• Title, Summary, Keyword: 중립축

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Estimation of Plastic Bending Moment of Offshore Pipelines (해저관로의 대 변형 굽힘에 의한 소성 모멘트 추정)

  • Lee, Jong-Hyun;Choi, Han-Suk
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.20-25
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    • 2002
  • 본 논문은 대 변형 굽힘에 의한 소성 모멘트의 계산시 ovality를 고려한 파이프의 중립축에 대한 모멘트에 관해 논한다. 기존의 계산방법에 의한 중립축에 대한 모멘트 계산결과와 새로운 방법에 의한 계산결과를 비교해 보았다. 파이프가 길이방향의 모멘트에 의하여 굽어질 때, 증가하는 모멘트에 따른 ovality 변화를 고려하여 중립축에 대한 모멘트 계산에 적용해 보았다. 모멘트 계산은 타원형의 파이프 단면을 미세한 단면으로 나누어서 각 단면에 대한 응력을 비선형 strain-stress 식을 이용하여 구한 다음 중립축에 대해 계산을 수행하였다. 대 변형 굽힘에서 일어나는 실제현상 중 하나인 ovality를 파이프의 계산에 적용함으로써 좀 더 정확한 중립축에 대한 모멘트를 계산할 수 있었다. 이 방법을 reel에 의한 해저배관의 설치 공법에서 사용되는 reverse bending radius 계산에 적용해 보았다.

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Confinement Range of Transverse Reinforcements for T-shaped Reinforced Concrete Walls (철근콘크리트 T형 벽체의 콘크리트 구속을 위한 횡철근의 배근범위)

  • 하상수;오영훈;최창식;이리형
    • Journal of the Korea Concrete Institute
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    • v.14 no.6
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    • pp.1001-1009
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    • 2002
  • The objective of this study is to determine the range of confinement (or the transverse reinforcement of the reinforced concrete structural walls with the T-shaped cross section subjected to cyclic lateral loads. The range of confinement for transverse reinforcement is related to the location of neutral axis and determined by the magnitude and distribution of compressive strain. The compressive strain depends on the ratio of wall cross sectional area to the floor-plan area, the aspect ratio, configuration, the axial load, and the reinforcement ratios. By affection of flange, the neutral axis appears different depending on positive and negative forces and because of this reason, when web and flange are subjected to compressive stress, the range of confinement for the transverse reinforcement of T-shaped walls would shows different result. Therefore this experimental research focused on the structural characteristics of T-shaped walls and suggested the neutral axis depth through comparing the results of this study with sectional analysis.

Control of Position of Neutral Line in Flexible Microelectronic System Under Bending Stress (굽힘응력을 받는 유연전자소자에서 중립축 위치의 제어)

  • Seo, Seung-Ho;Lee, Jae-Hak;Song, Jun-Yeob;Lee, Won-Jun
    • Journal of the Microelectronics and Packaging Society
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    • v.23 no.2
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    • pp.79-84
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    • 2016
  • A flexible electronic device deformed by external force causes the failure of a semiconductor die. Even without failure, the repeated elastic deformation changes carrier mobility in the channel and increases resistivity in the interconnection, which causes malfunction of the integrated circuits. Therefore it is desirable that a semiconductor die be placed on a neutral line where the mechanical stress is zero. In the present study, we investigated the effects of design factors on the position of neutral line by finite element analysis (FEA), and expected the possible failure behavior in a flexible face-down packaging system assuming flip-chip bonding of a silicon die. The thickness and material of the flexible substrate and the thickness of a silicon die were considered as design factors. The thickness of a flexible substrate was the most important factor for controlling the position of the neutral line. A three-dimensional FEA result showed that the von Mises stress higher than yield stress would be applied to copper bumps between a silicon die and a flexible substrate. Finally, we suggested a designing strategy for reducing the stress of a silicon die and copper bumps of a flexible face-down packaging system.

Experimental Study on the Material Characteristics and Flexural Behavior of Ultra High-Strength Concrete (초고강도 콘크리트의 재료특성 및 휨 거동에 관한 실험적 연구)

  • 장영일;이호범;변근주
    • Magazine of the Korea Concrete Institute
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    • v.4 no.2
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    • pp.111-118
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    • 1992
  • 본 연구는 실리카흄을 혼화재료로 사용하여 1200kg/$ extrm{cm}^2$정도의 초고강도 콘크리트를 제조하였으며 이에 대한 재료특성을 실험 및 보부재의 휨거동을 실험을 실시 비교 분석하였다. 재료특성 실험으로는 기본적인 강도 시험, 파괴음 측정에 의한 AE실험 그리고 수은압입법에 의한 세공실험을 실시하였다. 초고강도 콘크리트의 재료특성치는 ACI 363의 고강도 콘크리트 재료특성 결가보다 크게 나타났으며 압축강도와 미세공극량은 선형적으로 비례하였다. 보부재의 휨특성을 파악하기 위해 인장철근비 변화, 전단보강근의 유무 및 철근 표면형상의 변화 등을 실험인자로 하였으며 각각의 현상을 비교분석함으로써 균열성상에 따른 하중-변위 관계, 중립축 이동에 따른 부재거동 및 응력블록의 변화에 관하여 비교 고찰하였다. 초고강도 콘크리트 사용한 보부재의 경우 중립축 상승으로 단면의 압축영역은 매우 작아져 급격히 압축파괴되는 경향을 보였으며 응력블록 형태는 삼각형의 분포를 보였다.

An Experimental Study on Crack Detection of RC Structure using Measured Strain (측정변형률을 이용한 RC 구조물의 균열검출에 관한 실험적 연구)

  • Park, Ki-Tae;Park, Hung-Seok;Lee, Kyu-Wan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.6 no.3
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    • pp.193-199
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    • 2002
  • Structral crack of RC structure generally occurs when the tension stress by applied load is larger than tension resistance of concrete, and it means deterioration of structure and the decrease of load resistance. Because structural crack of structure can occur critical damage to structure occasionally, the research on crack detection algorithm of RC structure is needed for assurance of structural safety and effective maintenance of structure. In this paper, we executed the laboratory test on measuring strain of RC beam's tension and compression zone, using strain gauge which is widely used on strain measurement of civil structure. By using measured strain, we analyzed strain change, elastic modulus change, and neutral axis change to detect crack of RC beam. As a result, we proposed the simple and effective crack detection algorithm using trends of neutral axis position change.

Review of Steel ratio Specifications in Korean Highway Bridge Design Code (Limit States Design) for the Design of RC Flexural Members (철근콘크리트 휨부재 설계를 위한 도로교설계기준(한계상태설계법)의 철근비 규정 검토)

  • Lee, Ki-Yeol;Kim, Woo;Lee, Jun-Seok
    • Journal of The Korean Society of Civil Engineers
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    • v.37 no.2
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    • pp.277-287
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    • 2017
  • This paper describes the specifications on balanced steel ratio and maximum reinforcement for the design of RC flexural members by the Korean Highway Bridge Design Code based on limit states design. The Korean Highway Bridge Design Code (Limit States Design) is not provide for the balanced steel ratio specification for the calculation of required steel area of RC flexural members design. The maximum steel area limited the depth of the neutral axis at the ultimate limit states after redistribution of the moment, and also recommended the maximum steel area should not exceed 4 percent of the cross sectional area. However, from the maximum neutral axis depth provisions should increase the cross section is calculated to be less the maximum reinforcement area, and according to the 4% of the cross sectional area of the concrete, the tensile strain of the reinforcement is calculated to be greater than double the yielding strain, so can not guarantee a ductile behavior. This study developed a balanced reinforcement ratio that is basis for the required reinforcement calculation for tension-controlled RC flexural members design in the ultimate limit states verification provisons and material properties and applied the ultimate strain of the concrete compressive strength with a simple formular to be applied to design practice induced. And assumed the minimum allowable tensile strain of reinforcement double the yielding strain, and applying correction coefficient up to the ratio of maximum neutral axis depth, proposed maximum steel ratio that can be applied irrespective of the reinforcement yield strength and concrete compressive strength.

Investigation and Application of Car Drivers' Mood State (운전자의 무드(mood) 파악 및 활용에 대한 연구)

  • Kim, Yun-Gyeong;Lee, Gyeong-Sil;Seok, Hyeon-Jeong
    • Proceedings of the Korean Society for Emotion and Sensibility Conference
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    • pp.113-116
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    • 2009
  • 보다 바람직한 운전 경험을 제공하기 위하여, 운전자의 감성에 영향을 미치는 요인에 대한 관심이 높아져 가고 있다. 본 연구에서는 운전자의 운전 시의 기분 혹은 감정상태에 영향을 미치는 외부요인으로 도로 소통 상황, 계절, 날씨, 운전 시각, 운전 지역을 추출하였으며 운전자 개인의 감정상태를 결정짓는 주관적이고 심리적인 요인은 배제하였다. 운전 경력 3 년 이상의 운전자를 대상으로 감성 상태는 긍정/부정, 흥분/안정의 2 가지 축으로 나뉘어 측정하였다. 운전자의 무드는 중립을 기준으로 양 극단보다는 중립에 가까운 상태에 주로 분포하였는데 긍정/부정에는 각각 고루 분포한 반면, 흥분/안정에서는 안정 쪽에 더 많이 분포한 것을 알 수 있었다. 또한 다섯 가지 외부 요인들이 모두 운전자의 무드에 영향을 미쳤으며 도로 소통 상황이 긍정/부정과 흥분/안정 모두에서 유의미한 차이를 보였다. 감성의 긍정/부정 축에서는 계절, 날씨, 소통 상황, 그리고 운전 지역이 유의미하였으며, 감성의 흥분/안정 축에서는 운전시간과 소통 상황이 유의미하였다. 본 연구의 결과를 확장시켜 운전자의 감성에 영향을 미치는 외부 요인들을 데이터베이스화하여 운전자를 위한 다양한 제품 및 서비스 개발에 활용될 수 있을 것으로 기대한다.

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Study on Section Properties of Asymmetric-Sectioned Vessels (선박의 비대칭 단면 특성에 대한 연구)

  • Choung, Joon-Mo;Kim, Young-Hun
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.6
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    • pp.843-849
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    • 2010
  • This paper presents definition of symmetry of a ship section where three symmetries are proposed: material, geometric, and load symmetries. Precise terminologies of centroid, moment plane, and neutral axis plane are also defined. It is suggested that force vector equilibrium as well as force equilibrium are necessary condition to determine new position of neutral axis due to translational and rotational mobility. It is also stated that new reference datum of ENMP(elastic neutral moment plane), PNMP(fully plastic moment plane), ENAP(elastic neutral axis plane), and INAP(inelastic neutral moment plane) are required to define asymmetric section properties such as second moment of area, elastic section modulus, yield moment, fully plastic moment, and ultimate moment. Since collision-induced damage and flooding-induced biaxial bending moment produce typical asymmetry of section, the section properties are calculated for a typical VLCC. Geometry asymmetry is determined from ABS and DNV rules and two moment planes of 0/30 degs are assumed for load asymmetry. It is proved that the property reduction ratios directly calculated from second moment of area are usually larger than area reduction ratio. Reduction ratio of ultimate moment capacity shows almost linearly proportional to area reduction ratio. Mobility of elastic and inelastic neutral axis planes is visually provided.

An Experimental Study on Flexural Strength of SC Composite Beams Enforced by Unbonded Post Tension (비부착 포스트텐션 SC합성보의 휨내력에 관한 실험적 연구)

  • Kim, Heui Cheol;Ahn, Hyung Joon;Ryu, Soo Hyun
    • Journal of Korean Society of Steel Construction
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    • v.21 no.2
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    • pp.135-144
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    • 2009
  • This study aims to suggest an appropriate flexural reinforcement technique by evaluating the reinforcement capacity of specimens that underwent flexural reinforcement according to the post-tension method with the anchoring position of an unbonded tension member on the conventional SC composite beam and the applied tension level as variables. For the experiment, up to a predetermined yield load was applied to each type of specimen and then, unbounded post-tensioning was additionally conducted to examine its reinforcement capacity. The analysis of the said experiment showed that the post-reinforced SC composite beam was characterized by significantly improved yield stress and initial stiffness, compared with the pre-reinforced one and the experimental measurements/theoretical values of maximum stress ranged from 0.95 to 1.13 following reinforcement. There was little or no change depending on the maximum stress and tension in the specimen (D160, Class 240) whose neutral axis and upper part had anchoring devices mounted prior to reinforcement. Rather, the ductility decreased with the increasing tension. On the contrary, in the case of the other specimen (Class D120) whose neutral axis had anchoring devices mounted after reinforcement, both the maximum stress and ductility increased with increasing tension, which indicates that the latter tension reinforcement was reasonably appropriate and effective for the neutral axis reinforcement.

Evaluation of Arousal Level Evoked by IAPS (IAPS 사진 자극에 유발된 긴장도 감성 변화의 평가)

  • 전광진;정순철;민병찬;정은지;성은정;강인형;김철중
    • Proceedings of the Korean Society for Emotion and Sensibility Conference
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    • pp.134-137
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    • 2001
  • 본 연구는 International Affective Picture System (IAPS) 사진의 시각 자극을 통해 유발된 감성 변화를 심리ㆍ생리적으로 측정하여 긴장도의 감성 변화를 수행하고자 하였다. 미리 선정된 9개의 사진을 30초씩 제시하면서 ECG, GSR, Skin Temperature, Respiration 등의 생리 신호를 측정하였고, 자극 제시 후 주관적 평가를 실시하였다. 주관적 평가 분석 결과 9개의 사진 중 5종류의 사진에 대한 감성 구분의 가능성이 보였으며, 긴장축으로 긴장 > 불쾌긴장, 쾌긴장 > 중립 > 이완 순서의 4단계로 긴장도가 구분되었다. 자율신경계 반응 또한 긴장영역의 감성을 구분할 수 있었는데, 긴장축으로 긴장, 불쾌긴장, 쾌긴장 > 중립 > 이완 순서의 3단계로 긴장도가 구분되었다. 따라서 각 사진이 유발한 긴장의 감성영역을 주관적 평가를 바탕으로 생리적 반응 분석을 통하여 변별할 수 있을 것으로 판단된다.

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