• Title, Summary, Keyword: Slip Form

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Development of Early-Strength of High-Strength Concrete According to Curing Temperature for Application of System Form (시스템 거푸집 적용을 위한 고강도 콘크리트의 양생온도별 조기강도 발현성상)

  • 김무한;이승훈;강석표;길배수;주지현
    • Journal of the Korea Concrete Institute
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    • v.13 no.6
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    • pp.536-543
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    • 2001
  • Nowadays, with high-stoned and large-sized of structures, high-strength concrete is applicable to various methods. When high-strength concrete is used jointly with system form, seizing on the development of compressive strength at early age is very important in aspect of construction process. Because system form is stripped more faster than ordinary form. But, we have little data of compressive strength before system-form is stripped, and it isn't yet established that decision criterion of the time when system-form is stripped. So this paper deals with the development of compressive strength at early age before system-form is stripped. In this study, the experimental results indicate the boundary of curing temperature and mixing factor that is able to get needful early-strength in the application of slip-form method, and curing temperature must be kept over 15 degrees in winter season.

Elasto-Plastic Analysis on Connections of Precast Large Panel Structures (프리캐스트 대헝판 구조물의 접합부에 관한 탄소성해석)

  • 권택진;박강근;권익노;조강표
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.27-34
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    • 1993
  • Precast large panel structures behave differently form frame and monolithic wall structures under external loads, because of the distinct planes of weakness in the horizontal and vertical joints between panels. These joints may slide and open during shaking, producing large localized changes in the bending and shear stiffness of individual walls. The structural behavior of large precast panel buildings depends on the relative strength and stiffness of the panels and joints. Special modeling are thus required for the analysis of precast panel connections. This study suggests a new analytical modeling and method to obtain the rational estimation of discontinuity and slip movements form the connections of precast large panel structures .

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Analysis of Bracketed Connection by a Finite Element Method (유한요소법(有限要素法)에 계(係)한 Bracketed Connection의 해석(解析))

  • S.J.,Yim;J.T.,Song
    • Bulletin of the Society of Naval Architects of Korea
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    • v.12 no.1
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    • pp.23-30
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    • 1975
  • Because of the simplicity in analysis and design of steel structure, the connections of members are assumed either as perfectly hinged or rigidly fixed. However, a more economical design would result if the effect of restraint in connections were included in analyzing frame structure. From this point of view, stiffness matrices for member with bracketed connections are presented in the form of the stiffness matrices for member with variable moment of inertia, modified by a correction matrix, whose elements are functions of fixity factors of the connections. To obtain fixity factors, the displacements and stress distribution of bracketed connections are investigated by using of the degital computer program, which have been developed to make computing time shorten and the round off errors smaller. The relationship of moments and slip angle in bracketed connections are presented in the form of curves, which can be used in establishing a stiffness matrices for member with bracketed connections.

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System Reliability Analysis of Slope Considering Multiple Failure Modes (다중 파괴모드를 고려한 사면의 시스템 신뢰도해석)

  • Cho, Sung-Eun
    • Journal of the Korean Geotechnical Society
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    • v.29 no.9
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    • pp.71-80
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    • 2013
  • This work studies the reliability analysis of a slope that considers multiple failure modes. The analysis consists of two parts. First, significant failure modes that contribute most to system reliability are determined. The so-called barrier method proposed by Der Kiureghian and Dakessian to identify significant failure modes successively is employed. Second, the failure probability for the slope is estimated on the basis of the identified significant failure modes and corresponding design points. For reliability problems entailing multiple design points, failure probability can be estimated by the multi-point first-order reliability method (FORM), Ditlevsen's bounds method, and Monte Carlo simulation. In this paper, a comparative study between these methods has been made through example problems. Analysis results showed that while a soil slope may have a large number of potential slip surfaces, its system failure probability is usually governed by a few significant slip surfaces. Therefore, the most important step in the system reliability analysis for a soil slope is to identify all the significant failure modes in an efficient way.

Evolution of Neogene Sedimentary Basins in the Eastern Continental Margin of Korea (한반도 동해 대륙주변부 신제삼기 퇴적분지의 진화)

  • Yoon Suk Hoon;Chough Sung Kwun
    • The Korean Journal of Petroleum Geology
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    • v.1 no.1
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    • pp.15-27
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    • 1993
  • Seismic reflection profiles from the eastern continental margin of Korea delineate three major Neogene sedimentary basins perched on the shelf and slope regions: Pohang-Youngduk, Mukho and Hupo basins. The stratigraphic and structural analyses demonstrate that the formation and filling of these basins were intimately controlled by two phases of regional tectonism: transtensional and subsequent contractional deformations. In the Oligocene to Early Miocene, back-arc opening of the East Sea induced extensional shear deformation with dextral strike-slip movement along right-stepping Hupo and Yangsan faults. During the transtensional deformation, the Pohang-Youngduk Basin was formed by pull-apart opening between two strike-slip faults; in the northern part, block faulting caused to form the Mukho Basin between basement highs. As a result of the back-arc closure, the stress field was inverted into compression at the end of the Middle Miocene. Under the compressive regime, two episodes (Late Miocene and Early Pliocene) of regional deformation led to the destruction and partial uplift of the basin-filling sequences. In particular, during the second episode of compressive deformation, the Hupo fault was reactivated with an oblique-slip sense, which resulted in an opening of the Hupo Basin as a half-graben on the downthrown fault block.

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Measurement of Electrical Resistance Method in Characterizing the Slip ratio of Carbon fiber/Matrix at the Interface (전기저항 측정법을 이용한 탄소섬유/기지 간 계면에서의 섬유 미끌림 정도 측정방법)

  • Kwon, Dong-Jun;Wang, Zuo-Jia;Gu, Ga-Young;Park, Joung-Man
    • Composites Research
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    • v.25 no.6
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    • pp.205-210
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    • 2012
  • The single carbon fiber tensile test was performed with electrical resistance measurement. Tensile property of single carbon fiber which accompanied by the relationship between the electric resistance and the strain was investigated. Since the collected data showed a linear relationship between them, the coefficient of fiber slip ratio (FSR) was obtained by computation. The fragmentation specimen (FS) was tested under tensile loading, and the single carbon fiber broke first due to the stress transferring form matrix to reinforcing fiber. The stress distribution of carbon fiber could be observed via the electrical resistance change. Slipping between carbon fiber and matrix was predicted based on the fragmentation test results, and the FSR was used to evaluate interfacial adhesion comparatively. The large FSR indicated poor interfacial bonding. Work of adhesion between carbon fiber and matrix was measured to verify the FSR method, and two results exhibited a consistent conclusion.

MICROSCOPIC STUDY ON THE STRUCTURE CHANGE OF COPPER BASED ALLOY TO COLD ROLLING AND ANNEALING (동합금(銅合金)의 조직상(組織像)에 관(關)한 연구(硏究))

  • Kim, Yung-Hai
    • Restorative Dentistry and Endodontics
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    • v.4 no.1
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    • pp.7-9
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    • 1978
  • Brass specimen, copper based alloy was prepared in cubic form about $1cm{\times}1cm{\times}1cm$ in volume. The specimens were mechanically compressed in one direction until the dimension distorted to 20%, 40%, 60% and 80% in length. The compressed specimens with 80% distorted in length were then heat treated in $200^{\circ}C$, $300^{\circ}C$, $400^{\circ}C$, $500^{\circ}C$ and $600^{\circ}C$ for 30 minutes. Microscopic examination was made on both compressed and heat treated specimens. The results obtained from the study were as follows: 1. Grain boundary and twin phenomenon was clearly seen in 0% and 20% compressed cases. Slip bands was appeared in 40% cases and distributed equally as well as twin. 2. The first evidence of slip bands was observed in 20% and the bands grew thicker and denser as the compression increased. 3. The density of the bands were reduced after annealing in $200^{\circ}C$ and completely disappeared at $300^{\circ}C$ cases. 4. Recrystallization was noticed unevenly in $300^{\circ}C$ cases and the evidence of twin was observed in these crystallized area. 5. In $400^{\circ}C$ cases the grain boundary was evenly found and the twin phenomenon was clearly observed. Grain boundary and twin was noticeably formed in size according to the annealing temperature increased.

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Yield penetration in seismically loaded anchorages: effects on member deformation capacity

  • Tastani, S.P.;Pantazopoulou, S.J.
    • Earthquakes and Structures
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    • v.5 no.5
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    • pp.527-552
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    • 2013
  • Development of flexural yielding and large rotation ductilities in the plastic hinge zones of frame members is synonymous with the spread of bar reinforcement yielding into the supporting anchorage. Yield penetration where it occurs, destroys interfacial bond between bar and concrete and reduces the strain development capacity of the reinforcement. This affects the plastic rotation capacity of the member by increasing the contribution of bar pullout. A side effect is increased strains in the compression zone within the plastic hinge region, which may be critical in displacement-based detailing procedures that are linked to concrete strains (e.g. in structural walls). To quantify the effects of yield penetration from first principles, closed form solutions of the field equations of bond over the anchorage are derived, considering bond plastification, cover debonding after bar yielding and spread of inelasticity in the anchorage. Strain development capacity is shown to be a totally different entity from stress development capacity and, in the framework of performance based design, bar slip and the length of debonding are calculated as functions of the bar strain at the loaded-end, to be used in calculations of pullout rotation at monolithic member connections. Analytical results are explored parametrically to lead to design charts for practical use of the paper's findings but also to identify the implications of the phenomena studied on the detailing requirements in the plastic hinge regions of flexural members including post-earthquake retrofits.

A study of the variations by motion of the Lower body Using 3D Body Surface Scan Data of a man in his early twenties (3차원 스캐너를 이용한 20대 남성의 하반신 신축량 분석)

  • Sohn, Boo-Hyun;Hong, Kyung-Hi
    • Korean Journal of Human Ecology
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    • v.18 no.3
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    • pp.729-740
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    • 2009
  • This study is to research on the rate of expansion or contraction according to movement of the lower body of the man their twenties using Rapid Form software. And aim of this study is to get information of ease allowance in developing slacks pattern using 3D body surface scan data through comparison with existing slacks patterns. Considering on the contraction and expansion according to movement, it need to set the more ease allowance in hip circumference than waist circumference, and the more ease allowance in back hip width than front hip width in slacks. In crotch length, the length of front crotch is revealed contraction but the length of back crotch is revealed expansion. It is desirable lowering front waist line and raising back waist line to possess ease allowance in back crotch area. The length of side seam is revealed a little expansion but the length of inseam is showed a great expansion. To develop slacks pattern of scientific approach using 3D body surface scan data, it need to analysis the rate of expansion and contraction of the lower body based on the movement, shear deformation, slip in fabrics and skin, or in fabrics and fabrics, and slip down from waist line.

INVESTIGATION OF A STRESS FIELD EVALUATED BY ELASTIC-PLASTIC ANALYSIS IN DISCONTINUOUS COMPOSITES

  • Kim, H.G.
    • International Journal of Automotive Technology
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    • v.8 no.4
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    • pp.483-491
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    • 2007
  • A closed form solution of a composite mechanics system is performed for the investigation of elastic-plastic behavior in order to predict fiber stresses, fiber/matrix interfacial shear stresses, and matrix yielding behavior in short fiber reinforced metal matrix composites. The model is based on a theoretical development that considers the stress concentration between fiber ends and the propagation of matrix plasticity and is compared with the results of a conventional shear lag model as well as a modified shear lag model. For the region of matrix plasticity, slip mechanisms between the fiber and matrix which normally occur at the interface are taken into account for the derivation. Results of predicted stresses for the small-scale yielding as well as the large-scale yielding in the matrix are compared with other theories. The effects of fiber aspect ratio are also evaluated for the internal elastic-plastic stress field. It is found that the incorporation of strong fibers results in substantial improvements in composite strength relative to the fiber/matrix interfacial shear stresses, but can produce earlier matrix yielding because of intensified stress concentration effects. It is also found that the present model can be applied to investigate the stress transfer mechanism between the elastic fiber and the elastic-plastic matrix, such as in short fiber reinforced metal matrix composites.