• Title, Summary, Keyword: Yield Load

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Evaluation of Yield Load in Pile Load Tests on Driven Piles (관입말뚝에 대한 연직재하시험시 항복하중의 판정법)

  • 홍원표;심기석
    • Geotechnical Engineering
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    • v.5 no.1
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    • pp.7-18
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    • 1989
  • In pile load tests on end bearing piles, generally, it is not possible to continue loading to the ultimate load. Thus, the concept of yield load has been introduced for determining design loads Iron the pile load test records. The conventional rules to determine the yield load were not available for evaluation on pile load test records obtained in 6 fields nearby westers 8r Southern Coasts in Korea. A new rule 9.as presented to determine easily the yield load, based on investigations on the pile load test records. The yield load of piles is determined at the infiection point on semi-logarithmic coordinates (P-logS), in which load is plotted in normal scale and settlement is plotted in logarithmic scale. This method may not only save much costs and times but also present safe luorking circumstances for pile load tests in field. It was found that the yield load represented the elastic limit of the pile load-settlement behalf.iota. The ultimate load, which is given at 25.4mm settlement on pile head, was 1.5 times of the yield load. The allowable long-term and short-term load capacities were, respectively, 50% and 75% of the yield load. The safety factors to get the allowable pile capacity were obtained as 2.0~4.0 for the equations to predict the static pile capacity.

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A Study on Prevent Delamination of Strengthening Material (보강재의 탈락 방지 방안 연구)

  • 한만엽;백승덕
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.809-814
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    • 1998
  • Recently many cases that using strengthening method with a steel plate or carbon-fiber sheet in a construction field are increasing. In this reason, it is demanded that developing a plan of preventing delamination of strengthening material. So in this research, for the case of strengthening method of steel plate, it is made use of notch and anchor bolt and for the case of carbon fiber sheet, it is made use of notch, anchor bolt, line anchor and shear strengthening. After all the cases were applied, we made 15 specimen beams. The beams was measured and analyzed about the behavior property of strengthened beams, the ability strengthening method, the relation between load and the shape of failure, the crack load, the yield load, the shape of crack pattern, the increasing rate from yield load and maximum load and the strain of rebar. All the strengthening methods results in almost same value until the yield load, and it wasn't quite different from the theoretical value. But for the case of increasing rate from the yield load and maximum load, comparing with the existing method, the new strengthening methods are proved to be profitable about the safety.

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Relations of Safety Factor and Reliability Index for Pile Load Capacity (말뚝 기초지지력에 대한 안전율과 신뢰도지수 평가)

  • Kim, Dae-Ho;Lee, Jun-Hwan
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.466-475
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    • 2006
  • Reliability analysis between safety factor and reliability index for driven and bored pile load capacity was analyzed in this study. 0.1B, Chin, De Beer, and Davisson's methods were used for determining pile load capacity by using load-settlement curve from pile load test. Each method define ultimate, yield and allowable pile load capacities. LCPC method using CPT results was performed for comparing with results of pile load test. Based on FOSM analysis using load factors, it is obtained that reliability indices for ultimate pile load capacity were higher than those of yield and allowable condition. Present safety factor 2 for yield and allowable load capacities are not enough to satisfy target reliability index $2.0\sim2.5$. However, it is sufficient for ultimate pile load capacity using safety factor 3.

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Axial Load Transfer Behavior for Driven Open-ended End bearing Steel Pipe Pile (선단지지된 항타개단강관말뚝의 축하중전이거동)

  • 임태경;정성민;정창규;최용규
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.589-596
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    • 2002
  • In this study, static pile load tests with load transfer measurement were accomplished in the field. Yield pile capacity (or ultimate pile capacity) determined by load-settlement-time relationship was determined and axial load transfer behavior was analyzed. In the test for the four test piles were behaved as end bearing pile but ratios of skin friction to total pile capacity were 27%∼33%.

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A Study on Physical Behavior Property of R/C Beams Strengthened with Bonding Methods (보강재의 부착방법의 따른 물리적 거동 특성에 관한 연구)

  • 한만엽;백승덕
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.727-732
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    • 1999
  • In this research, we made an experiment on the 10 specimen beams that we made. The specimen beams consist of 4 steel plate strengthening beams and 5 carbon fiber sheet strengthening beams. We applied the methods of notch, rounding off a edge, anchor bolt and side shear strengening to the steel plate and for the case of carbon fiber sheet, we applied the methods of anchor bolt, line anchor and shear strengthening. After all the cases were applied, the beams was measured and analyzed about the behavior property of strengthened beams, th ability of strengthening method, the relation between load and the shape of failure, the crack load, the yield load, the shape of crack pattern, the increasing rate from yield load and maximum load and the strain of rebar. All the strengthening methods resulted in almost same value until the yield load, and it wasn't quite different from the theoretical value. In comparison with existing method, the SER, SEAS for the steel plate and the CEA, CESS, CCESS for carbon fiber sheet showed the increasement of ductility with big displacement.

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Yield Load Interpretation for Drilled Shaft Foundations by Hyperbolic Approximation (쌍곡선 근사에 의한 현장타설말뚝의 항복하중 판정)

  • Won, Sang-Yeon;Hwang, Seong-Il;Jo, Nam-Jun
    • Geotechnical Engineering
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    • v.12 no.6
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    • pp.79-86
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    • 1996
  • This study develops a new method for interpreting the yield load from load tests on drilled shaft foundations ended on general soils, which is defined as a point where the maximum curvature on the hyperbolic-approximated load-settlement curve occurs. How ever, the point of maximum curvature is a variable depending on the units and scales of the load and settlement. Therefore, to obtain a unique maximum curvature point, both the load and settlement must be normalized by proper parameters, respectively, and be expressed on the same scaled arses(1:1). Normalization has been processed so that the yield load by the new interpretation is to be close to the average of yield loads interpreted by other methods investigated in this study. The quantitative comparison between the new criterion and other conventitonal methods is presented.

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Evaluation of Limit Load of Granular Pavement Materials Considering Unsaturated Shear Strength Characteristics (불포화 강도특성을 고려한 도로 입상재료의 한계하중 평가)

  • Jeon, Hye-Ji;Park, Seong-Wan
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.673-678
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    • 2010
  • In this paper, the limit load of granular materials was evaluated considering unsaturated shear strength. The unsaturated shear strength parameters were estimated using the results from triaxial compression test and soil-water characteristic curves test. In addition, the limit load of different rates of materials was compared. Also, two important design parameters, yield and failure load were defined utilizing 2-D nonlinear finite element analysis respectively.

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Behavioral Mechanism of Hybrid Model of ABG: Field Test (현장시험을 통한 ABG 하이브리드 공법의 거동 메커니즘 분석)

  • Seo, Hyung-Joon;Kim, Hyun-Rae;Jeong, Nam-Soo;Lee, In-Mo
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.523-534
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    • 2010
  • A hybrid system of soil-nailing and compression anchor is proposed in this paper; the system is composed of an anchor bar (installed at the tip) with two PC strands and a steel bar. After drilling a hole, installing proposed hybrid systems, and filling the hole with grouting material, prestress is applied to the anchor bar to restrict the deformation at the head and/or to prevent shallow slope failures. However, since the elongation rate of PC strand is much larger than that of steel bar, yield at the steel bar will occur much earlier than the PC strand. It means that the yield load of the hybrid system will be overestimated if we simply add yield loads of the two - anchor bar and PC strands. It might be needed to try to match the yielding time of the two materials by applying the prestress to the anchor bar. It means that the main purpose of applying prestress to the anchor bar should be two-fold: to restrict the deformation at the nail head; and more importantly, to maximize the design load of the hybrid system by utilizing load transfer mechanism that transfers the prestress applied at the tip to the head through anchor bar. In order to study the load transfer mechanism in a systematic way, in-situ pullout tests were performed with the following conditions: soil-nailing only; hybrid system with the variation of prestress stresses from 0kN to 196kN. It was found that the prestress applied to the anchor system will induce the compressive stress to the steel bar; it will result in decrease in the slope of load-displacement curve of the steel bar. Then, the elongation at which the steel bar will reach yield stress might become similar to that of PC strands. By taking advantage of prestress to match elongations at yield, the pullout design load of the hybrid system can be increased up to twice that of the soil-nailing system.

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Settlement Characteristics of Large Drilled Shafts Embedded in Bed Rocks (암반에 근입된 대구경 현장타설말뚝의 침하특성)

  • Hong Won-Pyo;Yea Geu-Guwen;Nam Jung-Man;Lee Jae-Ho
    • Journal of the Korean Geotechnical Society
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    • v.21 no.5
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    • pp.111-122
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    • 2005
  • The data on the pile load tests performed on 35 large drilled shafts are analyzed to investigate the load-settlement characteristics of large drilled shafts embedded in bed rocks. Generally, the settlement of large drilled shafts embedded in bed rocks is too small to determine the ultimated load with application of the regulation in design code for either the total settlement or the residual settlement. Therefore, to determine the yield load of large drilled shafts embedded in bed rocks, p(load)-logS (settlement) curve method, which has been proposed originally for the driven pile, was applied to the investigation on the data of the pile load tests. This technique shows that the yield load can be determined accurately and easily rather than other conventional techniques such as P-S, logp-logS, S-logt, and P-S curve methods. An empirical equation is proposed to represent the relationship between pile load and settlement before the yield loading condition. And the settlement of piles was related with the depth embedded in rock as well as rock properties. Based on the investigation on the data of pile load tests, the resonable regulations f3r both the total settlement and the residual settlement are proposed to determine the yield load of large drilled shafts embedded in bed rocks.

Experimental Verification of Set-Up Reference Values for the Determination of Downcoiling Tension in Hot Strip Mill (열간압연시 권취장력 설정기준치의 실험적 검증)

  • 공성락;강용기;김영환;문영훈
    • Transactions of Materials Processing
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    • v.10 no.1
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    • pp.53-58
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    • 2001
  • Set-up reference values, used in determining the optimum downcoiling tension, we experimentally verified in this study. During the actual downcoiling, the strip suffers both tension and bending force through the rotation of mandrel. Therefore, simulative test which can measure both tension and bending resistance of strip was performed to estimate set-up reference value for strip tension during downcoiling operations. The values obtained from the simulative test were correlated with the yield stress which has conventionally been used as reference values for downcoiling tension. The correlative analysis showed that the yield stress of strip can be a good reference value for downcoiling tension. Furthermore, the bending load also shows strong correlation with simulated values due to the close relationship between yield stress and bending load.

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