• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.160-165
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• 1998

A theoretical analysis has been undertaken to show the influence of bearing geometry on the steady state characteristics of air lubricated spherical tilting pad bearings. The geometry variations considered are the number of pads, the eccentricity ratio, the direction of load, and the preloading.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.457-467
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• 2010

The settlement prediction is very important to preloading method for a construction site on a soft ground. At the design stage, however, it is hard to predict the settlement exactly due to limitations of the site survey. Most of the settlement prediction is performed by a regression settlement curve based on the field data during a construction. In Korea, hyperbolic method has been most commonly used to align the settlement curve with the field data, because of its simplicity and many application cases. The results from hyperbolic method, however, may be differed by data selections or data fitting methods. In this study, the analyses using hyperbolic method were performed about the field data of $\bigcirc\bigcirc$ site in Pusan. Two data fitting methods, using an axis transformation or an alternative method, were applied with the various data group. If data was used only after the ground water level being stabilized, fitting results using both methods were in good agreement with the measured data. Without the information about the ground water level, the alternative method gives better results with the field data than the method using an axis transformation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.135-136
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• 2006

A precise linear motion stage supported by magnetically preloaded air bearings is introduced where preloading magnetic actuators are combined with permanent magnets and coils to adjust air bearing clearance by controlling magnetic force actively. Each of the magnetic actuators has a permanent magnet generating nominal magnetic flux for required preload and a coil to perturb the magnetic force resulting adjustment of air-bearing clearance. The characteristics of porous aerostatic bearing are analyzed by numerical analysis, and analytic magnetic circuit model is driven for magnetic actuator to calculate nominal preload and variation of force due to current. A 1-axis linear stage motorized with a coreless linear motor and a linear encoder is built for verifying this design concept. With the active magnetic preloading actuators controlled with DSP board and PWM power amplifiers, the active on-line adjusting tests about the vertical, pitching and rolling motion were performed, and the result shows very good linearity.

• 한국생산제조학회지
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• 제18권4호
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• pp.337-347
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• 2009

Generally, finite element models used in structural analysis have some uncertainties of the geometric dimensions, applied loads and boundary conditions, as well as in material properties due to the manufacturability of aluminum intensive body. Therefore, it is very important to refine or update a finite element model by correlating it with dynamic and static tests. The structural optimization problems of automotive body are considered for mechanical structures with initial stiffness due to preloading and in operation condition or manufacturing. As the mean compliance and deflection under preloading are chosen as the objective function and constraints, their sensitivities must be derived. The optimization problem is iteratively solved by a sequential convex approximation method in the commercial software. The design variables are corrected by the strain energy scale factor in the element levels. This paper presents an updated method based on the sensitivities of structural responses and the residual error vectors between experimental and simulation models.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.3-10
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• 2002

Recently, arches are used structurally because of their high in-plane stiffness and strength, which result from their ability to transmit most of the applied loading by axial forces actions, so that the bending actions are reduced. On the other hand, the resistances of arches to (out-of-plane,) flexural-torsional behavior depend on the rigidities EI/sub y/, for lateral bending, GJ for Uniform torsion, and EI/sub w/ for warping torsion which are related to axial stress for flexural-torsional behavior. The resistance of an arch to out-of-plane behavior may be reduced by its in-plane curvature, and so it may require significant lateral bracing. Thus. it is supposed that In-plane preloading which cause an axial stress, have an effect on out-of-plane free vibration behavior of arches. Because axial stresses caused increase or decrease out-of-plane stiffness. But study about this substance is insufficient. In this thesis, We will study an effect of preloading on lateral free vibration of arches, using finite element method based on Kang and Yoo's curved beam theory (about curved beam element have 7 degree of freedom including warping) with FORTRAN programming.

• Geomechanics and Engineering
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• 제28권2호
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• pp.157-169
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• 2022

Preloading of soft clays is a common ground stabilization method for improvement of compressibility and the undrained shear strength. The waiting period under preload is a primary design criterion controlling the degree of improvement obtained. Upon unloading the overconsolidation attained with respect to actual loads defines the long term performance. This paper presents a laboratory study for investigation of creep behavior of Famagusta Bay alluvial soft soil preloaded under various effective stresses for analysis of long term performance based on the degree of overconsolidation. Traditional one-dimensional consolidation tests as well as modified creep tests are performed on reconstituted soft specimens. Compressibility parameters are precisely backcalculated using one dimensional consolidation theory and the coefficient of creep is determined using the traditional Cassagrande method as well as two modified methods based on log cycles of time and the inflection of the creep curve. The test results indicated that the long term creep can be successfully predicted considering the proposed method. The creep coefficients derived as part of this method can also be related to the recompression index (recompression index, swelling index) considering the results of the testing method adopted in this study.

• 지질공학
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• 제32권4호
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• pp.513-523
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• 2022

Preloading을 통한 연약지반처리를 할 때 침하관리는 침하량을 구하고 압밀의 진행상황을 확인하여 이를 실측침하량과 비교·분석하여 preloading의 방치기간, 철거시기, 여성토의 결정 등을 확인하는 것을 목적으로 한다. 침하관리를 위해서는 침하량을 예측해야 하는데 실측 data를 기반으로 침하량을 예측하는 방법 중 쌍곡선법을 이용하여 단계성토로 인한 creep 거동을 고려한 연약지반 침하거동해석을 실시하였다. 기존의 쌍곡선법은 단계성토를 통한 연약지반처리 시 최종침하구간의 data만을 통해 침하량을 예측하였으나, 본 논문에서는 각 단계성토의 침하거동을 해석하고 단계성토에 따른 creep 거동 및 초기탄성침하를 고려하여 압밀거동계수(k)를 제시 및 최종압밀침하량을 예측하였다. 단계성토의 침하거동을 고려한 최종압밀침하량 예측결과, 기존의 최종침하구간의 data만 고려하여 예측한 최종압밀침하량(S_r = 1.05 cm)보다 각 단계성토별 𝛼, 𝛽값을 통하여 예측한 최종압밀침하량(S_r = 0.50 cm)이 더 정확한 값을 예측하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.1169-1174
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• 2001

In this study, the behavior of deteriorated concrete columns under sea-water before and after strengthening with glass fiber composite and the change of behavior by the deterioration of strengthening material are analyzed. In the analysis, the characteristics of concrete deteriorated in sea-water, preloading effect, and corrosion of steel are considered. The result of analysis is verified by the comparison with the experimental data. Using constitutive equations of the concrete and corroded steel, load-moment interaction curves of both deteriorated and strengthened concrete column are derived.

• Tribology and Lubricants
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• 제17권2호
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• pp.116-123
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• 2001

A theoretical analysis has been undertaken to show the influence of bearing geometry on the steady state characteristics of air lubricated spherical tilting pad bearings. The geometry variations considered are the number of pads, the eccentricity ratio, the direction of load, and the preloading. Dynamic characteristic equations are derived with pad assembly method.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 토목섬유기술위원회 학술세미나 논문집
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• pp.33-44
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• 2001

The generally known vertical drain methods for improvement of soft ground are Sand Drain, Sand Compaction Pile, Plastic Drain Board, and Pack Drain. Recently, Plastic Drain Board method application in soft ground is widely used. In this case study, it is compared with each other vertical drain methods from the results of monitorning and test embankment. The results of the analysis and the study show that Plastic Drain Board method is relatively acceptable as vertical drain method.