In this study, a field bridge test was conducted to find the dynamic properties of cable supported bridges with resilient-friction base isolation systems (R-FBI). Various ambient vibration tests were performed to estimate dynamic properties of a test bridge using trucks in a non-transportation state before opening of the bridge and by ordinary traffic loadings about one year later after opening of the bridge. The dynamic properties found from the results of the tests were compared with an analysis model. From the result of the ambient vibration tests of the cable supported bridge with R-FBI, it was confirmed that the dynamic properties were sensitive to the stiffness of the R-FBI in the bridge, and the seismic analysis model of the test bridge using the effective stiffness of the R-FBI was insufficient for reflecting the dynamic behavior of the bridge. In the case of cable supported bridges, the seismic design must follow the “Korean Highway Bridge Design Code (Limit State Design) for Cable supported bridges.” Therefore, in order to reflect the actual behavior characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure should be proposed.

The performance enhancement of various damping systems from natural hazards has become an highly important issue in engineering field. In this paper, ENTA hysteretic dampers were tested under cyclic loadings to evaluate their performance in terms of ductility and energy dissipation. The test results showed that the hysteretic dampers are effective damping systems to enhance the buildings performance for remodeling and retrofit of buildings. Also, the hysteretic dampers were modeled in FEM(Finite Element Method) structural analysis program. As comparing the computer modeling and the experiment, this study model reflects the nonlinear behavior of steel and derives the hysteresis loop.

Experiments were conducted on the operating characteristics and performance of various types of working fluid, filling amount and heat flow rate of a loop thermosyphon for cooling ESS battery container. As results of performance test on various working fluids, HFE-7100 and R-134a as a working fluids showed unstable operating and low performance due to vapor pressure drop, and performance was improved by increasing the number of vapor lines for reducing a pressure drop. In this study, n-pentane was more stable and showed better thermal performance among various working fluids.

In this study, an experimental study was carried out to evaluate the bond shear performance according to the shear connector between the glue-laminated timber and steel interface. Ten block shear specimens were fabricated according to the configuration of the adhesive surface of wood and steel. In addition, four test specimens were produced according to the main variable shape of the wood-concrete shear connector. As a result of the block shear test, the shear strength of the steel-wood adhesive is shown to have a shear performance greater than the wood-wood shear strength. As a result of the push-out test according to the shape of the shear connector, the shear strength increased linearly with the attachment area. The complete composite behavior between the glued-laminated timber and the steel can be secured.

In this study, the out-of-plane seismic resistance of lightly-reinforced existing walls strengthened with thick RC jacket was investigated. The thick RC jacket with a thickness of 500 mm was placed at one side of the thin existing wall with a thickness of 150 mm. At the interface between the wall and RC jacket, a tee-shaped steel section with a number of anchor bolts and dowel bars was used as the shear connector. To investigate the connection performance and strengthening effects, the cyclic loading tests of four jacketed wall specimens were performed. The tests showed that the flexural strength of the jacketed walls under out-of-plane loading was significantly increased. During the initial behavior, the tee shear connector transferred forces successfully at the interface without slip. However, as the cracking, spalling, and crushing of the concrete increased in the exiting walls, the connection performance at the interface was significantly degraded and, consequently, the strength of the jacketed walls was significantly decreased. The flexural strength of the jacketed walls with tee shear connector was estimated considering the full and partial composite actions of the tee shear connector.

In order to develop the compatible damping device in various vibration source, a hybrid wall-type damper combining slit and friction damper in parallel was developed. Cyclic loading tests and two-story RC reinforced frame tests were performed for structural performance verification. As a result of the 5-cyclic loading test according to KBC-2016 and low displacement cyclic fatigue test, The hybrid wall type damper increased its strength and the ductility was the same as that of the slit damper. In addition, As a result of the two-layer frame test, the reinforced frame had about twice the strength of the unreinforced frame, and the story drift ratio was satisfied to Life Safety Level.

AU(A plus U-shaped) composite beam was developed for reducing the story height in the residential buildings, and saving the cosrtuction cost of floor structures. Structural performance and economic feasibility of the composite beam have been sufficiently approved through the structural experiments and the analytical studies. Fire safety for the practical application of the composite beam has also been verified through the fire resistance tests and the heat transfer analyses. In this study 2-points bending tests were performed on the four specimens already tested for fire resistance to evaluate the residual bending strength of AU composite beam after fire accident. The same bending test was performed on the one fresh specimen having the same section and span of the specimens for practically comparative study.

One simple way of increasing the heat transfer for a fin-and-tube heat exchanger is to increase the fin surface area. In this study, a series of tests were conducted on wide slit fin heat exchangers having an increased fin area (Pl/Pt = 0.87), and the results were compared with those of standard slit fin heat exchangers (Pl/Pt = 0.6). Thermal performances of wide silt-finned samples were superior to those of standard slit fin samples. For one row configuration, the j factor of the wide slit fin sample was 11% larger, and the f factor was 33 % smaller than those of the standard slit fin sample. The difference decreased as the number of tube row increased, although wide slit fin sample always yielded superior performance, The reason was attributed to the many narrower slits formed on the wide fin sample. Furthermore, the effect of fin pitch on j and f factor was not significant, and j factor decreased with the increase of the number of tube row.

현장타설 콘크리트 기초 혹은 흙막이용 파일로 사용되는 강관파일은 일반적으로 원형단면구조를 갖고 있다. 그러나 접합면이 원형이기 때문에 띠장을 용접하는 작업이 어렵고, 다른 접합부재를 곡면으로 가공해야 하므로 작업효율이 떨어지고 내외부 콘크리트의 분리현상으로 인해 구조적인 안전성이 떨어진다. 또한 기존의 H-Pile흙막이 공법의 경우, 엄지말뚝간의 간격이 1m 내외로 강재물량이 증가하고 암반천공 수가 많아져서 공사기간이 늘어나는 문제점이 있다. 이러한 배경에서 본 연구에서는 기존의 흙막이 말뚝이 갖는 제작과 시공상의 문제점을 해결하기 위하여 다각형 폐단면을 갖는 신개념 CIP공법용 흙막이 말뚝을 개발하였다. 이를 위해 띠장 등의 접합용접을 용이하게 하기 위한 단면을 산정하였고, 냉간프레스성형을 통한 다각형단면을 구성을 통해 기존의 H-Pile보다 강한 휨강성을 갖는 Pile을 제작하여 단면성능을 평가하였다. 또한, 폐단면강관 내부에 콘크리트 및 모래 등을 타설하여 채움재로 보강했을 때 Pile의 구조성능을 평가하였다. 그 결과, 제안형 다각형 폐단면을 갖는 합성 파일의 충분한 소성능력과 내력을 확보하고 있었다.

우리나라는 지진으로부터 안전한 국가라는 인식이 형성되었으나 최근 경주와 포항 지진에 의해 발생된 구조물 피해로 구조물 안전성 확보를 위한 관심이 증가하고 있다. 국내 중저층 건축물에 다수 적용되고 있는 철골 모멘트 골조는 기본적인 내진성능을 보유하고 있지만 보-기둥 접합부의 소성변형으로 인한 취성파괴로 다양한 문제를 발생시킨다. 최근에는 이러한 문제를 해결하기 위해 구조물에 상온에서 잔류변형으로부터 원형복원이 가능한 초탄성 형상기억합금의 활용에 관한 연구가 진행되고 있다. 따라서 본 연구에서는 소성변형이 집중되는 보 플랜지 부재에 초탄성 형상기억합금 보강판을 활용한 보–기둥 접합부에 대하여 실험을 통한 실질적인 내진성능을 평가하고자 한다.

기존 내진보강시스템의 문제점을 개선하기 위한 듀얼프레임형 내진보강시스템은 기존구조체, 외부보강체, 댐퍼로 구성된다. 듀얼시스템은 지진발생시 주기차이로 인하여 기존구조체와 외부보강체 사이에서 상대변형이 발생되고 이를 댐퍼가 대응하여 안정적으로 지진에너지를 흡수하여 내진성능을 확보한다. 본 논문에서는 듀얼시스템의 구조성능을 분석하기 위하여 정적반복가력실험을 수행한다. 실험결과, 듀얼시스템 실험체는 비보강 실험체와 유사한 손상상태를 나타내었다. 이와 같이 나타난 이유는 정적실험 시 기존구조체를 강제 이력 시켰기 때문이다. 하지만 하중-변형관계곡선에서 핀칭현상이 완화되는 것으로 나타났고, 안정적인 이력거동을 통하여 비보강 실험체에 비해 5.3배 더 많은 에너지를 흡수하였다. 또한 동일한 층간변형각 및 누적 변형에 대해서도 더 많은 에너지를 흡수할 수 있음에 따라 듀얼시스템을 적용할 경우 내진성능을 향상시킬 것으로 판단된다. 또한 듀얼시스템을 실무에 적용하기 위해서는 설계프로세스 등에 대한 연구가 필요하며, 본 논문을 추후 연구의 기초자료로 제시하고자 한다.

최근 국내의 지진발생 빈도가 증가함에 따라, 지진피해 저감 시스템 중 가장 효율이 높은 제진방식의 문제점을 해결하며 댐퍼의 복원성과 에너지 소산 능력을 증가시켜 잔류변형 감소와 사용성 증대 효과를 발생시키는 새로운 제진설계 방식이 필요하다. 본 연구에서는 학교 등 기존에 시공된 비내진상세 철근콘크리트 구조물의 지진에 의한 뒤틀림 방지, 횡방향 변위제어 및 진동저감을 위하여 구조물의 양 옆에 원형강봉댐퍼를 설치하는 시스템을 제안하고, 2층 철근콘크리트골조 실험체를 반복횡 하중 가력 하여 내진성능을 평가하였다. 무보강 및 보강 실험체들의 실험결과를 비교한 결과 외부보강용 원형강봉댐퍼 시스템이 2층 철근콘크리트 골조의 강성과 에너지소산면적을 증가시켜 내진성능을 증가시킴을 확인하였다. 또한 원형강봉댐퍼가 지진 에너지를 소산하여 지진력을 흡수함을 확인하였다.

In this study, the performances of the refrigeration unit for the box under actual operating conditions were examined by using the constant temperature and humidity chamber (air enthalpy method). For this purpose, the degree of superheat, pressure, and temperature were measured while changing the EEV opening, the compressor speed, the outdoor temperature, and the load in the refrigeration cycle of the refrigeration unit. The highest cooling performance was found at EEV 33%. However, EEV 35% with low compression ratio and degree of superheat was the most reliable in terms of reliability. Considering the compressor speed and cooling performance, the refrigeration unit was in an optimal condition at the compressor speed 3,040RPM. The results of this study will be provided as basic data for the optimal design of refrigeration units for box.

콘크리트로 채워진 강관기둥은 많은 구조 시스템에서 기둥으로 널리 사용되며 강재가 항복하고 구속효과가 감소하여 국부 좌굴이 발생한다. 이러한 단점을 극복하기 위해 FRP를 보강하여 국부 좌굴을 지연시키는 방법을 제안한다. 이 논문은 반복 압축하에서 FRP로 보강된 CFT의 압축성능에 관한 것이다. 두 가지 유형의 FRP (Aramid FRP, SRF Polyester Belt)가 다양한 보강두께와 겹수로 CFT 외부에서 보강하여 비교 분석된다. 또한, CFRP에서 제안 및 사용된 공식에 기초하여 시험 기관의 실험 값을 평가하고 그것이 사용될 수 있는지를 결정할 것이다.

This experimental study was conducted to investigate the refrigeration cycle performance of a 10kW refrigerator unit using R404A refrigerant. The capacity, COP, and refrigeration cycle of the refrigerator unit were confirmed by changes in refrigerant charging amount and degree of superheat. The cooling capacity and COP of the refrigerator unit showed different tendency according to changes in refrigerant charging amount and degree of superheat. It was confirmed that the performance changes of the refrigerator unit were more dependent on the change in degree of superheat than the refrigerant charging amount. From the capacity, COP, pressure, and p-h diagram, the refrigeration cycle of the refrigerator unit showed the greatest capacity and COP at 4℃ for degree of superheat and 7,400g for the refrigerant charging amount.