• Geomechanics and Engineering
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• 제23권6호
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• pp.523-533
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• 2020

The current study focuses on the effect of the end shape of steel pipe piles on installation effort and bearing resistance using the pressing method of installation under dense ground conditions. The effect of pile rotation on the installation effort and bearing resistance is also investigated. The model steel piles with a flat end, cone end and cutting-edge end were used in this study. The test results indicated that cone end pile with the pressing method of installation required the least installation effort (load) and showed higher ultimate resistance than flat and cutting-edge end piles. However, pressing and rotation during cutting-edge end pile installation considerably reduces the installation effort (load and torque) if pile penetration in one rotation equal to the cutting-edge depth. Inclusion of rotation during pile installation reduces the ultimate bearing resistance. However, if penetration of the cutting-edge end pile equal to the cutting-edge depth in one rotation, the reduction in ultimate resistance can be minimized. In comparing the cone and cutting-edge end piles installed with pressing and rotation, the least installation effort is observed in the cutting-edge end pile installed with penetration rate equal to the cutting-edge depth per rotation.

• Geomechanics and Engineering
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• 제33권1호
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• pp.91-99
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• 2023

To test the effect of various pile tip shape series of model scale loading tests were carried out on test piles with special pile tips. Special pile tips were made using the 3D printer and were attached to the bottom end of the test pile for loading tests. The pile tips were made to have 30°, 45°, 60° inclined tips, as well as a rounded tip. The main objective of the test was to observe the effect of various pile tip shapes on settlement and penetrability of the pile. Moreover, a numerical model simulating the pile loading test carried out in this study was established and verified based on the loading test results. From this, the stress concentration around the pile tip was investigated. This will allow us to analyze the decrease of stress concentration around the pile tip which is the main cause of the pile tip damage during pile installation. However, modifying the pile tip shape will eventually increase the settlement of the pile. By estimating the degree of increase in pile settlement, the viability and the efficiency of the pile shape modification was judged. In addition, case studies on the effect of different pile tip shape and ground conditions on pile settlement and stress dispersion was conducted.

• Structural Engineering and Mechanics
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• 제71권2호
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• pp.119-129
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• 2019

Optimum shape and length of laterally loaded piles can be obtained with different optimization techniques. In particular, the Fully Stress Design method (FSD) is an optimality condition that allows to obtain the optimum shape of the pile, while the optimum length can be obtained through a transversality condition at the pile lower end. Using this technique, the structure is analysed by finite elements and shaped through the FSD method by contemporarily checking that the transversality condition is satisfied. In this paper it is noted that laterally loaded piles with optimum shape and length have some peculiar characteristics, depending on the type of cross-section, that allow to design them with simple calculations without using finite element analysis. Some examples illustrating the proposed simplified design method of laterally loaded piles with optimum shape and length are introduced.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.444-449
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• 2004

The design modification of bottom guide structures of the instrumented capsule, which is used for the irradiation test in the HANARO reactor, was required because of the trouble of the bottom guide arm's pin during irradiation. The previous structure with 3-pin arms was changed into the cone shape of one body. The specimens of the bottom end cap ring with three different sizes (${\Phi}68/70/72mm$) were designed and manufactured. The out-pile tests for the capsule with previous and new three bottom guide structures were performed in the one-channel flow test facilities. In order to evaluate the compatibility with HANARO and the structural integrity of the capsule, a loading/unloading, a pressure drop, a thermal performance, a vibration, and an endurance test were conducted. From out-pile test results, the capsule with the cone shape bottom guide structures was found to be more stable than the previous structure and the optimized size of the bottom guide structure selected was 70mm in diameter. It is expected that the new bottom guide structures will be applicable to all material and special capsules which will be designed and manufactured for the irradiation tests in the future.

• 한국지반신소재학회논문집
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• 제18권3호
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• pp.69-77
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• 2019

본 논문에서는 테이퍼 마찰말뚝의 자유진동을 평가할 수 있는 해석모델을 제안하였다. 불균질 지반에 설치된 정적 수직하중을 받는 테이퍼 마찰말뚝의 자유진동을 지배하는 미분방정식을 유도하였다. 이 지배방정식을 Runge-Kutta 법을 이용하여 직접 수치적분하였고, 미분방정식의 고유치인 고유진동수는 Regula-Falsi 법을 이용하여 산정하였다. 원통형 말뚝의 고유진동수 계산값은 기존 문헌값과 잘 일치하였다. 수치예를 통해 말뚝의 변단면, 주면마찰력, 단부조건, 수직압축하중 및 지반의 불균질성이 고유진동수와 모드형상에 미치는 영향을 분석하였다.

• 한국소음진동공학회논문집
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• 제20권4호
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• pp.405-413
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• 2010

The vibration characteristics of fully and partially embedded piles with flexibly supported end carrying an eccentric tip mass are investigated. The pile model is based on the Bernoulli-Euler theory and the soil is idealized as a Winkler model for mathematical simplicity. The governing differential equations for the free vibrations of such members are solved numerically using the corresponding boundary conditions. The lowest three natural frequencies and corresponding mode shapes are calculated over a wide range of non-dimensional system parameters: the rotational spring parameter, the relative stiffness, the embedded ratio, the mass ratio, the dimensionless mass moment of inertia, and the tip mass eccentricity.

• 헤리티지:역사와 과학
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• 제51권4호
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• pp.84-107
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• 2018

첨모직은 표면에 짧은 파일이 나타나는 것으로 조선시대 후기에는 첨모직 깔개를 지칭하는 용어로 채담이 사용되었으며, 20세기 초에는 융전과 단통, 양탄자 등으로 불리었다. 조선 말기 이후의 여러 문헌이나 신문기사, 그리고 각종 사진자료를 통해 첨모직 깔개가 왕실뿐만 아니라 일반인도 사용하였고 당시 국내에서 제작하였다는 것이 확인되었다. 본 연구에서는 조선 말기 이후의 첨모직 깔개 6점을 실물 조사하였는데 5점은 페르시아매듭의 컷파일이며 1점은 루프파일의 기법으로 제작되었다. 컷파일의 깔개는 크기가 가로 72~98 ${\times}$ 세로 150~156cm의 직사각형이며, 나비, 사슴, 호랑이, 그리고 십장생 등의 주 무늬를 중앙에 배치하고 卍자를 가장자리에 배치하였다. 컷파일의 소재는 지경사는 모두 면사이며 지위사는 3점은 면사, 1점은 모사, 그리고 1점은 면사와 비스코스레이온의 혼섬사이다. 지위사는 4점이 S꼬임의 실 여러 올을 합쳐 Z방향으로 합사한 실을 사용했다. 파일위사는 4~6가지의 색이 사용되었는데 홍색을 제외하고 모두 염색을 하지 않은 자연색 그대로의 모섬유가 사용되었다. 그리고 S나 Z꼬임의 모사를 2올 이상 합하여 반대방향으로 꼬임을 주었는데 굵기에 맞춰 올수를 합하였다. 깔개의 위아래 가장자리는 위사를 6올 이상 넣고 남은 지경사는 몇 올씩을 한데 묶어서 정리하였으며, 좌우 가장자리는 3올 이상의 면사를 가운데 놓고 수평으로 감아 마치 둥근 막대처럼 만들며, 가장자리에서 2~3번째 지경사를 징거서 튼튼하게 고정하였다. 루프파일은 경사방향으로 고리를 만든 경첨모직이며 지경사와 지위사는 면사, 파일경사는 모사로 추정된다. 소재의 성분 분석이 가능했던 깔개는 3점으로 파일위사는 판단이 불명한 것을 제외하고 염소와 비미종 양으로 판명되어 첨모직 깔개에 다양한 종류의 동물털이 사용되었을 가능성이 있다고 본다. 본 연구에서 조사한 6점의 깔개는 1800년대 말부터 1900년대 초에 제작되었다고 추정된다. 깔개의 정확한 제작지는 확인할 수 없었으나 당시 국내에서 첨모직 깔개를 제작하고 있다는 문헌기록과 깔개의 문양의 조형성을 고려한다면 우리나라에서 제작된 것으로 본다.