out in accordance with the AC156 test method. Finally, product specifications for all three seismic stopper models were determined and their static/dynamic load performance was evaluated.

The vibration control device such as the damper can be used to reinforce the seismic performance of structures. The damper is activated by the deformation of structures during earthquake; however, the deformation of structures is extremely small, causing difficulty in using the damper. Therefore, there is a need for a method capable of amplifying small deformities and transmitting them to the damper. The purpose of this paper is to develop and evaluate a displacement amplification seismic system using cable-pulley. The appropriate cable was selected through a cable tensile performance test and the results of the frame experiment were compared with theoretical displacement amplification ratio values. As a result, it may be said that the proposed system using cable-pulley is useful for displacement amplification.

Analysis of the 2016 Gyeongju earthquake and the 2017 Pohang earthquake showed the characteristics of a typical high-frequency earthquake with many high-frequency components, short time strong motion duration, and large peak ground acceleration relative to the magnitude of the earthquake. Domestic nuclear power plants were designed and evaluated based on NRC's Regulatory Guide 1.60 design response spectrum, which had a great deal of energy in the low-frequency range. Therefore, nuclear power plants should carry out seismic verification and seismic performance evaluation of systems, structures, and components by reflecting the domestic characteristics of earthquakes. In this study, high-frequency amplification factors that can be used for seismic verification and seismic performance evaluation of nuclear power plant systems, structures, and equipment were analyzed. In order to analyze the high-frequency amplification factor, five sets of seismic time history were generated, which were matched with the uniform hazard response spectrum to reflect the characteristics of domestic earthquake motion. The nuclear power plant was subjected to seismic analysis for the construction of the Korean standard nuclear power plant, OPR1000, which is a reactor building, an auxiliary building assembly, a component cooling water heat exchanger building, and an essential service water building. Based on the results of the seismic analysis, a high-frequency amplification factor was derived upon the calculation of the floor response spectrum of the important locations of nuclear power plants. The high-frequency amplification factor can be effectively used for the seismic verification and seismic performance evaluation of electric equipment which are sensitive to high-frequency earthquakes.