• Title, Summary, Keyword: 파괴메카니즘

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Failure Mechanism of Headed Reinforcement including Bond Failure (부착파괴를 고려한 Headed Reinforcement의 파괴메카니즘)

  • 박종욱;홍성걸
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.234-237
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    • 2003
  • Previous researches about headed reinforcement have not been concerned about bond failure which is quite important is some cases. In this paper, failure mechanism including bond failure was presented in order to define the contribution of bond stress at the time failure occurs. Examined with design codes and test results, it is proved to be rational to consider the contribution of bond stress in determining the ultimate pull-out capacity of headed reinforcement. Direct adaptation of design code for anchor bolt without modification for the contribution of bond stress will lead to underestimate the capacity of headed reinforcement.

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A study on the Fracture Mechanism and the Test for Strength Properties of the Granite-Gneiss (화강편마암의 강도특성 실험 및 파괴메카니즘에 관한 연구)

  • 최안식;조만섭;김영석
    • Tunnel and Underground Space
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    • v.10 no.2
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    • pp.165-172
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    • 2000
  • When tunnels or underground structures are constructed in anisotropic rock mass, designers and constructors have to consider the anisotropic characteristics in rock mass because their physical and mechanical properties are depended on the anisotropic angles(${\beta}$). In this study, therefore, we have first investigated the mechanical behavior of the gneiss specimen from lab. tests, and then have analysed the behavior of specimens for to the transversely isotropic model in elastic medium using the FLAC program. The results of this study were summarized as follows; 1) In the result of the variation tests, in general, the properties of strength were depended on the angle of inclination in spite of the hard rock. And except for the shear strength test, the lowest and peak stress were appeared at 60$^{\circ}$ and 90$^{\circ}$respectively. 2) The results of specimen modeling analysis using FDM well indicated the mechanical behaviors of the specimen of transversely isotropic model.

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Arrangement of Connections and Piers and Earthquake Resistant Capacity of Typical Bridges (연결부분 및 교각의 배열과 일반교량의 내진성능)

  • Kook, Seung-Kyu
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.2
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    • pp.207-212
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    • 2015
  • Bridges are designed and constructed as infrastructures in order to overcome topographical obstructions for fast and smooth transfer of human/material resources. Therefore the shape and size of piers constructed along the longitudinal bridge axis should be restricted by topographical conditions. Action forces of connections and piers are affected by pier shapes and sizes together with connection arrangement which decides load carrying path under earthquakes. In this study a typical bridge is modelled with steel bearings and reinforced concrete piers and seismic analyses are performed with analysis models with different arrangement of steel bearings and piers. From analysis results ductile failure mechanisms for all analysis models are checked based on strength/action force ratios of steel bearings and pier columns. In this way the influences of arrangement of connections and piers on the earthquake resistant capacity of typical bridges are figured out in view of forming ductile failure mechanism.

A Numerical Study on the Rock Fragmentation by TBM Cutter Penetration (TBM 커터 관입에 의한 암석 파쇄의 수치해석적 연구)

  • 백승한;문현구
    • Tunnel and Underground Space
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    • v.13 no.6
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    • pp.444-454
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    • 2003
  • Rock fragmentation technique by cutter penetration has widely been used in the mechanical tunnel excavation. Microcracks propagate and interact because of locally concentrated high stress induced by cutter penetration. which is caused by heterogeneity of rocks. In this study Weibull distribution function and degradation index are used to consider the strength heterogeneity of a rock and the degradation of rock properties after failure. Through the numerical analyses, it is shown that the lateral pressure has an important influence on the rock fragmentation. In the single cutter penetration, large chips are formed as lateral pressure increase. The cutter spacing is also an important factor that affects the rock fragmentation in the double cutter penetration. The fragmentation efficiency of the double cutter penetration is better when cutter spacing is 70 mm than 40 mm and 100 mm. From the results, it is expected that this study can be applied to a TBM tunnel design by understanding of chipping process and mechanism of rock due to cutter penetration.

A Study on the Safety of Lifting Cable for Construction of Coastal Structures (항만건설을 위한 케이슨 들고리의 안전성에 관한 연구)

  • Kwak, Kae Hwan;Jang, Ki Woong;Kim, Jong Hyo
    • Journal of Korean Society of Steel Construction
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    • v.10 no.1
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    • pp.85-99
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    • 1998
  • This paper describes an experimental study to examine collapse causes of the lifting cable due to brittle failure of an fitting anchor under the lifting works. Also, in this study an collapse mechanism that was obtained from stress analysis was compared with an actual collapse procedure. Fractographical analysis as well as chemical component test, tension test and Charpy V-Notch impact test for the fractured steel members were carried out. And then, its results were compared with that of normal steel members. Circumferential surface flaws were developed at internal facets of the fitting anchor before tensile stress occurred. Hence, a higher stress than nominal stress was occurred at flaws by stress concentration at the crack tip. Also, stress intensity factor of members increased by crack size of the potential flaws. Because the stress intensity factor at the crack tip was greater than critical values(fracture toughness), brittle fracture occurred under the lifting works. It is judged that the main collapse of the lifting cable is due to brittle fracture of the fitting anchor.

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Fracture Mechanism and Characterization of Falling Weight Impact in CF/Epoxy Composite Plates Under Law-Velocity Impact (저속충격 하에서 CFRP 복합적층판의 낙추 충격특성과 파괴기구)

  • 임광희;박노식;김영남;김선규;심재기;양인영
    • Composites Research
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    • v.17 no.4
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    • pp.53-60
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    • 2004
  • This paper describes a method for a falling weight impact test to estimate the impact energy absorbing characteristics and impact strength of CFRP laminate plates based on considerations of stress wave propagation theory. The absorbed energy of T300 orthotropic composites is higher than that of quasi-isotropic specimen over impact energy 6.8J, but in case of using T700 fiber, much difference does not show. Also, absorbed energy of T300 orthotropic composites, which are composed of the same stacking number and orientation became more than that of T700 fiber specimen; however there was no big difference in case of quasi-isotropic specimens. The delamination areas of the impacted specimen were measured with the ultrasonic C-scanner to find correlation between impact energy and delamination area. The fracture surfaces were observed by using the SEM (scanning electron microscope) through a low-velocity impact test in order to confirm the fracture mechanism.

차수용 지오멤브레인의 표면 결함이 물성에 미치는 영향

  • 전한용;김소영;정진희
    • Proceedings of the Korean Fiber Society Conference
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    • pp.303-306
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    • 1998
  • 시트형태의 지오멤브레인은 차수를 목적으로 최근 널리 사용되고 있으며 폐기물 매립장에 적용하기 위한 지오멤브레인은 생산된 후 저장, 이동, 시공 및 시공 후의 다양한 메카니즘에 의해 재료의 표면에 결함이 발생하게 된다 이러한 결함은 지오멤브레인의 역학적 강도의 감소를 초래하여 재료의 파괴를 유도하고 결국은 시스템의 안정성에 문제를 일으킨다. (중략)

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Numerical Study on Failure Mechanism of Tunnel Shotcrete Lining (터널 숏크리트 라이닝 파괴 메커니즘에 대한 수치해석적 고찰)

  • Shin, Hyusoung;Shin, Dongin;Bae, Gyujin;Kim, Donggyu
    • Journal of the Korean Geoenvironmental Society
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    • v.10 no.7
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    • pp.167-177
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    • 2009
  • This study investigates a failure mechanism of a tunnel shotcrete lining with respect to a concentrated load due to blocky rock mass. First of all, it is carried out to survey relevant researches to shotcrete failures by literature reviews and to numerically re-investigate the failure modes of shotcrete lining given by previous researches. Through this study, the failure modes are relocated with the conditions which induce each failure mode newly proposed by this study. In addition to this, the arching shape of tunnel lining, which has not been considered in the previous research despite of inherent geometrical characteristics in tunnels, is taken into consideration in numerical investigation on lining failure in this study. As a result, it is shown that more simplified failure modes can be found on the tunnel boundary condition and the corresponding failure condition to each mode can be different from ones of the previous study due to a tunnel arching effect.

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