• 제목/요약/키워드: the base

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부양형 팽이기초의 하중전달 메커니즘에 따른 거동 (Behavior of Floating Base Plate by Stress Delivery Mechanism)

  • 정진혁;정효권;이송
    • 한국구조물진단유지관리공학회 논문집
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    • 제14권2호
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    • pp.137-144
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    • 2010
  • 팽이기초에 대한 일본과 국내에서 현재까지 공통적으로 연구되고 있는 것은 팽이기초의 현장재하실험에 대한 지지력과 침하량에 주목되어 있다. 그러나 팽이기초에서 선행되어야할 연구는 공법 자체가 상재하중을 하부에 어떠한 원리로 전달되는 지에 대한 분석이 수행되어야 한다. 이에 본 연구에서는 일본에서 개발된 Top-Base Foundation과 국내에서 개발된 부양형 팽이기초의 응력전달 메커니즘을 수치해석 및 실내모형실험을 통하여 분석하였다. 팽이기초의 하중전달 메커니즘을 분석한 결과 상재하중에 대한 팽이기초 자체의 하중저감 분담률은 주로 팽이기초와 쇄석사이에서 발생하는 주면마찰력이 가장 크게 나타났다. 또한, 팽이기초의 내부응력분산효과를 포함한 Top-Base Foundation의 총 응력분산각은 $41.8^{\circ}$이며, 부양형 팽이기초의 총 응력분산각은 $44.5^{\circ}$로 산정되었다.

위치결정 스테이지 베이스 진동 모델링 및 저감기법 개발 (Modeling and Countermeasure for Positioning Stage Base Vibration)

  • 박아영;임재곤;홍성욱
    • 한국생산제조학회지
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    • 제19권4호
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    • pp.476-484
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    • 2010
  • Precise positioning stages are often employed for precise machinery. For the purpose of vibration isolation, these precise positioning stages are mounted on a heavy base structure which is supported by compliant springs. Then the base structure is subjected to residual vibration due to the reactive force and vertical moving load induced by the stage motion. This paper investigates the vibration behavior of a positioning stage base and the associated vibration suppression technique. A dynamic model is developed to investigate the base vibration due to the reactive force and moving load effects by the moving stage. An input shaping technique is also developed to suppress the residual vibrations in base structures. Simulations and experiments show that the developed dynamic model adequately represents the base vibration and that the proposed input shaping technique effectively removes the residual vibrations from the positioning stage base.

외부연소를 고려한 기저유동 (Base Flow with External Combustion)

  • 신재렬;최정열
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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    • pp.92-97
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    • 2007
  • Numerical simulations were carried out to investigate the base drag characteristics of a base bleed projectile with a central propulsive jet by considering the base burning process. Overall fluid dynamic process is modeled by Navier-Stokes equations for reacting flows with two-equation $k-{\omega}$ SST turbulence closure. The combustion process is modeled by finite-rate chemistry with a given partially burned exit condition of the BBU (base-bleed unit). Besides the demonstrating the capability of the present CFD solver for the base drag and the interaction of the base flow with a rocket plume, present study gives an insight into the fluid dynamics and the combustion process of the hybrid-propulsion projectile.

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Seismic responses of base-isolated nuclear power plant structures considering spatially varying ground motions

  • Sayed, Mohamed A.;Go, Sunghyuk;Cho, Sung Gook;Kim, Dookie
    • Structural Engineering and Mechanics
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    • 제54권1호
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    • pp.169-188
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    • 2015
  • This study presents the effects of the spatial variation of ground motions in a hard rock site on the seismic responses of a base-isolated nuclear power plant (BI-NPP). Three structural models were studied for the BI-NPP supported by different number of lead rubber bearing (LRB) base isolators with different base mat dimensions. The seismic responses of the BI-NPP were analyzed and investigated under the uniform and spatial varying excitation of El Centro ground motion. In addition, the rotational degrees of freedom (DOFs) of the base mat nodes were taken to consider the flexural behavior of the base mat on the seismic responses under both uniform and spatial varying excitation. Finally, the seismic response results for all the analysis cases of the BI-NPP were investigated in terms of the vibration periods and mode shapes, lateral displacements, and base shear forces. The analysis results indicate that: (1) considering the flexural behavior of the base mat has a negligible effect on the lateral displacements of base isolators regardless of the number of the isolators or the type of excitation used; (2) considering the spatial variation of ground motions has a substantial influence on the lateral displacements of base isolators and the NPP stick model; (3) the ground motion spatial variation effect is more prominent on lateral displacements than base shear forces, particularly with increasing numbers of base isolators and neglecting flexural behavior of the base mat.

Seismic performance of secondary systems housed in isolated and non-isolated building

  • Kumar, Pardeep;Petwal, Sandeep
    • Earthquakes and Structures
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    • 제16권4호
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    • pp.401-413
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    • 2019
  • The concept of base isolation for equipment is well known. Its application in buildings and structures is rather challenging. Introduction of horizontal flexibility at the base helps in proper energy dissipation at the base level thus reducing the seismic demand of the super structure to be considered during design. The present study shows the results of a series of numerical simulation studies on seismic responses of secondary system (SS) housed in non-isolated and base-isolated primary structures (PS) including equipment-structure interactions. For this study the primary structure consists of two similar single bay three-store reinforced cement concrete (RCC) Frame building, one non-isolated with conventional foundation and another base isolated with Lead plug bearings (LPB) constructed at IIT Guwahati, while the secondary system is modeled as a steel frame. Time period of the base isolated building is higher than the fixed building. Due to the presence of isolator, Acceleration response is significantly reduced in both (X and Y) direction of Building. It have been found that when compared to fixed base building, the base isolated building gives better performance in high seismic prone areas.

Flexural behavior of steel storage rack base-plate upright connections with concentric anchor bolts

  • Zhao, Xianzhong;Huang, Zhaoqi;Wang, Yue;Sivakumaran, Ken S.
    • Steel and Composite Structures
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    • 제33권3호
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    • pp.357-373
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    • 2019
  • Steel storage racks are slender structures whose overall behavior and the capacity depend largely on the flexural behavior of the base-plate to upright connections and on the behavior of beam-to-column connections. The base-plate upright connection assembly details, anchor bolt position in particular, associated with the high-rise steel storage racks differ from those of normal height steel storage racks. Since flexural behavior of high-rise rack base connection is hitherto unavailable, this investigation experimentally establishes the flexural behavior of base-plate upright connections of high-rise steel storage racks. This investigation used an enhanced test setup and considered nine groups of three identical tests to investigate the influence of factors such as axial load, base plate thickness, anchor bolt size, bracket length, and upright thickness. The test observations show that the base-plate assembly may significantly influence the overall behavior of such connections. A rigid plate analytical model and an elastic plate analytical model for the overall rotations stiffness of base-plate upright connections with concentric anchor bolts were constructed, and were found to give better predictions of the initial stiffness of such connections. Analytical model based parametric studies highlight and quantify the interplay of components and provide a means for efficient maximization of overall rotational stiffness of concentrically anchor bolted high-rise rack base-plate upright connections.

CFD를 이용한 초음속 유도탄 기저항력 예측 (BASE DRAG PREDICTION OF A SUPERSONIC MISSILE USING CFD)

  • 이복직
    • 한국전산유체공학회지
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    • 제11권3호
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    • pp.59-63
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    • 2006
  • Accurate prediction of a supersonic missile base drag continues to defy even well-rounded CFD codes. In an effort to address the accuracy and predictability of the base drags, the influence of grid system and competitive turbulence models on the base drag is analyzed. Characteristics of some turbulence models is reviewed through incompressible turbulent flow over a flat plate, and performance for the base drag prediction of several turbulence models such as Baldwin-Loman(B-L), Spalart-Allmaras(S-A), k-$\varepsilon$, k-$\omega$ model is assessed. When compressibility correction is injected into the S-A model, prediction accuracy of the base drag is enhanced. The NSWC wind tunnel test data are utilized for comparison of CFD and semi-empirical codes on the accuracy of base drag predictability: they are about equal, but CFD tends to perform better. It is also found that, as angle of attack of a missile with control fins increases, even the best CFD analysis tool we have lacks the accuracy needed for the base drag prediction.

Base Plate 연구를 통한 냉장고 진동 저감 방안 고찰 (A study on the Base Plate to reduce vibration for Refrigerator)

  • 김정선;;국정환;왕세명;이동현
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2007년도 춘계학술대회논문집
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    • pp.340-343
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    • 2007
  • In this paper, we present our method to reduce vibration of the base plate of a refrigerator by avoiding resonance between base plate and compressor operation. To verify the modes of the base plate, FE models of the base plate with free-free condition and applied boundary condition were built and validated by results from experimental modal analysis. Operating Deflection Shape analysis was applied to find the sensitive area on the base plate during compressor operation. In optimization process, Finite Difference Method - based sensitivity analysis is used to detect the most sensitive area. Finally, based on this numerical result, we will make beads on the base plate to reduce vibration of refrigerator.

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Modified complex mode superposition design response spectrum method and parameters optimization for linear seismic base-isolation structures

  • Huang, Dong-Mei;Ren, Wei-Xin;Mao, Yun
    • Earthquakes and Structures
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    • 제4권4호
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    • pp.341-363
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    • 2013
  • Earthquake response calculation, parametric analysis and seismic parameter optimization of base-isolated structures are some critical issues for seismic design of base-isolated structures. To calculate the earthquake responses for such non-symmetric and non-classical damping linear systems and to implement the earthquake resistant design codes, a modified complex mode superposition design response spectrum method is put forward. Furthermore, to do parameter optimization for base-isolation structures, a graphical approach is proposed by analyzing the relationship between the base shear ratio of a seismic base-isolation floor to non-seismic base-isolation one and frequency ratio-damping ratio, as well as the relationship between the seismic base-isolation floor displacement and frequency ratio-damping ratio. In addition, the influences of mode number and site classification on the seismic base-isolation structure and corresponding optimum parameters are investigated. It is demonstrated that the modified complex mode superposition design response spectrum method is more precise and more convenient to engineering applications for utilizing the damping reduction factors and the design response spectrum, and the proposed graphical approach for parameter optimization of seismic base-isolation structures is compendious and feasible.

미생물 유전체 프로젝트 수행을 위한 Base-Calling 오류 감지 프로그램 및 알고리즘 개발 (A Base-Calling Error Detection Program for Use in Microbial Genome Projects)

  • 이대상;박기정
    • 미생물학회지
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    • 제43권4호
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    • pp.317-320
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    • 2007
  • 미생물 유전체 프로젝트를 수행하는 과정에서 발생하는 base-calling 오류를 포함하는 것으로 의심되는 유전자나 염기서열의 리스트를 보여 주는 프로그램을 개발하였다. 이 프로그램의 모듈들은 base-calling 오류로 의심되는 염기들의 후보군을 유전체 프로젝트를 수행하는 주요 단계에서 감지할 수 있도록 하였다. 이들 프로그램들은 초기 단계에서는 Phrap 파일에 존재하는 contig assembly 정보를 이용하여 base-calling 오류를 감지하는 모듈, 중간 단계에서는 상동성 검색 결과물로부터 frame skift 돌연변이의 진위 유무를 분석할 수 있는 모듈, 마지막 단계에서는, 이미 발표된 미생물 유전체와 같은 종으로부터 유래된 균주에 대한 유전체 프로젝트를 수행할 경우, 비교유전체 분석 기법을 활용하여 base-calling 오류 가능성이 높은 서열의 후보군을 추출하여 해당서열의 크로마토그램파일을 유전체 연구자가 볼 수 있는 모듈로 구성되어 있다.