• 제목/요약/키워드: Ratio analysis

검색결과 21,676건 처리시간 0.049초

Development of Modified Flexibility Ratio - Racking Ratio Relationship of Box Tunnels Subjected to Earthquake Loading Considering Rocking

  • Duhee Park;Van-Quang Nguyen;Gyuphil Lee;Youngsuk Lee
    • 한국지반환경공학회 논문집
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    • 제24권2호
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    • pp.13-24
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    • 2023
  • Tunnels may undergo a larger or a smaller response compared with the free-field soil. In the pseudo-static procedure, the response of the tunnel is most often characterized by a curve that relates the racking ratio (R) with the flexibility ratio (F), where R represents the ratio of the tunnel response with respect to the free-field vibration and F is the relative stiffness of the tunnel and the surrounding soil. A set of analytical and empirical curves that do not account for the depth and the aspect ratio of the tunnel are typically used in practice. In this study, a series of dynamic analyses are conducted to develop a set of F-Rm relations for use in a frame analysis method. Rm is defined as an adjusted R where the rocking mode of deformation is removed and only the racking deformation is extracted. The numerical model is validated against centrifuge test recordings. The influence of aspect ratio, buried depth of tunnel on results is investigated. The results show that Rm increases with the increase of the buried depth and the aspect ratio. The widely used F-R relations are highlighted to be different compared with the obtained results in this study. Therefore, the updated F-Rm relations with proposed equations are recommended to be used in practice design. The rocking response decreases with either the decrease of the difference of stiffness between surrounding soil and tunnel or the larger aspect ratio of the tunnel section.

Comparative analysis of damping ratio determination methods based on dynamic triaxial tests

  • Song Dongsong;Liu Hongshuai
    • Earthquakes and Structures
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    • 제25권4호
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    • pp.249-267
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    • 2023
  • Various methods for determining the damping ratio have been proposed by scholars both domestically and abroad. However, no comparative analysis of different determination methods has been seen yet. In this study, typical sand (Fujian standard sand) and cohesive soils were selected as experimental objects, and undrained strain-controlled dynamic triaxial tests were conducted. The differences between existing damping ratio determination methods were theoretically compared and analyzed. The results showed that the hysteresis curve of cohesive soils had better symmetry and more closely conformed to the definition of equivalent linear viscoelasticity. For non-cohesive soils, the differences in damping ratio determined by six methods were significant. The differences decreased with increasing confining pressure and relative density, but increased gradually with increasing shear strain, especially at high shear strains, where the maximum relative error reached 200%. For cohesive soils, the differences in damping ratio determined by six methods were relatively small, with a maximum relative error of about 50%. Moreover, they were less affected by effective confining pressure and had the same changing trend under different effective confining pressures. The damping ratio determination method has a large effect on the seismic response of soils distributed by non-cohesive soils, with a maximum relative error of about 15% for the PGA and up to about 30% for the Sa. However, for soil layers distributed by cohesive soils, the damping ratio determination method has less influence on the seismic response. Therefore, it is necessary to adopt a unified damping ratio determination method for non-cohesive soils, which can effectively avoid artificial errors caused by different determination methods.

비부착 긴장재의 응력 변화에 영향을 미치는 변수에 관한 고찰 (Parametric study for influential factors on unbonded tendon stress increase)

  • 이선화;문정호;임재형
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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    • pp.651-656
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    • 2000
  • The strain compatibility analysis shows that the influential parameters of loading type, reinforcing ratio, and span-depth ratio affect on the tendon stress in unbonded prestresses concrete member significantly. However, existing test results did not comply exactly with the analytical results. In consequence, the present study was planned to examine the parameters in order to complete Moon/Lim's design equation. The test variables with 12 specimens were loading type, reinforcing ratio, and span-depth ratio. As results, the effect of influential parameters were examined throughly and Moon/Lim's design equation was proven to be accurate.

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서남권 도서지역에 적합한 1kW급 수평축 풍력터빈 로터 블레이드 설계 및 유동해석 (Design and Flow Analysis on the 1kW Class Horizontal Axis Wind Turbine Rotor Blade for Use in Southwest Islands Region)

  • 이준용;최낙준;윤한용;최영도
    • 한국유체기계학회 논문집
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    • 제15권3호
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    • pp.5-11
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    • 2012
  • This study is to develop a 1kW-class horizontal axis wind turbine(HAWT) rotor blade which will be applicable to relatively low wind speed regions in southwest islands in Korea. Shape design of 1kW-class small wind turbine rotor blade is carried out using a blade profile with relatively high lift to drag ratio by blade element momentum theory(BEMT). Aerodynamic analysis on the newly designed rotor blade is performed with the variation of tip speed ratio. Power coefficient and pressure coefficient of the designed rotor blade are investigated according to tip speed ratio.

Performance Analysis of an Aircraft Gas Turbine Engine using Particle Swarm Optimization

  • Choi, Jae Won;Sung, Hong-Gye
    • International Journal of Aeronautical and Space Sciences
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    • 제15권4호
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    • pp.434-443
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    • 2014
  • A turbo fan engine performance analysis and the optimization using particle swarm optimization(PSO) algorithm have been conducted to investigate the effects of major performance design parameters of an aircraft gas turbine engine. The FJ44-2C turbofan engine, which is widely used in the small business jet, CJ2 has been selected as the basic model. The design parameters consists of the bypass ratio, burner exit temperature, HP compressor ratio, fan inlet mass flow, and nozzle cooling air ratio. The sensitivity analysis of the parameters has been evaluated and the optimization of the parameters has been performed to achieve high net thrust or low specific fuel consumption.

An efficient and simple four variable refined plate theory for buckling analysis of functionally graded plates

  • Bellifa, Hichem;Bakora, Ahmed;Tounsi, Abdelouahed;Bousahla, Abdelmoumen Anis;Mahmoud, S.R.
    • Steel and Composite Structures
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    • 제25권3호
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    • pp.257-270
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    • 2017
  • In this article, an efficient and simple refined theory is proposed for buckling analysis of functionally graded plates by using a new displacement field which includes undetermined integral variables. This theory contains only four unknowns, with is even less than the first shear deformation theory (FSDT). Governing equations are obtained from the principle of virtual works. The closed-form solutions of rectangular plates are determined. Comparison studies are carried out to check the validity of obtained results. The influences of loading conditions and variations of power of functionally graded material, modulus ratio, aspect ratio, and thickness ratio on the critical buckling load of functionally graded plates are examined and discussed.

태양열 집열면이 있는 4각 덕트 내의 열전달 특성에 관한 연구 (A Study on the Characteristics of Heat Transfer in Quadrangle Duct with Solar Absorber Plate)

  • 고동국;조대진;윤석주;박상규
    • 설비공학논문집
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    • 제14권12호
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    • pp.1014-1022
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    • 2002
  • This paper analyzed the characteristics of heat transfer in quadangle duct with absorber plate by solar radiation. Effects o( Reynolds number on increasing temperature at outlet for variation of absorber plate temperature were analyzed by using numerical analysis technique. And also the effects of turbulent intensity of inlet flow on increasing temperature at outlet for various duct height and effects of inlet aspect ratio of quadrangle duct and position of heating surface on the outlet temperature were analysed. As the results, Outlet temperature was greatly influenced in low Reynolds number. And the highest outlet temperature distribution appeared on the inlet aspect ratio 2 because of the buoyancy effect.

외연적 유한요소법을 이용한 세장비가 큰 타원형 컵 성형공정의 다단계 해석 (Multi-stage Analysis of Elliptic Cup Drawing Processes with the Large Aspect Ratio by an Explicit Elasto-Plastic Finite Element Method)

  • 김세호;김승호;허훈
    • 소성∙가공
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    • 제9권3호
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    • pp.313-319
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    • 2000
  • Finite element analysis is carried out for simulation of the multi-stage elliptic cup drawing process with the large aspect ratio. The analysis incorporates with shell elements for an elasto-plastic finite element method with the explicit time integration scheme. For the simulation, LS-DYNA3D is utilized for its wide capability of solving forming problems. The simulation result shows that the non-uniform drawing ratio at the elliptic cross section ad the small shoulder radius cause failure such as tearing and wrinkling. The result suggests the guideline to modify the tool shape for prevention of the failure during the drawing process.

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혼합정수계획 모형을 활용한 원양산업의 최적 감척 일정계획 수립에 관한 연구 (A Study on Scheduling of Scrap Disposal for Deap-sea Fishing Industry Using a Mixed Integer Programming Model)

  • 김재희
    • 경영과학
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    • 제27권2호
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    • pp.55-66
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    • 2010
  • In Korea, deap-sea fishing industry plays an important role in a food industry. However, it is in a difficult situation because of the more competitive business environment. Therefore, there is a need to restructure the deap-sea fishing industry by scraping superannuated ships. This paper is designed to present scrap programs for deap-sea fishing industry of Korea. We performed ratio analysis to evaluate financial performance of fishing companies and then applied a mixed integer programming (MIP) model to identify optimal schedule for scraping. The results of the financial ratio analysis indicates that it is legible to provide governmental aid to Atlantic trawl, Northern Pacific trawl, and Indian ocean trawl with minimum required rate of return (MRR) of 3%, and the Atlantic strip fishing industry is qualified to receive the governmental aid with MRR value of 5%. Furthermore, by applying the MIP model to develop scrap planning, we demonstrate how our model can be used to restructure the deap-sea fishing industry of Korea.

점용접된 두 사각평판의 형상비 및 용접점수에 대한 전단좌굴하중의 유한요소해석 (Finite Element Analysis of the Shear Buckling Load with Respect to the Aspect Ratio and Number of Spots of two Rectangular Plates Spot-welded)

  • 한근조;전형용;이현철
    • 한국자동차공학회논문집
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    • 제8권6호
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    • pp.173-181
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    • 2000
  • The stability of a structural plate is a crucial problem which causes wrinkling and buckling. In this paper, the effect of the pattern of spot-welding points in the two rectangular plate on the shear buckling load is studied with respect to the thickness, the aspect ratio of plates, the number of welding spots. Buckling coefficient of the simple plate was compared with that of two plates with various conditions to extract the effect of buckling strength. The effect of the number of welding spots are studied in two directions, longitudinal and transverse directions. The concluded that the reinforcement effect was maximized when the aspect ratio was close to 1.5 and that the effect of number of welding spots in longitudinal direction was larger than that in transverse direction.

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