• 제목/요약/키워드: Scaled effect

검색결과 428건 처리시간 0.033초

Experimental investigation of a frame retrofitted with carbon textile reinforced mortar

  • Sinan M., Cansunar;Kadir, Guler
    • Earthquakes and Structures
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    • 제23권5호
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    • pp.473-491
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    • 2022
  • The research investigates experimentally the effect of confinement on structural behavior at the ends of beam-column in reinforced concrete (RC) frames. In the experimental study, five specimens consisting of 1/3-scaled RC frames having single-bay, representing the traditional deficiencies of existing buildings constructed without receiving proper engineering service is investigated. The RC frame specimens were produced to represent most of the existing buildings in Turkey that have damage potential. To decrease the probable damage to the existing buildings exposed to earthquakes, the carbon Textile Reinforced Mortar (TRM) strengthening technique (fully wrapping) was used on the ends of the RC frame elements to increase the energy dissipation and deformation capacity. The specimens were tested under reversed cyclic lateral loading with constant axial loads. They were constructed satisfying the weak column-strong beam condition and consisting of low-strength concrete, such as compressive strength of 15 MPa. The test results were compared and evaluated considering stiffness, strength, energy dissipation capacity, structural damping, ductility, and damage propagation in detail. Comprehensive investigations of these experimental results reveal that the strengthening of a brittle frame with fully-TRM wrapping with non-anchored was effective in increasing the stiffness, ductility, and energy dissipation capacities of RC bare frames. It was also observed that the frame-only-retrofitting with an infill wall is not enough to increase the ductility capacity. In this case, both the frame and infill wall must be retrofitted with TRM composite to increase the stiffness, lateral load carrying, ductility and energy dissipation capacities of RC frames. The presented strengthening method can be an alternative strengthening technique to enhance the seismic performance of existing or moderately damaged RC buildings.

Shear strengthening of reinforced concrete beams with minimum CFRP and GFRP strips using different wrapping technics without anchoring application

  • Aksoylu, Ceyhun
    • Steel and Composite Structures
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    • 제44권6호
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    • pp.845-865
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    • 2022
  • In this study, the performance of shear deficient reinforced concrete (RC) beams with rectangular cross-sections, which were externally bonded reinforced (EBR) with high strength CFRP and GFRP strips composite along shear spans, has been experimentally and analytically investigated under vertical load. In the study, the minimum CFRP and GFRP strips width over spacing were considered. The shear beam with turned end to a bending beam was investigated by applying different composite strips. Therefore various arising in each of strength, ductility, rigidity, and energy dissipation capacity were obtained. A total of 12 small-scaled experimental programs have been performed. Beam dimensions have been taken as 100×150×1000 mm. Four beams have been tested as unstrengthened samples. This paper focuses on the effect of minimum CFRP and GFRP strip width on behaviours of RC beams shear-strengthened with full-wrapping, U-wrapping, and U-wrapping+longitudinal bonding strips. Strengthened beams showed significant increments for flexural ductility, energy dissipation, and inelastic performance. The full wrapping strips applied against shear failure have increased the load-carrying capacity of samples 53%-63% interval rate. Although full wrapping is the best strengthening choice, the U-wrapping and U-wrapping+longitudinal strips of both CFRP and GFRP bonding increased the shear capacity by 53%~75% compared to the S2 sample. In terms of ductility, the best result has been obtained by the type of strengthening where the S5 beam was completely GFRP wrapped. The experimental results were also compared with the analytically given by ACI440.2R-17, TBEC-2019 and FIB-2001. Especially in U-wrapped beams, the estimation of FIB was determined to be 81%. The estimates of the other codes are far from meeting the experimental results; therefore, essential improvements should be applied to the codes, especially regarding CFRP and GFRP deformation and approaches for longitudinal strip connections. According to the test results, it is suggested that GFRP, which is at least as effective but cheaper than CFRP, may be preferred for strengthening applications.

Experimental and numerical study of Persian brick masonry barrel vaults under probable structural hazards

  • Saeid Sinaei;Esmaeel Izadi Zaman Abadi;Seyed Jalil Hoseini
    • Structural Engineering and Mechanics
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    • 제87권4호
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    • pp.317-332
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    • 2023
  • Understanding and analysing the behaviour and response of historical structures in the face of climate changes and environmental conditions is of utmost significance for their preservation. There are several structural hazards associated with climate and hydrology changes in the region, including the settlement of piers, the rotation of piers, and temperature changes. The present study investigates the experimental and numerical structural behaviour of skewed and non-skewed Persian brick masonry barrel vaults under various conditions. The external loading conditions included pier rotation in five modes, settlement, and temperature variations in four states. Initially, the experiments extracted the mechanical properties of the scaled materials. Then, three semi-circular brick barrel vaults were tested with gravitational loads. The outcomes were used to develop and validate the finite element model. Following the development of the finite element model, numerical and parametric studies were conducted on the effect of the aforementioned structural hazards on the response of brick masonry barrel vaults with various Persian geometries (semi-circular, drop pointed, and four-centred), angles of skew (0, 15, 30, and 45 degrees), and dimensional ratios. According to the findings, the fragility of masonry materials makes historical structures susceptible to failure under different loading. A brick barrel vault fails in the presence of minor rotation and settlement of the piers. The four-centred geometric shape has the lowest performance among the seven Persian geometries; therefore, its health monitoring and retrofitting should be prioritised. In Isfahan, Iran, temperature variations, particularly during the warm seasons, cause critical conditions in such structures.

Antimutagenic Effects of Ginsenoside Rb$_1$, Rg$_1$ in the CHO-K1 Cells by Benzo[a]pyrene with Chromosomal Aberration Test and Comet Assay

  • Kim, Jong-Kyu;Kim, Soo-Jin;Rim, Kyung-Taek;Cho, Hae-Won;Kim, Hyeon-Yeong;Yang, Jeong-Sun
    • Molecular & Cellular Toxicology
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    • 제5권2호
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    • pp.126-132
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    • 2009
  • The usage and types of chemicals are advancing, specializing, large-scaled increasing, and new chemical exposed workers are concerning to occupational disease. The generation of reactive oxygen in the body from carcinogen, mutation and DNA damage in cancer is protected by natural antioxidants (phytochemicals) with antimutagenic effect. There were many reports of ginsenoside Rb$_1$, Rg$_1$ grievances of the genetic mutation to suppress the effect confirm the genetic toxicity test with chromosomal aberration test and the Comet (SCGE) assay confirmed the suppression effect occurring chromosomal DNA damage. We had wanted to evaluate the compatibility and sensitivity between the chromosomal aberration (CA) test and the Comet assay. We used the CA test and Comet assay to evaluate the anti-genotoxicity of ginsenoside Rb$_1$ and Rg$_1$, in CHO-K1 (Chinese hamster ovary fibroblast) cell in vitro, composed negative control (solvent), positive control (benzo[a]pyrene), test group (carcinogen+variety concentration of ginsenoside) group. The positive control was benzo[a]pyrene (50 $\mu$M), well-known carcinogen, and the negative control was the 1 % DMSO solvent. The test group was a variety concentration of ginsenoside Rb$_1$, Rg$_1$ with 10$^{-8}$%, 10$^{-6}$%, 10$^{-4}$%, 10$^{-2}$%, 1%, 10%. In chromo-somal aberration test, we measured the number of cells with abnormally structured chromosome. In Comet assay, the Olive tail moment (OTM) and Tail length (TL) values were measured. The ratio of cell proliferation was increased 8.3% in 10$^{-8}$%, 10$^{-6}$%, 10$^{-4}$%, 10$^{-2}$%, 1%, 10% Rb$_1$ treated groups, and increased 10.4% in 10$^{-10}$%, 10$^{-8}$%, 10$^{-6}$%, 10$^{-4}$%, 10$^{-2}$%, 1% Rg$_1$ treated groups. In the CA test, the number of chromosomal aberration was decreased all the Rb$_1$ and Rg$_1$ treated groups. In the Comet assay, the OTM values were decreased in all the Rb$_1$ and Rg$_1$ treated groups. To evaluate the compatibility between CA and Comet assay, we compared the reducing ratio of chromosomal abnormalities with its OTM values, it was identified the antimutagenicity of ginsenoside, but it was more sensitive the CA test than the Comet assay. Ginsenoside Rb$_1$ and Rg$_1$ significantly decrease the number of cells with chromosomal aberration, and decrease the extent of DNA migration. Therefore, ginsenoside Rb$_1$, Rg$_1$ are thought as an antioxidant phytochemicals to protect mutagenicity. The in vitro Comet assay seems to be less sensitive than the in vitro chromosomal aberration test.

사력댐 사석 보호공의 붕괴 지연 효과에 대한 실험 연구 (Experimental Study of Collapse Delay Effect of Riprap on Dam Slope)

  • 정석일;김승욱;김홍택;이승오
    • 한국방재안전학회논문집
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    • 제11권1호
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    • pp.31-38
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    • 2018
  • 국내 중소규모 저수지의 99.1%는 흙댐으로, 건설비용이 저렴하여 용이한 시공성을 갖고 있다. 그러나 흙댐은 월류에 취약하기 때문에, 홍수 시 급격한 붕괴 가능성이 있다. 이러한 붕괴가 발생할 경우 급격한 홍수량 증가로 이어지기 때문에, 하류 치수 안전성이 위협 받을 가능성이 크다. 이에 본 연구에서는 흙댐 사면에 포설한 사석의 붕괴 지연효과를 실험을 통해 검토하였다. 실험은 사각단면의 직선형 개수로에서 수행하였으며, 보호공 사석의 크기를 3가지로 결정하였다. 선행 연구들과 차이점은 부정류로 실험을 수행한 것이며, 대상은 일반적인 형태의 가물막이로 결정하였다. 실험결과 차원해석 및 선행연구를 이용하여 서석보호공이 포설된 흙댐 붕괴 시간에 대한 새로운 공식을 제시하였다. 또한 사석 보호공이 설치된 경우 실험을 통해 붕괴 지연효과에 대해 검토한 결과 포설된 사석의 2배 이상의 효과가 있는 것으로 확인되었다. 본 연구 결과는 EAP (Emergency Aciton Plan) 수립 및 제방 설계와 같은 하천 계획에 도움이 될 것으로 판단된다.

제주 거문오름 용암동굴계의 진동영향에 관한 실험적 연구 (Experimental Study of the Effect of Vibration on the Geomunoreum Lava Tube System in Jeju)

  • 송재용;이근춘;안웅산;임현묵;서용석
    • 지질공학
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    • 제30권3호
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    • pp.327-345
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    • 2020
  • 본 연구는 제주도에서 각종 개발과정 중 발생되는 지반진동이 용암동굴에 미치는 영향에 대해 분석하고, 용암동굴의 효율적인 관리보존 대책을 마련하기 위해 수행되었다. 이를 위해 제주도 거문오름동굴계분포지역에서 암질별 RMR과 Q-system 암반분류를 통해 지반상태를 평가하였고, 시추공 내에서 발파를 수행하여 만장굴 및 용천동굴에서 진동속도를 측정하였다. 암반분류 결과와 진동속도를 분석한 결과 암질이 좋을수록 진동의 영향이 크고, 암질이 불량할수록 진동영향이 작게 나타나는 경향을 보였으나 지반불균질성 등의 이유로 선형관계가 뚜렷하게 나타나진 않았다. 진동시험 결과를 토대로 진동속도(PPV)와 진동레벨(dB(V))의 상관관계식을 도출하였으며, 생활진동규제기준(진동레벨 주간 65 dB(V), 야간 60 dB(V))을 만족하려면 진동속도가 주간 0.371 cm/s, 야간 0.285 cm/s인 것으로 계산된다. 야간 진동기준이 더 보수적인 값이므로 허용진동기준은 0.285 cm/s 이하로 설정될 필요가 있다. 연구지역에서의 발파진동추정식 결정을 위하여 자승근 환산거리 및 삼승근 환산거리에 대해 선형 회귀분석을 수행한 결과, 결정계수(R2)가 0.76 이상으로 나타나 양호한 신뢰성을 가지는 것으로 평가되었다. 도출된 발파진동추정식의 자승근 관계식을 적용하여 문화재 진동기준치인 0.2 cm/s를 만족하는 장약량을 산정하였고, 동굴에서 50 m 이격된 경우 2.88 kg, 100 m 이격된 경우 11.52 kg으로 계산되었다.

수직축 조류발전 터빈의 유체공학적 용량 산정기법 개발 (Development of Hydrodynamic Capacity Evaluation Method for a Vertical-Axis Tidal Stream Turbine)

  • 이대형;현범수;이정기;김문찬;이신형
    • 한국해양환경ㆍ에너지학회지
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    • 제15권2호
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    • pp.142-149
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    • 2012
  • 다양한 축척을 갖는 조류발전용 수직축 터빈의 유속과 직경의 변화가 터빈의 유체공학적 효율에 미치는 영향을 수치적으로 연구하였다. 수치해석은 직경 산정식을 사용하여 도출된 동일형상의 다양한 치수의 기준터빈에 대하여 수행되었으며 유속과 직경 변화에 따른 효율의 차이에 대해 알아보았다. 해석결과 터빈의 효율은 레이놀즈 수 변화에 따라 체계적으로 증가하는 것을 확인하였으며, 이로부터 크기가 다른 동일형상의 터빈의 성능은 TSR(Tip Speed Ratio)과 레이놀즈수(Reynolds number)만의 함수로 표시할 수 있음을 알 수 있었다. 이상의 수치해석 결과를 이용하여 수직축 터빈 초기설계단계에서 필요한 간편한 용량산정기법을 제안하고 유속, 직경, 터빈회전수 간의 상호관계를 다양한 관점에서 도표화 하였다. 본 연구는 터빈용량 10 kW~300 kW 사이의 수직축 터빈 초기설계 시에 효과적으로 활용될 수 있을 것으로 기대된다.

Low-VHF 대역 방향탐지용 소형 안테나의 탱크 장착 위치에 따른 방사특성 연구 (A Study on Radiation Char acter istics of Electr ically Small Antenna for Low-VHF Band Direction Finding according to Tank Mounting Position)

  • 문상만;우종명
    • 한국인터넷방송통신학회논문지
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    • 제14권2호
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    • pp.127-134
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    • 2014
  • 본 논문은 방향탐지용 Low-VHF 대역 소형 안테나의 탱크 장착 위치에 따른 방사특성에 관한 연구이다. 먼저, 안테나를 평면 접지면상 장착시, 다음으로 탱크 위 장착시 방사특성에 대하여 각각 시뮬레이션(40MHz)과 1/10 축소된 모델에 대하여 제작 측정(400MHz)으로 확인하였다. 평면 접지면상 장착시 급전점이 ${\phi}=0^{\circ}$, $180^{\circ}$(xz-면)에 위치할 경우, yz-면 성분(H-면)과 xz-면 $E_{\theta}$ 성분(E-면) 방사패턴이 좁은 접지면의 영향으로 상반구상 무지향성 방사 특성을 유지함을 확인 하였다. 다음으로 탱크 장착시에도 평면 접지면상 장착시 방사특성과 동일하게 상반구상에서 yz-면 $E_{\phi}$ 성분(H-면)과 xz-면 $E_{\theta}$ 성분(E-면) 방사패턴 모두 장착위치에 거의 영향이 없는 상반구상 무지향성 방사 특성을 나타내었다. 이로써, 제안된 방향탐지용 소형 안테나를 탱크에 장착 할 경우, 급전점을 접지면이 좁은 xz-면(E-면)에 위치시킨다면, 방향탐지용 안테나로써 보다 안정적인 방사특성을 유지함을 확인 할 수 있었다.

일부 직장근로자들의 구강건강에 대한 인지도 및 실천도에 관한 연구 (Research into Some Company Workers' Awareness of the Hygiene of the Mouth and their Practice of It)

  • 정정옥;배수명;송귀숙
    • 치위생과학회지
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    • 제8권1호
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    • pp.21-27
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    • 2008
  • 본 연구는 직장근로자들의 구강건강증진방안을 마련하는 연구의 일환으로 직장근로자들을 대상으로 구강건강 인지도와 실천도를 파악하여 적절한 산업구강보건정책 수립과 직장 구강보건 교육프로그램을 개발하는데 필요한 기초자료를 제공하고자 본 연구를 시행하였다.본 연구의 결론은 다음과 같다.첫째, 구강건강인지도에서는 잇솔질에 의한 치주질환예방효과에 대한 인지도는 높았지만, 충치예방효과에 대해서는 인지도가 낮게 나타났고, 구강위생용품의 필요성에 대한 인지도는 낮은 점수를 보였다. 둘째, 구강건강 실천도에서는 스켈링에 대한 필요성 및 중요성에 대한 인지도는 낮게 나타났으며, 대부분 스켈링을 정기적으로 받지 않은 것으로 나타났고, 구강건강을 위해 정기적인 구강검진이 필요하다고 높게 인식하고 있었지만 실천에서는 낮은 점수를 보였다.셋째, 조사대상자의 일반적 특성에 따른 구강건강인지도를 보면, 결혼여부에서는 기혼이 미혼에 비해 구강건강인지도가 높게 나타났고, 구강건강에 대한 관심도에서는 구강건강에 대한 관심이 높을수록 구강건강인지도가 높은 것으로 나타났다.넷째, 구강건강 실천도에서는 한 달 평균 수입이 높을수록 구강건강실천도가 높게 나타났으며, 자신의 구강건강상태에서는 구강건강상태가 좋지 않을수록 구강건강실천도가 높게 나타났다. 이상의 결과에서 근로자들은 생활의 대부분을 직장에서 보내게 되므로 직장에서의 구강건강행태를 파악하고 그에 따른 적절한 구강건강교육을 시행하는 것이 필수적인 일이라 여겨진다. 또한 구강건강을 유지할 수 있는 프로그램을 지속적으로 개발하여 효과적으로 운용한다면 구강건강이 크게 증진되리라 사료된다.

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Applications of XPS and SIMS for the development of Si quantum dot solar cell

  • 김경중;홍승휘;김용성;이우;김영헌;서세영;장종식;신동희;최석호
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2010년도 제39회 하계학술대회 초록집
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    • pp.297-297
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    • 2010
  • Precise control of the position and density of doping elements at the nanoscale is becoming a central issue for realizing state-of-the-art silicon-based optoelectronic devices. As dimensions are scaled down to take benefits from the quantum confinement effect, however, the presence of interfaces and the nature of materials adjacent to silicon turn out to be important and govern the physical properties. Utilization of visible light is a promising method to overcome the efficiency limit of the crystalline Si solar cells. Si quantum dots (QDs) have been proposed as an emission source of visible light, which is based on the quantum confinement effect. Light emission in the visible wavelength has been reported by controlling the size and density of Si QDs embedded within various types of insulating matrix. For the realization of all-Si QD solar cells with homojunctions, it is prerequisite not only to optimize the impurity doping for both p- and n-type Si QDs, but also to construct p-n homojunctions between them. In this study, XPS and SIMS were used for the development of p-type and n-type Si quantum dot solar cells. The stoichiometry of SiOx layers were controlled by in-situ XPS analysis and the concentration of B and P by SIMS for the activated doping in Si nano structures. Especially, it has been experimentally evidenced that boron atoms in silicon nanostructures confined in SiO2 matrix can segregate into the Si/$SiO_2$ interfaces and the Si bulk forming a distinct bimodal spatial distribution. By performing quantitative analysis and theoretical modelling, it has been found that boron incorporated into the four-fold Si crystal lattice can have electrical activity. Based on these findings, p-type Si quantum dot solar cell with the energy-conversion efficiency of 10.2% was realized from a [B-doped $SiO_{1.2}$(2 nm)/$SiO_2(2\;nm)]^{25}$ superlattice film with a B doping level of $4.0{\times}10^{20}\;atoms/cm^2$.

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