• 한국전기전자재료학회논문지
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• 제35권3호
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• pp.269-274
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• 2022

We prepared carbon nanotube (CNT) paper by a vacuum filtration method for the use of a chip-typed resistor as a precision passive device with a constant resistance. Hybrid resistor composed of the CNT resistor with a negative temperature coefficient of resistance (T.C.R) and a metal alloy resistor with a positive T.C.R could lead to a constant resistance, because the resistance increase owing to the temperature increase at the metal alloy and decrease at the CNT could counterbalance each other. The constant resistance for the precision passive devices should be maintained even when a heat was generated by a current flow resulting in resistance change. Performance reliabilities of the CNT resistor for the precision passive device applications such as electrical load limit, environmental load limit, and life limit specified in IEC 60115-1 must be ensured. In this study, therefore, the rated power determination and T.C.R tests of the CNT paper were conducted. -900~-700 ppm/℃ of TCR, 0.1~0.2 A of the carrying current capacity, and 0.0625~0.125 W of the rated power limit were obtained from the CNT paper. Consequently, we confirmed that the application of CNT materials for the precision hybrid passive devices with a metal alloy could result in a better performance reliability with a zero tolerance.

• 한국강구조학회 논문집
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• 제19권6호
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• pp.703-714
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• 2007

본 연구에서는 수치해석에 의해 일정 축력을 받는 콘크리트충전 각형강관(각형 CFT) 기둥의 내화성능을 평가하였다. 본 연구에 앞서 각형 CFT 기둥의 실대 내화성능평가 실험을 수행하였으며, 이로써 무내화피복 상태에서 CFT 기둥 자체만의 내화성능을 평가하였다. 강관은 SPSR 400 강재를 사용하였으며 강관 내에는 27.5MPa와 37.8MPa 강도의 콘크리트를 사용하였다. 콘크리트 강도, 작용 하중비와 기둥단면 직경을 변수로 설정하였다. 수치해석에 의해 예측된 내화성능의 타당성을 검증하기 위하여 실험결과값과 비교 평가해 본 결과, 해석값과 실험값이 서로 잘 일치하거나 해석값이 약간 저평가하고 있음을 확인하였다. 따라서 본 수치해석에 의한 CFT기둥 내화성능 예측은 타당하다고 판단된다. 내화성능 영향인자의 분석 결과, 축력비($N/N_c$)가 동일한 경우 콘크리트 강도가 적을수록 내화성능이 우수하며 단면직경이 클수록 내화성능은 향상되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.262-267
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• 2004

The unloading compliance method is the most commonly used method to evaluate the fracture resistance characteristics of a material. In dynamic loading condition, the direct current potential drop(DCPD) method has been used because the unloading compliance method can not be applied due to the discontinuity of loading. However, even in the dynamic test using DCPD method, there is a problem that the voltage drops sharply on the initiation of crack. For the reason metioned above, the normalization method was suggested on ASTM E 1820 which is revised recently, as a new method to evaluate the dynamic fracture resistance characteristic. The nomalization method can be used to obtain a fracture resistance curve directly from a load-load line displacement. In this study, we obtained two fracture resistance curves from static test of welding part of nuclear piping both by unloading compliance and nomalization method. The two curves were almost same each other, so the adaptability of the nomalization method has been proved. We conducted a dynamic fracture resistance test for the same material. The fracture resistance curve from the dynamic test was obtained by normalization method and compared to that of the static test result.

• Steel and Composite Structures
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• 제14권3호
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• pp.295-312
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• 2013

In this paper, a simplified approach based on critical temperature for fire resistance design of steel-concrete composite beams is proposed. The method for determining the critical temperature and fire protection of the composite beams is developed on the basis of load-bearing limit state method employed in current Chinese Technical Code for Fire safety of Steel Structure in Buildings. Parameters affecting the critical temperature of the composite beams are analysed. The results show that at a definite load level, section shape of steel beams, material properties, effective width of concrete slab and concrete property model have little influence on the critical temperature of composite beams. However, the fire duration and depth of concrete slab have significant influence on the critical temperature. The critical temperatures for commonly used composite beams, at various depth of concrete and fire duration, are given to provide a reference for engineers. The validity of the practical approach for predicting the critical temperature of the composite beams is conducted by comparing the prediction of a composite beam with the results from some fire design codes and full scale fire resistance tests on the composite beam.

• 한국강구조학회 논문집
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• 제20권5호
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• pp.655-663
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• 2008

본 연구에서는 콘크리트충전 원형강관(원형 CFT)기둥의 내화성능을 평가하기 위하여 수치해석을 수행하였다. 강관은 SPSR 400 강재를 사용하였으며 강관 내에는 27.5MPa와 37.8MPa 강도의 콘크리트를 사용하였다. 콘크리트 강도, 작용 축력, 단면 직경을 변수로 설정하였다. 수치해석의 정확성을 검증하기 위하여, 기존의 각국 내화성능설계식들에 의한 계산 결과값과 비교 평가 하였다. 또한, 기존의 실대 원형 CFT기둥의 내화성능 평가 실험 결과와 함께 비교 분석하여 수치해석의 타당성을 검증하였다. 원형 CFT기둥의 내화실험 및 수치해석적 연구를 통해 도출된 내화저항시간과 축력비, 단면직경, 콘크리트 강도의 영향을 각형 CFT기둥의 내화성능과 비교 분석하여 각 영향인자들의 영향을 평가하였다. 본 연구의 수치해석적 연구는 실험결과와 비슷한 거동 및 내화성능을 보였다. 따라서 본 연구에서의 수치해석에 의한 CFT기둥의 내화 성능 예측은 타당하다고 판단된다.

• 한국지반공학회논문집
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• 제34권11호
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• pp.107-119
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• 2018

PHC말뚝, 확장판 선단부착 PHC말뚝, 강관 선단부착 PHC말뚝을 현장 시험 부지에서 시험시공하였다. 이들 선단변형 PHC말뚝들에 대하여 하중전이측정이 수반된 연직압축정재하시험을 실시하였으며 시공직후 항타후 동재하시험을 수행하였다. 또한 선단부만 그라우팅한 선단변형PHC말뚝에 대한 연직압축정재하시험도 실시하였다. 3가지 다양한 선단말뚝들 즉, PHC말뚝, 확장판 선단부착 PHC말뚝, 강관 선단부착 PHC말뚝의 하중-침하량 거동은 거의 동일한 양상을 나타내었다. 따라서 말뚝이 선단지지층에 근입된 길이가 동일하고 말뚝 본체의 직경이 동일할 경우 확장판 선단부착 PHC말뚝 및 강관 선단부착 PHC말뚝의 지지력 증대 효과는 거의 없는 것으로 나타났다. 최종재하하중단계에서 PHC말뚝, 확장판 선단부착 PHC말뚝, 강관 선단부착 PHC말뚝의 주면마찰력은 각각 전체 재하하중의 95.8%, 95.6%, 97.8%를 분담하였으며, 선단지지력은 전체 재하하중의 4.2%, 4.4%, 2.2%를 분담하였다.

• 한국지반공학회논문집
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• 제23권8호
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• pp.107-116
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• 2007

하중저항계수설계법(LRFD)은 세계적으로 지반공학적 설계의 실무에서 사용이 증가하고 있으며 머지않아 현재의 허용응력설계법(ASD)을 완전히 대체할 것으로 예상된다. 하중저항계수설계법은 신뢰도해석(Reliability analysis)을 바탕으로 파괴확률을 정량화하여 상부구조물과 하부구조물을 일관된 신뢰도 수준으로 설계할 수 있게 하는 장점을 가지고 있다. 현재 암반에 근입된 현장타설말뚝의 저항계수는 단지 무결암 상태일 경우에 대하여 AASHTO에 의해 제시되어 있다. 그러나 국내의 경우, 말뚝이 근입되는 대부분의 기반암은 심하게 풍화되어 있다. 따라서 본 연구에서는 풍화암(흔히 IGM)에 대한 저항계수를 산정하고자 하였다. 이를 위해 국내 풍화암에 근입된 현장타설말뚝의 저항계수를 산정하기 위하여 신뢰도 해석을 수행하였다. 4개 현장에서 수행된 21본의 재하시험자료가 분석에 사용되었으며, 말뚝지지력을 계산하는 방법에 따라 저항계수는 $0.1{\sim}0.6$의 범위 내에서 산정되었다.

• Advances in environmental research
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• 제12권1호
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• pp.1-15
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• 2023

Wastewater of anthropogenic origin is known to harbor various bacteria that are known to be of potential risk to human health and environment. It is of utmost importance to monitor such water sources. Coliforms present in the sewage water samples of municipal sewage treatment plants located at three different places in the South Gujarat region (Surat, Navsari and Vapi) of India were analyzed for their coliforms load as well as tested for their drug resistance. Using cultivation-based techniques microbial load and drug resistance (Amoxicillin, Tetracycline, Ciprofloxacin, Erythromycin, Trimethoprim and Sulphamethoxazole) were analyzed. Water treatment statistically significantly decreased the bacterial load in Vapi and Navsari samples. The optical density of with and without antibiotics of all the three locations was shown to increase significantly after 72 hours. Of all the isolates tested, except isolate 'VA5' (resisted up to 90 ㎍ of Ampicillin) all other isolates resisted 256 ㎍ concentration of antibiotics tested. This study indicates that the sewage water is being contaminated with drugs and/or antibiotics due to industrial and/or anthropogenic activities. Regular monitoring of the water quality is required followed by implementation of environmental laws for reducing the pollutants, that are of human health and environment concern.

• 대한건축학회논문집:구조계
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• 제36권5호
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• pp.137-146
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• 2020

In this study, an experimental research was performed to find the characteristics of the lateral load resistance of perforated steel plates which could be developed to retrofit existing RC framed buildings. The Specimens are tested with variables such as aspect ratio of plate, the ratio of perforation area, and the ratio of perforated diameter to strip which is more than 0.6. The lateral load was applied with displacement control until to reach 3.5% drift ratio. Through the experimental results, it was shown that the maximum strength of all specimens were reached at around 0.5% drift ratio and maintained until 3.5% drift ratio. From results, the modified strength prediction formula was derived with the variable ratio of the perforated diameter to strip. To evaluate seismic retrofit performance of RC frames using perforated steel plate, a simple design process was presented.

• Earthquakes and Structures
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• 제26권6호
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• pp.489-499
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• 2024

Infill masonry walls are vulnerable to lateral loads, including seismic, wind, and concentrated push loads. Various strengthening metal fittings have been proposed to improve lateral load resistance, particularly against seismic loads. This study introduces the use of post-compressed wedges as a novel reinforcement method for infill masonry walls to enhance lateral load resistance. The resistance of the infill masonry wall against lateral-concentrated push loads was assessed using an out-of-plane push-over test on specimens sized 2,300×2,410×190 mm³. The presence or absence of wedges and wedge spacing were set as variables. The push-over test results showed that both the unreinforced specimen and the specimen reinforced with 300 mm spaced wedges toppled, while the specimen reinforced with 100 mm spaced wedges remained upright. Peak loads were measured to be 0.74, 29.77, and 5.88 kN for unreinforced specimens and specimens reinforced with 100 mm and 300 mm spaced wedges, respectively. Notably, a tighter reinforcement spacing yielded a similar strength, as expected, which was attributed to the increased friction force between the masonry wall and steel frame. The W-series specimens exhibited a trend comparable to that of the displacement ductility ratio. Overall, the findings validate that post-compressed wedges improve the out-of-plane strength of infill masonry walls.