• Title/Summary/Keyword: 반복 수평하중

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Effects of Loading Method on the Behavior of Laterally Cyclic Loaded Piles in Sand (모래지반에서 재하방법이 반복수평하중을 받는 말뚝의 거동에 미치는 영향)

  • Paik, Kyu-Ho;Kim, Young-Jun;Lee, Seung-Yeon
    • Journal of the Korean Geotechnical Society
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    • v.27 no.3
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    • pp.63-73
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    • 2011
  • The behavior of laterally cyclic loaded piles is affected by the magnitude and number of cycles of cyclic lateral loads as well as loading method (1-way or 2-way loading). In this study, calibration chamber tests were carried out to investigate the effects of loading method of cyclic lateral loads on the behavior of piles driven into sand. Results of the chamber tests show that the permanent lateral displacement of 1-way cyclic loaded piles is developed in the same direction as the first loading, whereas that of 2-way cyclic loaded piles is developed in the reverse direction of the first loading. 1-way cyclic lateral loads cause a decrease of the ultimate lateral load capacity of piles, and 2-way cyclic lateral loads cause an increase of the ultimate lateral load capacity of piles. The change of ultimate lateral load capacity with loading method of cyclic lateral loads increases with increasing number of cycles. It is also observed that the 1-way cyclic loads generate greater maximum bending moment than 2-way cyclic loads for piles in cyclic loading step and generates smaller maximum bending moment for piles in the ultimate state. It can be attributed to the difference in compaction degree of the soil around the piles with loading method of cyclic lateral loads. In addition, it is founded that 1-way and 2-way cyclic lateral loads cause a decrease in the maximum bending moment of piles in the ultimate state compared with that of piles subjected to only monotonic loads.

Surface damage accumulation in alumina under the repeated Inclined contact forces (수직-수평 반복하중을 받는 알루미나 표면에서의 피로손상 누적)

  • 이권용;최성종
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1999.06a
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    • pp.61-66
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    • 1999
  • 반복 응력 상태 아래서 알루미나 세라믹의 피로 표면손상 누적현상이 분석되었다. 연속 미끄럼 접촉 시에 발생하는 응력 상태를 재현하기 위해서 동시에 작용하는 수직-수평 반복 압축하중 기법이 사용되었다. 알루미나 구와 평판의 접촉면에서 알루미나 미세 결정의 피로 파손에 의한 마모 입자 형성 기구가 관찰되었고, 반복하중의 횟수와 수직-수평 하중비가 커질수록 마모량은 증가하였다. 반복 접촉하중에 의한 표면손상 누적이 접촉 수직 변위 측정으로 정량화 되었다. 두 접촉 구조물의 강성 (하중-변위 선도의 기울기) 변화가 두 재질의 탄성계수의 변화로 표현되었다.

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Lateral Behavior of Driven Piles Subjected to Cyclic Lateral Loads in Sand (모래지반에서 반복수평하중을 받는 항타 말뚝의 수평거동)

  • Paik, Kyu-Ho
    • Journal of the Korean Geotechnical Society
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    • v.26 no.12
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    • pp.41-50
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    • 2010
  • The behavior of laterally cyclic loaded piles is different from that of piles under monotonic loading and depends on soil and load characteristics. In this study, model pile load tests were performed using a calibration chamber to investigate the effects of load characteristics on the behavior of laterally cyclic loaded piles in sand. Results of the model tests show that the ultimate lateral load capacity of laterally cyclic loaded piles decreases linearly with increasing the number of cycles and increases slightly with increasing the magnitude of cyclic lateral loads. When the piles reach the ultimate state, the maximum bending moment developed in the piles decreases linearly with increasing the number of cycles and it occurs at a depth of 0.36 times pile embedded length for all the number of cycles. However, both the magnitude and depth of the maximum bending moment of piles in the ultimate state increase slightly as the magnitude of cyclic lateral loads increases. It is also observed that the cyclic lateral loading generates a decrease in the ultimate lateral load capacity and maximum bending moment for piles in the ultimate state. In addition, based on the model test results, a new empirical equation for the ultimate lateral load capacity of laterally cyclic loaded piles in dense sand is also proposed. A comparison between predicted and measured load capacities shows that the proposed equation reflects satisfactorily the model test results.

Permanent Deformations of Piles in Sand Under Cyclic Lateral Loads (모래지반에서 반복수평하중을 받는 말뚝의 영구변형)

  • Paik, Kyu-Ho;Park, Won-Woo
    • Journal of the Korean Geotechnical Society
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    • v.26 no.11
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    • pp.63-73
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    • 2010
  • Monopiles, used as one foundation option for offshore wind turbines, are usually subjected to great cyclic lateral loads due to wind and wave. In this study, model pile load tests were performed using calibration chamber and three model piles with different pile lengths in order to investigate the behavior of laterally cyclic loaded piles driven into sand. Model test results show that the first loading cycle generates a bigger displacement than the following ones, and the permanent displacement of piles by one loading cycle decreases with increasing the number of cycles. 1-way cyclic loading causes the permanent displacement in the same direction as cyclic loading, whereas 2-way cyclic loading causes the permanent displacement in the reverse direction of initial loading. It is also observed that the permanent displacement of piles due to cyclic lateral loads increases with decreasing relative density of soil and with increasing the magnitude of cyclic loads. However, it is insensitive to the earth pressure ratio of soil and embedded pile length. In addition, based on the model pile load test results, equations for estimation of the permanent lateral displacement and rotation angle of piles due to 1-way cyclic lateral loads are proposed.

Study on the Strength of Limit Axial Force and Accumulated Limit Axial Force of Concrete Filled Square Tube Columns (콘크리트 충전 각형강관 기둥부재의 한계축력 및 누적한계축력에 관한 연구)

  • Seo, Seong Yeon;Jung, Jin Ahn;Kim, Sung Yong
    • Journal of Korean Society of Steel Construction
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    • v.17 no.5 s.78
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    • pp.605-615
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    • 2005
  • Experimental and analytical work was conducted to investigate the relations of axial force and deformational capacity of concrete-filled square steel tube columns. The test series consisting of 36 columns were tested under the constant axial load and horizontal cyclic load. The axial force of the columns that resisted under the cyclic lateral load was defined as a certified strength of limit axial force. The analytical model was defined as a cantilever beam-column. The axial force of the beam-column that resisted under the cyclic lateral load was defined as an accumulated certified strength of limit axial force. The purpose of this study is to investigate the certified strength of limit axial force of concrete-filled steel tube beam-columns, which were subjected to both axial and lateral load condition corresponding to a given constant rotation angle. Another purpose of this study is to discuss the comparison of the certified strength of limit axial force of concrete and the accumulated certified strength of limit axial force of concrete-filled steel tube columns.

Behaviour Characteristics of Single Batter Pile under Dynamic Lateral Loads (동적 수평하중에 의한 단일 경사말뚝의 거동특성)

  • Kim, Jiseong;Noh, Jeongseob;Kang, Gi-Chun
    • Journal of the Korean Geotechnical Society
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    • v.33 no.9
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    • pp.49-60
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    • 2017
  • The purpose of this study is to investigate the behavior of a single batter pile with repeated lateral loading through model tests. Repeated loads were applied in one direction and two directions, and lateral resistance and bending moment were analyzed by varying the relative density of the ground. As a result, lateral resistance and maximum bending moment were increased in the order of Out batter, Plumb, and In batter when one-way and two-way dynamic lateral loads were applied. The depth at the maximum bending moment was more deeper with the loading. The moments at bottom layer were decreased in the order of Out batter, Plumb, and In batter but upper moments were increased with the same order. Also, various bottom and upper moments were small when the two-way dynamic lateral load was applied compared to one-way lateral load.

Small Scale Modelling Experiments for Evaluating Lateral Resistance of Block-Type Breakwater II: A Single Block Reinforced with Piles under Cyclic Lateral Loads (블록식 방파제의 수평저항력 평가를 위한 실내모형실험 II : 보강형 싱글블럭의 반복수평 하중에 대한 저항)

  • Kang, Gichun;Kim, Jiseong
    • Journal of the Korean Geosynthetics Society
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    • v.20 no.4
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    • pp.105-112
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    • 2021
  • In the case of harbor structures, it is important to understand the characteristics of structures that are subjected to repeated loads as they are structures that receive repetitive loads such as wave pressure as well as static loads. In this study, the lateral resistance according to the pile embeded depth of the block breakwater reinforced with piles by cyclic lateral loads was obtained through an model experiment. As the depth of embedment of the pile increased, the lateral resistance showed a tendency to increase. As the load was repeated, the gradient of the lateral resistance gradually appeared to be gentle. The bending moment of the rear pile was larger than that of the front pile. The bending moment of piles in the ground was similar to that when the pile head was free in the cohesionless of Broms (1964).

Experimental Study on the Behavior Characteristics of Single Steel Pile in Sand Subjected to Lateral Loadings (사질토 지반에서 수평하중에 따른 단일강관말뚝의 거동특성에 관한 실험적 연구)

  • Kim, Daehyeon;Lee, Tae-Gwang;Kim, Sun-Hak
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.5
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    • pp.3548-3556
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    • 2015
  • In order to fulfill the needs of reliable and economically feasible foundation, engineers should consider not only the working load that can endure extreme conditions but also apprehending precise behavior of continuous dynamic load while designing the foundation of offshore wind power generators. To actualize the foundation, a model pile was made in miniature. Also, calibration chamber was made and a 500mm height of sand-bed was made to perform "static lateral load experiment" and "repetitive loading experiment", total of two Lateral load tests. As a result, in Static Lateral load test, the bigger length/diameter of model pile led an increase in load displacement. However, when performing "Cyclic Lateral load test", the increase in number of under loading led the decrease in horizontal displacement from each repeated lateral load. While performing Static Lateral load test and repeated loading experiment, we could observe the decreasing in the rate of ultimate lateral load capacity increase of the pile. Also, it turned out that the higher relative density of the ground, the lower ultimate lateral load capacity by repeated horizontal loading.

Evaluation of Permanent Lateral Displacement of a Cyclic Laterally Loaded Pile in Sandy Soil (모래지반에서 횡방향 반복하중을 받는 말뚝의 영구수평변위 평가)

  • Baek, Sung-Ha;Kim, Joon-Young;Lee, Seung-Hwan;Chung, Choong-Ki
    • Journal of the Korean Geotechnical Society
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    • v.33 no.2
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    • pp.17-26
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    • 2017
  • Pile foundations that support offshore structures or transmission towers are dominantly subjected to cyclic lateral loads due to wind and waves, causing permanent displacement which can severely affect stability of the structures. In this study, a series of cyclic lateral load tests were conducted on a pre-installed aluminum flexible pile in sandy soil with three different relative densities (40%, 70% and 90%) in order to evaluate the permanent displacement of a cyclic laterally loaded pile. Test results showed that the cyclic lateral loads accumulated the irreversible lateral displacement, so-called permanent displacement. As the number of cyclic lateral load increased, accumulated permanent displacement increased, but the permanent displacement due to one loading cycle gradually decreased. In addition, the permanent displacement of a pile increased with decrement of relative density and decreased by soil saturation. From the test results, the normalized permanent displacement defined as the cumulative permanent displacement to the initial permanent displacement ratio was investigated, and empirical equations for predicting the normalized permanent displacement was developed in terms of relative density of the soil and the number of cyclic lateral load.

Proposed Reduction Factor of Cyclic p-y Curves for Drilled Shafts in Weathered Soil (풍화토 지반에 근입된 현장타설말뚝의 Cyclic p-y 곡선의 감소계수 제안)

  • Kim, Byung-Chul;Jeong, Sang-Seom;Ko, Jun-Young
    • Journal of the Korean Geotechnical Society
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    • v.31 no.2
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    • pp.47-63
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    • 2015
  • A fundamental study of drilled shafts subjected to lateral cyclic loading in weathered soil was carried out based on field tests and numerical analysis. The emphasis was given on quantifying the cyclic p-y curve function from lateral cyclic loading tests and three-dimensional finite element analysis. Lateral cyclic loading tests and three-dimensional finite element analysis were carried out to investigate the behavior of drilled shafts according to the direction of cyclic loading. Based on the field tests and numerical analysis, a modified lateral load transfer relationship and design chart with degradation factors were proposed by considering the characteristics of cyclic loading. It was found that the prediction by the proposed p-y curve function is in good agreement with the general trends observed by in-situ measurements, and it represents a practical improvement in the prediction of lateral displacement and bending moment distribution of drilled shafts subjected to cyclic loading.