• Title/Summary/Keyword: Punching analysis

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Study on Behavior of Failure of Footing through Numerical Analysis (수치해석을 통한 기초지반의 파괴거동 고찰)

  • Lee, Seung-Hyun;Jang, In-Sung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.3
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    • pp.2212-2218
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    • 2015
  • In order to find out the load bearing behavior of sand and clay which sustain three types of shallow footing, finite element analyses were performed. Failure zone of sand which sustain strip footing was affected by relative density of sand whereas, failure zone of clay was not affected by soil strength and it was similar to the failure zone which is considered in theory. Considering the shape of load-settlement curves obtained by numerical analyses, punching shear failure can be seen in loose sand and ultimate bearing load can not be seen in dense sand whereas, yielding point can be seen in clay. Ultimate bearing loads for sand predicted by theory were greater than those obtained by numerical analyses and ultimate bearing loads for clay predicted by theory were similar to those of numerical analyses. Ultimate bearing loads determined by 1 inch settlement criteria were slightly less than those of numerical analyses.

Stability Analysis and Application Evaluation of the Pretensioned Soil Nailing Systems (프리텐션 쏘일네일링 시스템의 안정해석 및 적용성 평가)

  • Kim, Hong-Taek;Park, Si-Sam
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.783-790
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    • 2004
  • In this study, a newly modified soil nailing technology named as the PSN(pretensioned soil nailing) system, is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the PSN system has been investigated mainly focusing on an establishment of the design procedure. In the present study, the analytical procedure and design technique are proposed to evaluate maximum pretension force and stability of the PSN system. Also proposed arc techniques to determine the required thickness of a shotcrete facing and to estimate probability of a failure against the punching shear. Based on the proposed procedure and technique, effects of the radius of a influence circle and dilatancy angle on the thickness of a shotcrete facing, bonded length and safety factors arc analyzed. In addition, effects of the reduction of deformations expected by pretensioning of the soil nails are examined in detail throughout an illustrative example and $FLAC^{2D}$ program analysis. And a numerical approach is further made to determine a postulated failure surface as well as a minimum safety factor of the proposed PSN system using the shear strength reduction technique with the $FLAC^{2D}$ program. Global minimum safety factors and local safety factors at various excavation stages computed in case of the PSN system arc analyzed throughout comparisons with the results expected in case of the general soil nailing system. The efficiency of the PSN system is also dealt with by analyzing the wall-facing deformations and the adjacent ground surface settlements.

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Seismic Performance of Post Tensioned Flat Plate Structures according to Slab Bottom Reinforcement (하부 철근 유무에 따른 포스트 텐션 플랫 플레이트 골조의 내진성능 평가)

  • Han, Sang-Whan;HwangBo, Jin;Ryu, Jong-Hyuk;Park, Young-Mi
    • Journal of the Earthquake Engineering Society of Korea
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    • v.12 no.4
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    • pp.11-17
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    • 2008
  • This study evaluates the seismic performance of post-tensioned flat plate structures with or without slab bottom reinforcement. For this purpose, 3 and 9 story frames were designed only considering gravity loads. This study conducts a nonlinear static pushover analysis. This study was an analytical model that is able to represent punching shear failure and fracture mechanism. The analytical results showed that the seismic performance of a post-tension flat plate is strongly influenced by the existence of slab bottom reinforcement through column. By placing slab bottom reinforcement in a PT flat plate frame, lateral strength and max drift capacity are significantly increased.

Usage Analysis and Design Development for Pilot Gloves (비행장갑설계를 위한 사용실태분석 및 개선안 개발)

  • Park, Ji-Eun;Jeon, Eun-Jin;Jeong, Jeong-Rim;Park, Sei-Kwon;You, Hee-Cheon;Kim, Hee-Eun
    • Fashion & Textile Research Journal
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    • v.11 no.5
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    • pp.764-770
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    • 2009
  • This study was conducted to analyze the wearing condition on gloves for pilots and to suggest the developments for pilot gloves design. This survey was performed with 99 pilots and the questionnaires included items about discomfort, materials and problems when wearing pilot gloves. The respondents felt uncomfortable on the finger tip, the hollow area of the hand and the end of thumb when they move their hands with the gloves. They replied that the finger length, palm length, and circumference of the fingers did not match well. Also they complained there was severe abrasion in the tip of the thumb, finger tips and the middle of the palm of the gloves. The result of these analyses supports the following suggestions. It is necessary to improve durability by applying the additional materials to the severely worn parts. Punching on the glove materials could improve sweat rate and ventilation, and careful washing should be accompanied to prevent the occurrence of linters and transformation after laundering. And it is needed to prepare an accurate and more diversified size system and to design the gloves fitted to the individual hands. With these in mind, it is required to propose solutions for pilot gloves with reference to the survey results in order to design appropriate pilot gloves in terms of movement, size and material. It was concluded that an analysis of the wearing condition and developments are useful for ergonomics pilot gloves design.

Analysis of Stratified Rock under Vertical Load in Pile Foundation of Wind Turbine Using Circular Foundation Analysis Method with Equivalent Effective Width (등가유효폭을 가진 원형기초해석법을 이용한 풍력발전기 말뚝기초의 연직하중에 대한 층상암반 해석)

  • Kim, Dohan;Park, Sangyeol;Moon, Kyoungtae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.6
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    • pp.2411-2425
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    • 2013
  • In the design of pile foundation on the rock layer in the stratified structure with sedimentary and rock layers, the structural analysis of the stratified rock layer is required to determine the failure modes (flexural failure, punching shear failure or end bearing failure) and the bearing capacity of the rock layer. However, the existing usable Elastic Plate Analysis Method (EPAM) suggested by ACI committee 436 and Korean Code Requirements for Structural Foundation Design is very complex, and engineers have many difficulties in using it. Therefore, in this research, we proposed the relatively simple Circular Foundation Analysis Method (CFAM) with the concept and the equation of the equivalent effective width (radius) instead of the complex EPM, and the related equations of bending moment and shear force to be equal to the analysis results of EPAM. As a result, the proposed CFAM using the equivalent effective width (radius) is simple and convenient to use, and the analysis results of it are very good in their accuracies comparing those of EPAM and Finite Element Method.

Tensile-Shear Fatigue Strength of Self-Piercing Rivets Joining Dissimilar Metal Sheets (이종재료 Self-Piercing Rivets 접합부의 인장-전단 피로강도)

  • Kang, Se Hyung;Kim, Taek Young;Oh, Man Jin;Kim, Ho Kyung
    • Journal of the Korean Society of Safety
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    • v.30 no.4
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    • pp.1-7
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    • 2015
  • Self-piercing riveting (SPR) process is gaining popularity due to its many advantages. The SPR does not require a pre-drilled hole and has capability to join a wide range of similar or dissimilar materials and combinations of materials. This study investigated the fatigue strength of self-piercing rivet joint with aluminum alloy (Al-5052) and steel (SPCC) sheets. Static and fatigue tests on tensile-shear specimens were conducted. From the static strength aspect, the optimal punching force for the specimen with upper SPCC (U.S) sheet and lower aluminum alloy(L.A) sheets was 34 kN. During static test the specimens fractured in pull-out fracture mode due to influence of plastic deformation of joining area. There was a relationship between applied load amplitude $P_{amp}$ and number of cycles N ; $P_{amp}=19588N_f^{-0.211}$ and $P_{amp}=4885N_f^{-0.083}$ for U.S-L.A and U.A-L.S specimens, respectively. U.A-L.S fatigue specimens failed due to fretting crack initiation around the rivet neck between upper and lower sheets.

An Analysis on Punching Shear of Two-way Void Slab (이방향 중공슬래브-기둥 접합부 뚫림전단성능의 해석적 평가)

  • Lee, Yung Eun;Ryu, Jaeho;Ju, Young Kyu;Kim, Sang Dae
    • 한국방재학회:학술대회논문집
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    • 2011.02a
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    • pp.32-32
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    • 2011
  • 최근 국내외에서 친환경건축물에 관한 관심이 매우 높아짐으로 인해 콘크리트의 물량을 절감하여 이산화탄소량을 줄이는 중공슬래브는 다양한 형태로 세계적으로 개발이 되고 있는 추세이다. 특히 이방향 중공슬래브는 환경적인 측면에서 이방향 중공슬래브는 중공부 생성에 재생플라스틱을 활용하여 폐자원을 재사용하고, 콘크리트와 철근의 사용량 절감에 따른 화석에너지 및 이산화탄소 발생량을 감소한다는 장점이 있다. 또한 시스템 측면에서 이방향 중공슬래브는 기존의 철근콘크리트 플랫플레이트 바닥구조 시스템의 자중을 절감하여 구조체를 경량화 시키고, 이에 따라 장스팬 구현이 가능하며, 단열효과가 뛰어나다. 이와 같이 이방향 중공슬래브는 장점이 많지만 플랫플레이트 슬래브의 취약점인 뚫림전단 파괴에 주의해야 한다. 이에 본 연구에서는 선행으로 실시된 이방향 중공슬래브-기둥 접합부 뚫림전단 성능평가 실험을 바탕으로 하여 경량체가 이방향 중공슬래브-기둥 접합부 뚫림전단 성능에 미치는 영향을 살펴보기 위해 범용 유한요소해석 프로그램인 ABAQUS를 사용하여 경량체량 및 위치를 주요변수로 한 해석적인 변화를 검토하였다. 본 연구를 통해 경량체가 삽입된 이방향 중공슬래브의 뚫림전단 성능에 대해, 해석결과 경량체 량과 위치에 따라 최대 뚫림전단강도는 기준 실험체에 비해 74.3%, 73%의 강도저하를 나타내는 것으로 알 수 있었다. 이는 실험상의 강도저하 값인 84.1%, 56.4%와 다소 차이가 있으며, 해석에서 중공부 주위의 응력집중 현상이 제대로 반영되지 않은 것으로 판단된다. 또한 이방향 슬래브에 경량체를 삽입 할 경우 경량체가 시작하는 부분에서 응력이 급격히 감소하는 현상이 나타났으며, 이러한 급격한 응력감소는 기둥 주위 위험단면의 변화를 가져오는 것으로 추정된다. 즉, 위험단면의 변화는 기둥으로부터 경량체 사이의 거리에 따라 달라지며, 위험단면 내의 콘크리트 단면 손실은 뚫림전단 강도를 감소시킨다. 본 연구에서는 이방향 중공슬래브의 뚫림전단강도를 산정할 수 있는 근사식을 제안하였으며, 보다 정확한 이방향 중공슬래브의 뚫림전단강도의 산정식을 위해서는 위험단면의 변화와 콘크리트 단면손실로 인한 전단강도 저하의 관계에 대한 추가적인 연구가 필요하다.

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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 GEO-environmental 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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A Study on the Forming Characteristics of Clinching Joint Process (크린칭 접합의 성형특성에 관한 연구)

  • Jayasekara, V.R.;Noh, J.H.;Hwang, B.B.;Ham, K.C.;Jang, D.H.
    • Transactions of Materials Processing
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    • v.16 no.8
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    • pp.603-613
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    • 2007
  • This paper is concerned with joining of thin metal sheets by single stroke clinching process. This method has been used in sheet metal work as it is a simple process and offers the possibility of joining similar-dissimilar thin sheet metals. Clinching generates a joint by overlapping metal sheets deforming plastically by punching and squeezing sequence. AA 5754 aluminum alloy of 0.5 mm thick sheets have been selected as a modal material and the process has been simulated under different process conditions and the results have been analyzed in terms of the quality of clinch joints which are influenced mainly by tool geometries. The rigid-plastic finite element method is applied to analyses in this paper. Analysis is focused mainly on investigation of deformation and material flow patterns influenced by major geometrical parameters such as die diameter, die depth, groove width, and groove corner radius, respectively. To evaluate the quality of clinch joints, four controlling or evaluation parameters have been chosen and they are bottom, neck thickness of bottom and top sheets, and undercut thickness, respectively. It has been concluded from the simulation results that the die geometries such as die depth and diameters are the most decisive process parameters influencing on the quality of clinch joints, and the bottom thickness is the most important evaluation parameter to determine if the quality of clinch joints satisfies the demand for industrial application.

Strength of Exterior Flat Plate-Column Connections Subjected to Unbalanced Moment (불균형 휨모멘트를 받는 플랫 플레이트-기둥 외부접합부의 강도)

  • Choi, Kyoung-Kyu;Park, Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.15 no.3
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    • pp.470-481
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    • 2003
  • Exterior plate-column connection has an unsymmetrical critical section for eccentric shear of which perimeter is less than that of interior connection, and hence, around the connection, unbalanced moment and eccentric shear are developed by both gravity load and lateral loads. Therefore, exterior connection is susceptible to punching shear failure. Current design provision cannot accurately explain strength of existing experiments, partly due to the complexity in the behavior of exterior plate-column connection, or partly due to the theoretical deficiency of the strength analysis model adopted. In the present study, nonlinear finite element analyses were performed for exterior connections belonging to continuous flat plate. For each direction of lateral load, the behavior and strength of exterior plate-column connection were quite different. Based on the numerical result, strength prediction model for exterior connection was proposed for each direction of lateral load. Compared with existing experiments, the proposed method was verified.