• 한국지반환경공학회 논문집
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• 제9권7호
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• pp.13-23
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• 2008

본 연구에서는 모래다짐말뚝으로 개량된 점성토 지반에 고성토시 발생될 수 있는 측방유동과 교대의 안정성을 파악하기 위하여 원심모형실험과 수치해석을 수행하였다. 원심모형실험과 수치해석은 교대 배면구간을 EPS로 성토한 경우(Case 1)와 토사로 성토한 경우(Case 2)에 대하여 수행하였으며, 모형실험시 교대와 성토체에 potentiometer를 설치하여 교대상부의 수직변위와 수평변위 및 성토체의 수직변위를 측정하였다. 원심모형실험결과 Case 1에서 교대의 수평변위는 1.4cm 정도로 해석결과와 거의 일치하며, 허용기준을 만족하는 것으로 나타났다. 반면, Case 2에서 교대의 수평변위는 12cm 정도로 해석결과에 비해 18% 정도 크게 평가되었으며, 허용기준을 초과하는 것으로 나타났다. 해석결과 Case 1에서 말뚝의 최대수평변위는 1.26cm로 허용 수평변위 기준(1.5cm)을 만족하는 것으로 나타난 반면, Case 2에서 말뚝의 최대 수평변위는 1.005m로 허용기준을 크게 초과하는 것으로 나타났다.

• Earthquakes and Structures
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• 제7권6호
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• pp.1259-1281
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• 2014

This research has been conducted in order to investigate the effects of peak ground velocity (PGV) of near-field earthquakes on base-isolated structures mounted on Single Friction Pendulum (SFP), Double Concave Friction Pendulum (DCFP) and Triple Concave Friction Pendulum (TCFP) bearings. Seismic responses of base-isolated structures subjected to simplified near field pulses including the forward directivity and the fling step pulses are considered in this study. Behaviour of a two dimensional single story structure mounting on SFP, DCFP and TCFP isolators investigated employing a variety range of isolators and the velocity (PGV) of the forward directivity and the fling step pulses as the main variables of the near field earthquakes. The maximum isolator displacement and base shear are selected as main seismic responses. Peak seismic responses of different isolator types are compared to emphasize the efficiency of each one under near field earthquakes. It is demonstrated that rising the PGVs increases the isolator displacement and base shear of structure. The effects of the forward directivity are greater than the fling step pulses. Furthermore, TCFP isolator is more effective to control the near field effects than the other friction pendulum isolators are. This efficiency is more significant in pulses with longer period and greater PGVs.

• 대한치과보철학회지
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• 제37권6호
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• pp.791-799
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• 1999

The purpose of this study was to investigate the displacements of cast framework by torch soldering and electric soldering techniques. Specimen had two cylinders and connecting bar that had sectioned with 0.3mm gap at mid point. 10 of total specimens were divided into two groups. In torch soldered group, soldering investment block was made and conventional torch solder-ing procedure was carried out. In electric soldered group, electric soldering was carried out on the master cast without soldering investment block by using electric soldering machine(Dentapunkt DP 7, Kulzer, Germany) After soldering procedure, three dimensional coordinates of two centroids of each cylinder were measured by three dimensional coordinate measuring machine. The intercentroidal displacement and global displacement were calculated and then, these values were compared and evaluated. The results were obtained as follows: 1. Intercentroidal distances of specimens decreased after both soldering procedures, and the decrease in intercentroidal distance was greater for torch soldered group than for electric soldered group 2. Global displacements of torch soldered group were greater than those of electric soldered group.

• 한국안전학회지
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• 제20권3호
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• pp.152-157
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• 2005

This experimental study was devoted to investigate skin friction of H group piles with uplift loading conditions in granite soil under laboratory test. Model piles made of steel embedded in weathered granite soil were used in this study. Pile arrangements($2{\times}2,\;3{\times}3$), pile space(2D, 4D, 6D), and soil density($D_r=40%,\;80%$) were tested. The main results obtained from the model tests can be summarized as follows. The series of tests found that ultimate uplift load and displacement for group piles were increased as piles space ratio increases to $D_r=40%$ of soil density. In the relative density of $D_r=80%$, bearing capacity for group piles was greater than for single pile. In the relative density of $D_r=40%$, the theoretical value of skin friction for group piles was greater than practical value. In the relative density of $D_r=80%$, both theoretical and practical value of skin friction for group piles were increased as piles space ratio increases.

• Ocean Systems Engineering
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• 제13권1호
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• pp.57-77
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• 2023

In the present study, the total hydrodynamic pressure exerted by the fluid on walls of rectangular tanks due to horizontal excitations of different frequencies, is investigated by pressure based finite element method. Fluid within the tanks is invisid, compressible and its motion is considered to be irrotational and it is simulated by two dimensional eight-node isoparametric. The walls of the tanks are assumed to be rigid. The total hydrodynamic pressure increases with the increase of exciting frequency and has maximum value when the exciting frequency is equal to the fundamental frequency. However, the hydrodynamic pressure has decreasing trend for the frequency greater than the fundamental frequency. Hydrodynamic pressure at the free surface is independent to the height of fluid. However, the pressure at base and mid height of vertical wall depends on height of fluid. At these two locations, the hydrodynamic pressure decreases with the increase of fluid depth. The depth of undisturbed fluid near the base increases with the increase of depth of fluid when it is excited with fundamental frequency of fluid. The sloshing of fluid with in the tank increases with the increase of exciting frequency and has maximum value when the exciting frequency is equal to the fundamental frequency of liquid. However, this vertical displacement is quite less when the exciting frequency is greater than the fundamental frequency.

• 한국산학기술학회논문지
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• 제12권10호
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• pp.4642-4647
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• 2011

평면 변형률 상태에 있는 탄성지반의 해를 변분법을 적용하여 유도하여 보았다. 변분법 적용시 종방향 변위분포 함수는 선형함수를 고려하였다. 탄성지반상에 작용하는 하중조건은 집중하중과 분포하중을 고려하였는데 집중하중 작용시 탄성지반의 종방향 변위분포양상은 하중 작용점에서 멀어질수록 변위가 급격하게 감소하는 양상을 나타내었다. 등분포하중 작용시 지표면 변위는 압축층 두께에 대한 재하폭의 반의 비(B/H)값이 클수록 하중재하부분 아래에서 보다 균등하게 발생하였다. 또한 하중재하부분을 벗어난 영역에서는 B/H 값이 커질수록 하중재하 모서리 부분으로부터 짧은 거리에서 변위가 0에 수렴하였다.

• 치과방사선
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• 제9권1호
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• pp.13-18
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• 1979

The purpose of this study was to investigate the radiographic images of Temporomandibular joint trouble patients. This study included 186 patients with the chief complaints of TMJ pain and dysfunction. Their age ranged from 17 to 68 years. All patients were identified in the department of Dental mary of College of Dentistry, Seoul National University, Apr. 1978 to Jun. 1979. The author has observed the radiographic variations of two positions of condylar head taken by modified transcranial oblique-lateral projection, which are one in centric occlusion and the other in 1 inch(2.54㎝) mouth open. The results were obtained as follows; 1. In centric occlusion, the distances and positional relationship between the summit of condylar head and the deepest point of articular fossa revealed more or less large variations; Normal range is of 37.9%, anterior displacement of 37.3% and posterior displacement of 22.6%. 2. In the horizontal movement of condylar heads when on 1 inch mouth open, it was revealed that normalrange was of 46.5%, anterior displacement of 12.3%, posterior displacement of 41. 1 %. 3. In the positional interrelationship of both condylar heads when on 1 inch mouth open, it was revealed that symmetry(71. 5%) occurred approximately 2.5 times as many as asymmetry. 4. In both centric occlusion and 1 inch mouth open, it was showed that almost all estimated figures were greater in male than in female, and in the horizontal movement of condylar head when on 1 inch open, it was showed that hypermobility was dominant in male and hypomobility in female.

• Journal of Oral Medicine and Pain
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• 제16권1호
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• pp.33-72
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• 1991

The purpose of this study was to investigate the stress distribution and the displacement in the temporomandibular joints following the teeth loss patterns. The three dimensional finite element method was used for a mathematical model. The finite element model was composed of 1,632 elements and 2,411 nodes in the mandible with articular disc and mandibular fossa of the temporal bone. The masseter, the temporal and the internal pterygoid muscle forces were applied at each insertion site, bisecting point of gonion and antegonion, tip of the coronoid process, and gonion at the ration of 2:2:1 respectively. The directions of muscles force were obtained from frontal and lateral cephalometric tracings using bony landmarks of the skull. The results were as follows : 1. In control model, the minimum principal stresses were concentrated on the region of anterosuperior part of the condyle head and articular disc, and maximum principal stresses on the anterior part of the condyle head and posterolateral part of the articular disc. 2. In case of unilateral teeth loss, the greater principal stress appeared at the teeth loss side and the principal stresses increased at the teeth loss side as the number of the posterior teeth loss went up. 3. In case of bilateral teeth loss, the principal stresses were greater than those of the control model and as the number of the posterior teeth loss increased, the grater principal stresses on the temporomandibular joints appeared at the both side. 4. When the posterior teeth existed bilateral, the principal stress patterns were similar to those of the control model. 5. The displacement ws directed mainly upward and backward in the upper part of the temporomandibular joints and upward and forward in the largest part of the condyle head. The displacement increased as the number of the posterior teeth loss went up.

• 대한치과보철학회지
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• 제37권3호
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• pp.358-374
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• 1999

This study measured the relative displacements of the five-unit fixed partial dentures as cast with the same fixed partial dentures sectioned and assembled by investment-soldering, solder-ing stand-soldering, and cast-joining techniques A total of fifteen specimens using a type IV gold alloy were one-piece cast as control and then sectioned and assembled five test specimens for each method were prepared. A computerized three dimensional coordinate measuring machine and specially designed cylinder for this study were used. Displacement was defined by six displacement variables for the each of cylinders incorporated in each casting: three component displacements(${\Delta}Lx,\;{\Delta}Ly,\;and\;{\Delta}Lz$) and rotational displacements(${\Delta}{\theta}x,\;{\Delta}{\theta}y,\;{\Delta}{\theta}z$). The global displacement was computed using the mathematical formula ${\Delta}R$ = Global displacement =$\sqrt{{(x'-x)}^2+{(y'-y)}^2+{(z'-z)}^2}$ Under the conditions of this study, the following conclusions were drawn: 1. The investment-soldering group showed the largest mean value of final global displacements, followed by stand-soldering group, cast-joining group and one-piece cast group. However, between the mean values of final global displacement for the cast-joining group and one-piece cast group, there was no significant difference. 2. For investment-soldering and stand-soldering groups, the greater global displacements were recorded in soldering phase than in indexing or investing phase. 3. For one-piece cast group, the displacements occured mostly in the casting phase. And for cast-joining group, there was no significant difference in global displacements among the fabricating procedures. 4. Intercentroidal distance decreased in framework-patterning, solder-indexing, solder-standing, and soldering phases, but increased in investment block-investing and casting phases. 5 Specially designed cylinder for touch-trigger type coordinate measuring machine was validated.

• 한국지반신소재학회논문집
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• 제10권4호
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• pp.1-10
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• 2011

측방유동의 발생이 가능한 해안연약지반에 성토를 시행하면 지표면의 하부에는 수평변위가 발생한다. 이러한 수평변위는 인접지반에 변형을 발생하여 인접 지하에 매설된 각종 기반시설에 영향을 미칠수 있다. 수평변위의 억지대책으로 성토지지말뚝과 억지말뚝을 적용하였고, 억지대책의 효과분석을 위해 무보강지반과 보강지반으로 구분하여 수치해석을 시행하였다. 수치해석 결과는 억지말뚝 보강시가 무보강시보다 1.9배의 효과가 있었다. 성토지지말뚝의 보강은 무보강시보다 2.6배의 효과가 있는 것으로 나타났다. 또한, 두 억지대책중 억지말뚝 보강보다 성토지지말뚝 보강이 1.3~1.6배의 효과가 있는 것으로 나타났다.