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Analysis of Piled Raft Bearing Capacity Increase with Centrifuge Test (원심모형시험을 통한 Piled Raft 기초의 지지력증가 특성 분석)

  • Park, Dong-Gyu;Choi, Kyu-Jin;Kim, Dong-Wook;Chung, Moon-Kyung;Lee, Jun-Hwan
    • Journal of the Korean Geotechnical Society
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    • v.28 no.8
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    • pp.43-53
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    • 2012
  • In the conventional design of a piled raft, the axial resistance offered by the raft itself is typically neglected and only that of the group pile is accounted in estimating the total axial resistance of the piled raft. As a consequence, piled rafts are usually designed conservatively by neglecting the raft resistance. In this study, a series of centrifuge model tests have been performed to compare the axial behavior of a group pile with that of a piled raft (both having 16 component piles with an array of $4{\times}4$) in sands with different relative densities and in clays with different preconsolidated pressures. The test results revealed that, with respect to the allowable settlement of 25 millimeters for bridge foundations, the piled raft resistances were greater than those of the group pile by 13% for dense sand, by 22% for loose sand, by 30% for stiff clay, and by 22% for soft clay. Furthermore, the ratio of piled raft resistance to group pile resistance increased as the settlement increased.

A study on a reasonable modeling method of fully grouted rockbolt (전면접착형 록볼트의 거동 특성을 고려한 합리적인 모델링 방법에 대한 연구)

  • Hong-Joo Lee;Kyung-Nam Kang;Ki-Il Song;Sang-Don Lee
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.26 no.1
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    • pp.19-37
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    • 2024
  • Rockbolts are the primary-supports in NATM tunnels and are widely used at tunnel construction sites. Among the rockbolts methods applied in domestic tunnel design, fully grouted rockbolts are the most representative and frequently used. Fully grouted rockbolts exhibit relative behavior between the bolt and the ground due to the grout material. However, during numerical analysis for tunnel design, fully grouted rockbolts are often modeled in a way that does not reflect their behavior characteristics. This may result in underestimating or overestimating the force of the supports. Based on a literature review, it was analyzed that fully grouted rockbolts are modeled using truss element or cable element. To analyze the effect of grout properties of cable elements on rockbolts behavior, this paper compared the behavior of rockbolts in two models: one estimating grout properties based on rockbolt pull-out test data, and another assuming complete adhesion between the rockbolts and the ground by applying large grout properties. Under identical tunnel conditions, the numerical analysis was conducted by modeling the fully grouted rockbolts differently using truss and cable elements, and the tunnel behavior was analyzed. The research results suggest that modeling fully grouted rockbolts as a function of the interface effect between the bolts and the ground, specifically considering grout, is desirable. The use of pull-out test data to simulate the behavior of actual fully grouted rockbolts was considered as a valid approach.

Stability Evaluation of Green Wall System due to Facing Rigidity (전면벽체 강성에 따른 그린월 시스템의 안정성 평가)

  • Park, Si-Sam;Kim, Hong-Taek;Kim, Seung-Wook;Kim, Yong-Eon
    • Journal of the Korean Geosynthetics Society
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    • v.5 no.3
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    • pp.9-15
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    • 2006
  • The Green Wall system is one of segmental concrete crib type earth retaining wall. Green wall is constructed as procedures that lay the front stretchers, rear stretchers and headers then making a rigid body through harden filled soil of interior cell. Recently, Green Wall method is applied in variable cutting ground construction because of advantage which minimize to cut base ground. In case of Green Wall method is constructed with soil nail method, expect that total system stability will increase more than flexible facing because of facing stiffness is big. However, in this case of design, facing stiffness is not considered so that is poor economy. Hence, in this study, stability increasing effect of total system analyze about that soil nail method is constructed with rigidity facing like a Green Wall method. In present study, laboratory model tests was performed for analysis on stability increasing effect of total system about changing stiffness of facing. LEM analysis conducted for evaluation on safety factor of total system sliding that facing condition changed.

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Field Performance of Reinforced Earth Wall with Steel Framed-Facing (강재틀 보강토옹벽에 대한 현장 시험시공)

  • Lee, Kwang-Wu;Cho, Sam-Deok;Kim, Ju-Hyong;Seo, Chang-Won
    • Journal of the Korean Geosynthetics Society
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    • v.6 no.4
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    • pp.39-48
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    • 2007
  • This paper introduces a recently developed reinforced earth wall system with steel framed-facing. The new system incorporates a steel-framed facing that might be assembled on-site and steel strip or geogrid type reinforcements for backfill area. In order to enhance scenery view design of the wall construction, dual-structured facing is proposed in which room for planting space locates in the front of facing. A reinforced earth walls using the proposed system was constructed to verify constructability of the proposed system and facing movement and tensile characteristics of reinforcement were measured to understand the mechanical behavior.

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Cold Spray 증착된 Cu의 전면전극 특성연구

  • Gang, Byeong-Jun;Park, Seong-Eun;Kim, Yeong-Do;Kim, Seong-Tak;Lee, Hae-Seok;Cha, Yu-Hong;Kim, Do-Yeon;Park, Jeong-Jae;Yun, Seok-Gu;Kim, Dong-Hwan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.482.1-482.1
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    • 2014
  • 고효율 셀 및 생산 단가 절감은 결정질 실리콘 태양전지에서 가장 중요시되고 있는 이슈이다. 그 중 박형 실리콘 웨이퍼를 사용하는 공정은 고효율 및 생산단가의 절감을 만족시킬수 있는 방안으로 개발되고 있으며, 전면 전극 재료인 Ag를 다른 금속 재료로 대체하는 방법 또한 단가 절감을 위한 방안으로 연구가 진행 중이다. 하지만 박형 웨이퍼를 기존 공정에 적용할 시 전후면 전극 형성을 위한 고온의 소성 공정 때문에 웨이퍼의 휨 현상이 문제가 되고 있다. Cu 금속 분말의 저온 분사법을 결정질 실리콘 태양전지 전면전극 형성에 적용할 경우, 박형 실리콘 웨이퍼에 적용하는 문제와 Ag 전극의 대체 전극 사용 문제를 동시에 해결할 수 있는 대안이 될 것으로 사료된다. 본 연구에서는 Cold spray법을 사용하여 결정질 실리콘 태양전지 에미터 위에 Cu 전면 전극을 형성하였으며 반복되는 증착 횟수에 따른 전기적 특성 및 형상학적 특성 등을 평가하였다. 전극 형성 전의 Cu 분말 크기는 1~10 마이크론 이었으며, 주사전자현미경을 이용하여 전극의 형상 및 종횡비를 측정하였다. 또한 transfer length method (TLM) 패턴을 실리콘 웨이퍼 표면에 형성하여 접촉 저항 특성 및 전극의 비저항을 평가하였다.

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Electrical and Optical Characteristics of Top-emission OLED (전면 발광 OLED의 전기 광학적 특성)

  • Shin, Eun-Chul;Ahn, Hui-Chul;Han, Won-Geun;Jang, Kyung-Uk;Choi, Seong-Jae;Lee, Ho-Sik;Song, Min-Jong;Kim, Tae-Wan
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.04b
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    • pp.22-23
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    • 2008
  • 본 연구에서는 전면 유기 발광소자(TE-OLED)를 제작하여 전기 광학적 특성을 연구하였다. 전면 발광 OLED의 투명 전극으로 사용된 Al과 Ag의 박막 두께에 따른 투과율과 면저항값은 다음과 같이 나타났다. 파장 520nm의 기준으로 Al 금속 박막의 두께가 10nm 이하여야 50% 투과율을 보였고, 반면 Ag는 25nm 이하로 나타났다. 면저항값은 박막두께 20nm 기준으로 Al은 약 $40\Omega/\square$, Ag는 $10\Omega/\square$이하로 나타났다. 전면발광 방식의 시야각에 따른 빛의 세기는 cos $60^{\circ}$ 일 때 0.1로, TE-OLED는 시야각이 증가하였을 때 현저히 감소되는 것을 볼 수 있다. TE-OLED의 시야각의 증가에 따른 EL-peak 또한 약 520nm의 파장대에서 약 500nm으로 변화하였다. 전면 발광 방식의 반폭치(FWHM)는 배면 발광 방식 보다 약 32nm정도 좁게 나타났다.

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Resisting Behavior of Fully-Grouted Rock Bolts with Compressible Spacers (압축성 간격재를 설치한 전면접착식 볼트의 인발저항 거동)

  • Hwang, Yong-Sub;Lee, Sang-Duk
    • Tunnel and Underground Space
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    • v.21 no.5
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    • pp.377-385
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    • 2011
  • In order to prove the applicability of rock bolts with compressible spacers, laboratory model tests and large scale model tests were conducted. Laboratory model tests were performed in various distance of compressible spacers to determine the optimal distance of compressible spacers. The optimal distance of compressible spacers was found that is 1/4 of rock bolts unit length. Large scale model tests that the size was 0.6 m (diameter) ${\times}$ 4.45 m (length) were conducted. Test results showed that pull out resistance could be increased up to 15% larger than that of unused case by using compressible spacers.

Analysis of the Radiation Pattern in Relation to the Head Mass Shape Applicable to a Tonpilz Transducer (Tonpilz 트랜스듀서에 적용 가능한 전면추 형상에 따른 방사 패턴 해석)

  • Kim, Hoe-Yong;Roh, Yong-Rae
    • The Journal of the Acoustical Society of Korea
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    • v.29 no.7
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    • pp.422-430
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    • 2010
  • The radiation property of a Tonpilz transducer is influenced by the structural variables of the transducer. In this study, with respect to a single mode Tonpilz transducer, the radiation patterns were calculated for different head mass geometries of the same effective radiation area. The shapes of the head mass analyzed were the most popular circular, regular triangular, square, regular hexagonal and regular octagonal types, and radiation pattern equations were derived for each of the head mass shapes. Based on the derived equations, radiation patterns in accordance with the shape and size of the head mass were calculated and the results were compared with each other. Validity of the calculation results were confirmed by means of finite element analysis.

High Availability Web Server Cluster for Middle Web Sites (중소형 사이트를 위한 고가용성 웹 서버 클러스터)

  • 문종배;김명호
    • Proceedings of the Korean Information Science Society Conference
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    • 2002.04a
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    • pp.634-636
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    • 2002
  • 최근에 리눅스 가상 서버 프로젝트를 이용한 클러스터를 많이 구축하고 있다. 리눅스 가상 서버는 확장성이 뛰어날 뿐만 아니라 성능도 뛰어나다. 그러나 하나의 전면 서버가 사용자 요청을 받아서 후면 서버가 처리를 하여 사용자에게 응답을 보내는 구조이므로 하나의 전면 서버는 사용자 요청의 급격한 증가로 병목현상을 일으킬 수 있고, 이 때문에 다수의 후면 서버가 있음에도 불구하고 서비스를 할수 없는 상황이 발생하게 된다. 따라서 본 논문에서는 다수의 전면 서버를 두어 병목현상을 근본적으로 없애는 방법을 제안하였다. 모든 클러스터 노드들은 전면 서버와 후면 서버의 역할을 모두 할 수 있도록 하였고 부하량이 많지 않으면 자기 노드에서 직접 처리를 하여 사용자에게 웅답할 수 있도록 하고, 부하량이 많을 때에만 클러스터의 다른 노드들 중 부하가 가장 작은 노드를 선택하여 사용자 요청을 처리할 수 있도록 하였다. 그리고 클러스터 노드들의 부하량을 고려한 스케줄링 알고리즘을 개발하여 좀 더 효율적인 부하 분배방식을 제안하였다.

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