모래지반에서 횡방향 반복하중을 받는 말뚝의 영구수평변위 평가

백성하,김준영,이승환,정충기 한국지반공학회 2017 한국지반공학회논문집 Vol.33 No.2

Pile foundations that support offshore structures or transmission towers are dominantly subjected to cyclic lateral loadsdue to wind and waves, causing permanent displacement which can severely affect stability of the structures. In thisstudy, a series of cyclic lateral load tests were conducted on a pre-installed aluminum flexible pile in sandy soil withthree different relative densities (40%, 70% and 90%) in order to evaluate the permanent displacement of a cyclic laterallyloaded pile. Test results showed that the cyclic lateral loads accumulated the irreversible lateral displacement, so-calledpermanent 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 displacementof a pile increased with decrement of relative density and decreased by soil saturation. From the test results, the normalizedpermanent displacement defined as the cumulative permanent displacement to the initial permanent displacement ratiowas investigated, and empirical equations for predicting the normalized permanent displacement was developed in termsof relative density of the soil and the number of cyclic lateral load.

Top-Down 공법이 적용된 지중연속벽의 설계시 측방토압의 적합성 평가

홍원표(Hong Won-Pyo),강철중(Kang Chul-Joong),윤중만(Yun Jung-Mann) 한국토목섬유학회 2012 한국지반신소재학회 논문집 Vol.11 No.1

본 연구에서는 지중연속벽 설계시 사용되는 범용 해석프로그램에 Rankin(1857)의 이론토압과 홍원표와 윤중만(1995a)의 경험 토압을 각각 적용하여 Top-Down 공법에 적용된 지중연속벽의 수평변위를 분석하였다. 그리고 이들 해석 프로그램에서 산정된 예측변위량과 지중경사계로 측정된 실측변위량을 비교 검토하였다. 현재 지중연속벽 설계에 적용되는 해석프로그램에는 Rankine의 토압이 주로 적용되고 있다. 검토결과, 지중연속벽의 예측수평변위는 적용되는 토압에 따라 상당히 큰 차이를 나타내고 있다. Rankine의 토압을 적용하여 산정된 예측수평변위 형상은 실측결과와 큰 차이를 보이고 있으며 벽체의 하부에서 예측치가 실측치보다 과다하게 산정되었다. 반면, 홍원표·윤중만의 토압을 적용하여 얻은 예측수평변위 형상과 최대수평변위 량은 실측결과와 유사하게 나타났다. 따라서 Top-Down 공법이 적용된 지중연속벽의 설계시 Rankine의 토압보다는 홍원표·윤중만의 경험토압을 적용하는 것이 적합함을 알 수 있다. The Rankine(1857)'s earth pressure and the Hong and Yun(1995a)'s earth pressure was applied to analyze the lateral displacement of diaphragm wall applied to the Top-Down construction method using the computer program, which is a common design program for diaphragm wall. The lateral displacement estimated by the computer program was compared with the lateral displacement measured by inclinometer. The Rankine's earth pressure has been widely used to design the diaphragm wall in the analysis of computer program. As the result of comparison, the lateral displacement of diaphragm wall was predicted differently according to the applied earth pressures. The behavior of lateral displacement predicted by the Rankine's earth pressure was different with displacement measured by inclinometer and the lateral displacement at the bottom part was overestimated. However, the lateral displacement predicted by the Hong and Yun's earth pressure is similar to the behavior and maximum value of real displacement. Therefore, the Hong and Yun's earth pressure is more suitable than the Rankine' earth pressure to design the diaphragm walls applied to the Top-Down Construction Method.

Y자형 무량판 구조시스템 아파트의 코어 면적 비율에 따른 횡력 저항 성능 비교분석

박천석,안재혁 대한건축학회지회연합회 2014 대한건축학회연합논문집 Vol.16 No.4

본 연구에서는 정방형 평면 형태를 대상으로 한 기존연구를 토대로 Y자형 무량판 구조시스템 아파트의 코어면적에 따른 횡력 저항 성능을 분석하기 위해 코어면적 비율의 변화에 따른 구조해석을 실시하여 코어면적 비율이 횡변위 제어에 미치는 영향을 분석하고 평면 형태에 따라 코어 면적 비율이 횡력 저항 성능에 미치는 영향을 파악하기 위해 9%에서 18%까지 코어면적 비율을 다양하게 변화시켜 구조해석을 실시하여 해석결과에 따른 최상층 횡변위를 비교하여 코어면적 비율에 따른 횡력 저항 성능을 검토한다. 또한 건축물의 높이에 따라 코어면적이 횡력 저항 성능에 미치는 영향의 차이도 함께 검토하고 기본연구에서 제시한 결과를 토대로 평면 형태별로 코어면적 비율과 구조적 안전성과의 관계를 파악한다. The purpose of this study is to analyze lateral load resisting capacity by core area ratio of y type floor plan apartment with flat plate system and to find an effective core ratio to control lateral displacement of y type floor plan apartment with flat plate system. In y type floor plan apartment with flat plate system, the core wall has an important role of controlling lateral displacement. When the spacious core area is good for controlling lateral displacement, but residential area will become small. Contrary, small core area has disadvantage in lateral displacement, but residential area will become more spacious. This study uses analysis program, Midas Gen. Core area ratio is five, from 9% to 18%. As a result, when the core area ratio is 18%, lateral displacement is declined 45% than lateral displacement when the core area ratio is 9%. The difference of lateral displacement decrement in the top floor occurred according to raising core area ratio. The lateral displacement decrement is 38%~17% when core area ratio is 13% or under, but it is 20%~13% when core area ratio is 13% or more.

Immediate effects of mandibular posterior displacement on the pharyngeal airway space: A preliminary study

Yeonju Choi,Yong-Il Kim,Seong-Sik Kim,Soo-Byung Park,Woo-Sung Son,김성훈 대한치과교정학회 2020 대한치과교정학회지 Vol.50 No.2

Objective: This study aimed to evaluate the immediate effects of mandibular posterior displacement on the pharyngeal airway space (PAS) by using cephalometric evaluations and to investigate how the surrounding structures are schematically involved. Methods: In this retrospective study, 38 subjects with functional Class III malocclusion and two lateral cephalograms were selected. The first lateral cephalogram was taken with the mandible in the habitual occlusal position, and the second in anterior edge-to-edge bite. Paired t -test was used to analyze changes in the PAS, hyoid bone, tongue, and soft palate, followed by mandibular posterior displacement. Pearson’s correlation analysis was used to determine the relationship between the amount of mandibular posterior displacement and other variables. Results: A statistically significant decrease was observed in the PAS following mandibular posterior displacement. Along with mandibular posterior displacement, the tongue decreased in length (p < 0.001) and increased in height (p < 0.05), while the soft palate increased in length, decreased in thickness, and was posteriorly displaced (p < 0.001). The hyoid bone was also posteriorly displaced (p < 0.05). There was no correlation between the amount of mandibular posterior displacement and the measured variables. Conclusions: The PAS showed a statistically significant decrease following mandibular posterior displacement, which was a consequence of retraction of the surrounding structures. However, there were individual variances between the amount of mandibular posterior displacement and the measured variables. [Korean J Orthod 2020;50(2):129-135]

사질토 지반에서 수평하중에 따른 단일강관말뚝의 거동특성에 관한 실험적 연구

김대현(Kim, Daehyeon),이태광(Lee, Tae-Gwang),김선학(Kim, Sun-Hak) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.5

해상풍력기초를 설계함에 있어 사용하중에 대해 극한적인 조건뿐만 아니라 지속적인 동적하중에 대해 기초의 거동을 정확하게 파악하여 안정적이고 경제적인 기초를 개발할 필요성이 있다. 이를 위하여 강관말뚝을 일정비율로 축소시켜 모형 말뚝을 제작하고, 모형토조에 모래층을 500mm의 높이로 포설한 후 모형말뚝을 모델링하여 정적 및 반복 수평재하실험을 실시하였다. 그 결과, 정적수평재하시 모형말뚝의 길이/직경(L/D)이 클수록 하중에 따른 변위는 증가하는 반면, 반복수평재하 시 하중재하 횟수가 증가할수록 반복수평하중 1회당 발생하는 말뚝의 수평변위는 감소하였고 지반이 조밀할수록 반복수평하 중에 의한 말뚝의 극한수평지지력의 증가율이 작아지는 것으로 나타났다. 또한 휨모멘트의 분포형상은 지반의 상대밀도에 상관없이 유사한 형태를 보였으며, 최대휨모멘트는 지표면으로부터 170mm지점에서 발생하는 것으로 나타났다. 그리고 지반 의 상대밀도가 증가할수록 정적수평재하와 반복수평재하 조건에서 발생하는 최대휨모멘트는 증가했다. 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.

연직배수공법이 적용된 연약지반 상에 도로성토로 인한 측방유동의 특성

홍원표,김정훈 한국지반공학회 2012 한국지반공학회논문집 Vol.28 No.9

Field monitoring data for embankments in thirteen road construction sites at coastal area of the Korean Peninsula were analyzed to investigate the characteristics of lateral flow in soft grounds, in which vertical drain methods were applied. First of all, the effect of the embankment scale on the lateral flow was investigated. The thicker soft soils and the lager relative embankment scale produced the more horizontal displacements in soft grounds. Especially, if thick soft grounds were placed, the relative embankment scale, which was given by the ratio of thickness of soft ground to the bottom width of embankments, became larger and in turn large horizontal displacement was produced. And also the higher filling velocity of embankments induced the more horizontal displacements in soft grounds. The other major factors effected on the lateral flow in soft ground were the thickness and undrained shear strength of soft grounds,the soil modulus and the stability number. The more maximum horizontal displacement was induced by the less undrained shear strength and soil modulus of soft grounds. Also the more stability number produced the more maximum horizontal displacement. When the shear deformation was not developed, the stability number was less than 3.0 and the safety factor of bearing was more than 1.7. However, if the stability number was more than 5.14 and the safety factor of bearing was less than 1.0, the unstable shear failure was developed in soft ground. 50mm can be recommended as a criterion of the allowable maximum horizontal displacement to prevent the shear deformation in soft ground, while 100mm can be recommended as a criterion of the allowable maximum horizontal displacement to prevent the shear failure in soft ground.

Effects of Axial Prestressing on Lateral Displacement of Steel Pipe Columns

Demapelis,Paul Marion,Tiburcio,Rodelio,Dakila,Michael Erick,Ondo,Jose Carlo,Rubio,Christabel Jane 한국방재학회 2016 Journal of Disaster Management Vol.1 No.4

The application of prestressing to concrete beams has been used to improve flexural strength. With the demand in producing tall, sleek structures (i.e. monopoles), stiffness must be improved, thus decreasing lateral displacement. This study will cover the effects of prestressing steel columns by determining the magnitude of lateral displacement for a given applied axial force. For this study, a 16mm threaded bar was used as the prestressing medium. In the first experiment, the threaded bar was subjected to varying levels of torques. The corresponding axial forces were measured by using spring balances. The aim for the first experiment is to provide a relationship between the applied torque and its corresponding prestressing force. The relationship observed was then used to determine the prestressing force for the second experiment. For the second experiment, a steel column was subjected to horizontal forces by mounting a motor on top of it. It was subjected to varying prestressing forces by using the threaded bar. Lateral displacements were then observed for each force applied. The initial experiment yielded an average ratio of 39.45 N axial force for every 1 N-m applied torque. This ratio was then used to determine the prestressing force applied in the second experiment. It was noted that after subjecting the column to prestressing force, the observed lateral displacement decreased. The results indicated that prestressing steel columns can reduce lateral displacement.

연약지반에 성토시 발생하는 수평변위 억지를 위한 말뚝보강 효과에 대한 수치해석

김재홍(Kim Jae-Hong) 한국토목섬유학회 2011 한국지반신소재학회 논문집 Vol.10 No.4

측방유동의 발생이 가능한 해안연약지반에 성토를 시행하면 지표면의 하부에는 수평변위가 발생한다. 이러한 수평변위는 인접 지반에 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. When an embankment is performed on the soft ground of the coastal with possibilities of lateral flow, lateral displacement occurs to the bottom of the surface of the ground. This lateral displacement can affect existing infra structures that are buried in the adjacent underground by causing a displacement in the nearby base foundation. Soft ground supporting piles and reinforced piles were applied as reinforcement remedies against the lateral displacement. And for the effect analysis, numerical analysis was performed under the classifications of non-reinforcement base and reinforced base. The result of the numerical analysis showed that the reinforced piles had more effects by 1.9 times than non-reinforced piles. Soft ground supporting piles showed better effects by 2.6 times than non-reinforced piles. Additionally, between the two reinforced remedies, soft ground supporting piles showed greater effects by 1.3-1.6 times than the reinforced piles.

The relationship between time-varying eccentricity of load with the corner lateral displacement response of steel structure during an earthquake

Kambiz Takin,Behrokh H. Hashemi,Masoud Nekooei 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.4

In an actual design, none of the structures with shear behaviors will be designed for torsional moments. Any failure or damages to roofs, infills, shear walls, and braces caused by an earthquake, will inevitably result in relocation of center of mass and rigidity of the structure. With these changes, the dynamic characteristics of structure could be changed during an earthquake at any moment. The main objective of this paper is to obtain the relationship between time-varying eccentricity of load and corner lateral displacement. In this study, various methods have been used to determine the structural response for time-varying lateral corner displacement. As will be seen below, some of the structural calculation methods result in a significant deviation from the actual results, although these methods include the interaction effects of modes. Controlling the lateral displacement of structure can be performed in different ways such as, passive dampers, friction dampers, semi-active systems including the MR damper and active Systems. Selecting and locating these control systems is very important to bring the maximum safety with minimum cost into the structure. According to this study will be show the relation between the corner lateral displacements of structure and time-varying eccentricity by different kind of methods during an earthquake. This study will show that the response of the structure at the corners due to an earthquake can be very destructive and because of changing the eccentricity of load, calculating the maximum possible response of system can be carried out by this method. Finally, some kind of systems must be used for controlling these displacements. The results shows that, the CQC, DSC and exact methods is comply each other but the results of Vanmark method is not comfortable for these kind of buildings.

초고층 건물의 초기 설계단계 적용을 위한 간략시공단계 해석기법

양홍민(Yang, Hong-Min),김재요(Kim, Jae-Yo),엄태성(Eom, Tae-Sung),장동운(Jang, Dong-Woon) 대한건축학회 2012 大韓建築學會論文集 : 構造系 Vol.28 No.11

This study suggests the simplified construction sequence analysis scheme which predicts the lateral displacements of reinforced concrete structures under construction, with basic design and construction information in structural design stages. In each construction stage, elastic vertical and lateral displacements due to vertical loads are calculated by using stiffness matrix of the structure, and the inelastic shortening of vertical members due to creep and shrinkage are added. Also, lateral displacements caused by the differential shortening of vertical members are calculated by the equivalent loads from compatibilities of vertical displacements. Total lateral displacement is calculated by a summation of elastic lateral displacements of the structure, horizontal components of the inelastic shortening of vertical members, additional lateral displacements caused by the differential shortening of vertical members, and lateral displacements caused by shrinkage of horizontal members. The the proposed method is verified by applications to a regular-shaped building under symmetric load or asymmetric load, and a complex-shaped building with zoning construction.