• Title, Summary, Keyword: neutral axis

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Exact poisson distribution in the use of NPB with aiming errors

  • Kim, Joo-Hwan
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • pp.967-973
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    • 1995
  • A neutral particle beam(NPB) aimed at the object and receive a small number of neutron signals at the detector to estimate the mass of an object Since there is uncertainty about the location of the axis of the beam relative to the object, we could have aiming errors which may lead to incorrect information about the object. Under the two assumptions that neutral particle scattering distribution and aiming errors have a circular normal distribution respectively, we have derived an exact probability distribution of neutral particles. It becomes a Poison-power function distribution., We proved monotone likelihood ratio property of tlis distribution. This property can be used to find a criteria for the hypothesis testing problem.

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Seismic Consideration of Reinforced Concrete Wall Section

  • Kim, Jang-Hoon
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.210-215
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    • 2003
  • Seismic capacity of reinforced concrete bearing wall subjected to high axial loading and moment can be attained by improving the deformability of compression zone or by reducing the neutral axis depth. For this two existing options for ductility enhancement were reviewed and improved to conveniently apply to the seismic improvement of compression zone of the wall: (1) end confinement of concrete due to transverse steel and (2) boundary element.

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A Study on the Flexural Behavior according to Filling conditions of Beams Members(A Siries) Using High Performance Concrete (고유동성 콘크리트를 이용한 보부재(A시리즈)의 충전상황별 휨거동 연구)

  • 장일영;윤영수;엄주환;송재호
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.306-311
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    • 1996
  • This paper persents the flexural behavior of high performance concrete beams having different concrete filling conditions. Three tests were conducted on full-scale beam specimens with design concrete compressive strength of 400 kg/$\textrm{cm}^2$. Different concrete filling conditions were intentionally made such that the first beam specimen was soundly cast to obtain the perfect concrete filling condition. Second beam specimen was cast in such a way that up to the longitudinal tensile reinforcement from the top, good concrete was filled while poor concrete was poured for the bottom part to simulate the poor workamanship, workability and unsatisfactory compaction. Third beam specimens was cast in such a way that up to the neutral axis of the beam section from the top, good concrete was filled while so did for the bottom part as the second beam specimen. The test results were analyzed in terms of load-displacement response, formation of crack, crack width, crack spacing and shift of neutral axis. An evaluation of the ductile response fo three different beam specimens was made in combination with the ultimate load accoding to the three different concrete filling conditions.

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Evaluation of Structural Performance of RC T-shaped Walls with Different ratios of axial load and vertical reinforcement (압축력비와 수직철근비에 따른 RC T형 벽체의 구조성능 평가에 관한 해석적 연구)

  • 하상수;최창식;이리형
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.403-408
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    • 2003
  • The objective of this study is to understand the variables affected the confinement for the transverse reinforcement of the reinforced concrete structural walls with the T-shaped cross section subjected to cyclic lateral loads. The structural performance of T-shaped walls was advanced by the transverse reinforcement which restrained the concrete subjected to compressive stress. If the arrangement of transverse reinforcement was not suitable for the confinement, T-shaped walls happened the brittle failure by web crushing or bucking of vertical reinforcement at the compression zone. It is necessary to confine transverse reinforcement in order to prevent the these failure. But the location of neutral axis and the magnitude of ultimate strain vary according to the section shape, a ratio of axial load, a ratio of wall cross sectional area to the floor-plan area, an aspect ratio and the reinforcement ratio. Therefore, the objective of this research is to grasp the location of neutral axis and the range which needs for the confinement of transverse reinforcement through the results of the sectional analysis which varies the ratio of axial load and the ratio of vertical reinforcement.

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Prediction of Deflection of Reinforced Concrete Beams due to Creep (크리프에 의한 철근콘크리트 보의 처짐 예측)

  • 이상순;김용빈;김진근;이수곤
    • Magazine of the Korea Concrete Institute
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    • v.10 no.6
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    • pp.253-260
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    • 1998
  • An approximate method for the calculation of creep deflections of reinforced concrete beams under sustained service loads is proposed. The position of neutral axis and strain and stress distribution of fully cracked section after creep is determined from the requirements of strain compatibility and equilibruim of a section and then the long-term flexural rigidity of fully cracked section is determined based on the new neutral axis. The long-term flexural rigidity of uncracked section at the level of the reinforcenment. The approach of calculating long-term effective flexural rigidity and defections is similar to the current American Concrete Institue procedure for calculating effecitve moment of inertia and short-term deflections. The accuracy of the analysis is verified by comparison with several experimental mesurements of beam deflectons. The result is good between the theotetical values and mesured valus.

Development of Long-Span Steel-Precast Composite Beam for Green Apartment Building (장스팬이 가능한 친환경 공동주택용 철골 프리캐스트 합성보 개발)

  • Yoon, Tae-Ho;Hong, Won-Kee;Park, Seon-Chee;Yune, Dai-Young
    • KIEAE Journal
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    • v.11 no.1
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    • pp.9-14
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    • 2011
  • Currently, the multi-residential apartments used in Korea are mostly bearing wall apartments which don't satisfy consumers for the lack of architectural plan flexibility. And due to remodelling-incompatible, bearing wall apartments have to be reconstructed. It is, thus, necessary to develop multi-residential apartments utilizing composite beam that can replace the conventional bearing wall-type apartment buildings. Composite beams proposed in this paper ensure modification of space and quality control, while the floor heights are maintained at the same floor height as in bearing wall structures. This study analyzes the experimental behavior of composite beams with proper combination of structural steel, reinforced concrete, and precast concrete. By comparing with the theoretical analysis and experimental results, the accuracy of flexural moment capacity and neutral axis was evaluated. The experiments were performed by two simply-supported specimens using loading and unloading. When the analysis results were compared with the experimental results, the flexural moment capacity of the composite beam was shown with an error of approximately -0.5 to 0.1% at the maximum load limit state.

Evaluation on structural behaviors of prestressed composite beams using external prestressing member

  • Ahn, Jin-Hee;Jung, Chi-Young;Kim, Sang-Hyo
    • Structural Engineering and Mechanics
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    • v.34 no.2
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    • pp.247-275
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    • 2010
  • In this study, experimental, numerical, and analytical approaches were carried out to evaluate the behavior and prestressing effect of prestressed composite beam by external tendon and cover plate. Behavior of prestressed composite beam, load-carrying capacity, effects of prestressing, and ultimate strength were estimated. The contribution of the section increase of the prestressing method using tendon was less than the prestressing method using cover plate. In accordance with numerical and analytical approaches, the ultimate strength of the prestressed composite beam is shown to be the same value because strength is determined according to the plastic resistance moment and the plastic neutral axis; however, both plastic resistance moment and neutral axis are not affected by prestressing force but affected by sectional stiffness of the prestressing member. Based on these approaches, we concluded that the prestressing method using tendon can be useful in applications without an increase in self-weight, and the prestressing method using high-strength cover plate can be applied to reduce the deflection of the composite beam. The prestressing method using high-strength cover plate can also be used to induce prestress of the composite beam in the case of a large deflection due to a smaller sectional stiffness of the composite beam.

Minimum deformability design of high-strength concrete beams in non-seismic regions

  • Ho, J.C.M.;Zhou, K.J.H.
    • Computers and Concrete
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    • v.8 no.4
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    • pp.445-463
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    • 2011
  • In the design of reinforced concrete (RC) beams, apart from providing adequate strength, it is also necessary to provide a minimum deformability even for beams not located in seismic regions. In most RC design codes, this is achieved by restricting the maximum tension steel ratio or neutral axis depth. However, this empirical deemed-to-satisfy method, which was developed based on beams made of normal-strength concrete (NSC) and normal-strength steel (NSS), would not provide a consistent deformability to beams made of high-strength concrete (HSC) and/or high-strength steel (HSS). More critically, HSC beams would have much lower deformability than that provided previously to NSC beams. To ensure that a consistent deformability is provided to all RC beams, it is proposed herein to set an absolute minimum rotation capacity to all RC beams in the design. Based on this requirement, the respective maximum limits of tension steel ratio and neutral axis depth for different concrete and steel yield strengths are derived based on a formula developed by the authors. Finally for incorporation into design codes, simplified guidelines for designing RC beams having the proposed minimum deformability are developed.

Experimental study on creep behavior of fly ash concrete filled steel tube circular arches

  • Yan, Wu T.;Han, Bing;Zhang, Jin Q.;Xie, Hui B.;Zhu, Li;Xue, Zhong J.
    • Steel and Composite Structures
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    • v.27 no.2
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    • pp.185-192
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    • 2018
  • Fly ash can significantly improve concrete workability and performance, and recycling fly ash in concrete can contribute to a cleaner environment. Since fly ash influences pozzolanic reactions in concrete, mechanical behaviors of concrete containing fly ash differ from traditional concrete. Creep behaviors of fly ash concrete filled steel tube arch were experimentally investigated for 10% and 30% fly ash replacement. The axes of two arches are designed as circular arc with 2.1 m computed span, 0.24 m arch rise, and their cross-sections are all in circular section. Time dependent deflection and strain of loading and mid-span steel tube were measured, and long term deflection of the model arch with 10% fly ash replacement was significantly larger than with 30% replacement. Considering the steel tube strain, compressive zone height, cross section curvature, and internal force borne by the steel tube, the compressive zone height and structural internal forces increased gradually over time due to concrete creep. Increased fly ash content resulted in more significant neutral axis shift. Mechanisms for internal force effects on neutral axis height were analyzed and verified experimentally.

IPMSM Design for Sensorless Control Considering Magnetic Neutral Point Shift According to Magnetic Saturation

  • Choi, JaeWan;Seol, Hyun-Soo;Lee, Ju
    • Journal of Electrical Engineering and Technology
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    • v.13 no.2
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    • pp.752-760
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    • 2018
  • In this paper, interior permanent magnet synchronous motor (IPMSM) design for sensorless drive, considering magnetic neutral point shift according to magnetic saturation, has been proposed. Sensorless control was divided into a method based on inductance and a method based on back induced voltage. Because induced voltage is very small at zero or low speed, error in rotor initial position estimation may occur. Using the ratio of saliency addresses this problem. When using high-frequency injections at low speed, the rotor's initial position is estimated at the smallest portion of the inductance. IPMSM has the minimum inductance at the d-axis. However, if magnetic saturation leads to magnetic neutral point variation, following the load current change, there is a change in the minimum point of inductance. In this case, it can lead to failure of initial rotor position estimation. As a result, it is essential that the blocking design has an inductance minimum point shift. As such, in this study, an IPMSM design method, by blocking magnetic neutral point change, has been proposed. After determining the inductance profile based on the finite element analysis (FEA), the results of proposed method were verified.