• 대한조선학회논문집
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• 제29권2호
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• pp.132-139
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• 1992

기하학적 비선형 해석과정에서 일반적인 방법으로는 연속적인 하중증분단계의 기하학적 변위증분에서 절점회전이 미소하다는 가정에 의해 제한되어 접선강성행렬을 유도하고 유한회전의 영향을 증분평형 방정식의 반복계산하는 과정에서 고려하는 방법이 사용되고 있다. 그리고 개선된 방법으로는 미소회전증분의 가정을 무시하고 유한회전증분의 영향을 고려하여 접선강성행렬을 유도하는 방법이 Surana, Onate 및 Dvorkin 등에 의해서 개발되었다. 유한 회전을 고려하는 방법에서 Surana는 비선형 절점 회전함수를 가정하여 강성메트릭스를 유도하였으며 Onate와 Dvorkin은 전체좌표에서 회전각에 대한 회전행렬의 2차항까지를 고려한 강성메트릭스를 유도하였다. 본 논문에서는 유한요소의 기하학적 위치를 나타내는 변위함수의 방향 벡터를 삼각함수로 표현하여 연속적인 하중증분 사이의 방향벡터 증분을Tayler의 급수로 2차항까지 전개하므로써 비선형 회전 증분을 고려한 쉘 요소를 개발하였다. 기하학적 비선형 해석과정은 연속체 운동의 증분이론을 도입하여 Total Lagrange(T.L.)수식과 Updated Lagrange(U.L.)수식으로 비선형 거동을 해석하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.276-279
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• 1997

When a magnetostrictive material is exposed to a magnetic field, its geometry changes due to a magnetostrictive effect. The magnetostriction is analogous to the piezoeletricity. The displacement of the magnetostrictive material is proportional to the applied current while that of the piezoelectric material is proportional to the voltage. A magnetostrictive material generates large displacement and higher compressive force compared with a piezoeletric material. These advantages provide a good performance of a vibration isolation of a platform. In this work, it is applied to a driving actuator for vibration isolation of a platform. The properties of a magnetostrictive material are investigated in terms of hysteresis and displacement vs. applied current for a various preload. Modeling of the displacement of the vibration isolating actuator is performed as it behaves as a flow source. A sliding mode controller is designed to demonstrate the ability of the magnetostrictive actuator to reduce the vibration at the platform. The effectiveness of the proposed scheme is demonstrated through experimental works. The experimental results of the vibration of the platform axe presented in terms of time response and frequency response.

• Imaging Science in Dentistry
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• 제33권4호
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• pp.211-215
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• 2003

Purpose: To assess the radiographic findings of odontogenic cysts showing displacement of the mandibular canal using computed tomographic (CT) and panoramic images. Materials and Methods : CT and panoramic images of 63 odontogenic cysts (27 dentigerous, 16 odontogenic keratocysts, and 20 radicular cysts) were analyzed to evaluate the following parameters: the dimension and shape of the cysts, and the effect of the cysts on the mandibular canal and cortical plates. Results: Of the 63 cysts examined in the study, 35 (55.6%) showed inferior displacement of the mandibular canal and 46 (73.0%) showed perforation of the canal. There were statistically significant differences between CT and panoramic images in depicting displacement and perforation of the mandibular canal. Cortical expansion was seen in 46 cases (73.0%) and cortical perforation in 23 cases (36.5%). The radicular cysts showed cortical expansion and perforation less frequently than the other cyst groups. Conclusion: Large cysts of mandible should be evaluated by multiplanar CT images inorder to detect the mandibular canal and cortical bone involvement.

• 한국공간구조학회논문집
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• 제12권4호
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• pp.99-108
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• 2012

In recently, sky-bridge are often applied to high-rised adjacent buildings for pedestrian bridge. the seisnic response control of adjacent buildings have been studied and magneto-rheological(MR) fluid dampers have been applied to seismic response control. In this study, vibration control effect of the MR damper connected adjacent buildings has been investigated. Adjacent building structures with different natural frequencies were used as example structures. Two typed of control methods, displacement based or velocity based, are applied to determinate control force of MR damper. In this numerical analysis, it has been shown that displacement-based control algorithm is more effective than velocity-based control algorithm for seismic response control of adjacent buildings. And, when displacement-based control method is applied to control of adjacent buildings, the control of building occurred large displacement is more efficient in reducing the seismic response.

• 한국지진공학회논문집
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• 제20권5호
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• pp.311-318
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• 2016

The lead-rubber bearing (LRB) dissipates seismic energy through plastic deformation of lead core. Under large-displacement cyclic motion, the temperature increases in the lead core. The shear strength of a lead-rubber bearing is reduced due to the heating effect of the lead core. In this study, the seismic responses such as displacement increasing, shear strength and vertical stiffness degradations of LRB due to the heating effect are evaluated for design basis earthquake (DBE) and beyond design basis earthquake (150% DBE, 167% DBE, 200% DBE).

• Macromolecular Research
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• 제14권6호
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• pp.624-629
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• 2006

The cellulose-based, Electroactive Paper (EAPap) has recently been reported as a smart material with the advantages of lightweight, dry condition, biodegradability, sustainability, large displacement output and low actuation voltage. However, it requires high humidity.. This paper introduces an EAPap made with a cellulose solution and lithium chloride (LiCl), which can be actuated in room humidity condition. The fabrication process, performance test and effect of LiCl content of the EAPap actuator are illustrated. The bending displacement of the EAPap actuators was evaluated with actuation voltage, frequency, humidity and LiCl content changes. At a LiCl/ cellulose content of 3:10, the displacement output was maximized at a room humidity condition. Even though the displacement output was less than that of a high humidity EAPap actuator, the mechanical power output was not reduced due to the increased resonance frequency, which is promising for developing EAPap actuators that are less sensitive to humidity.

• 한국산업융합학회 논문집
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• 제25권6_3호
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• pp.1231-1238
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• 2022

In this study, the reinforcement effect of the compression-only bridge seismic reinforcement method, which is mainly applied to old bridges, was studied through SSI analysis. As the analysis conditions, acceleration magnitudes of 0.1g, 0.15g, and 0.2 g were applied, and long-period and short-period seismic waves were applied. As a result of the analysis according to the assumed ground characteristics and structure size, the horizontal displacement at the reinforced section was reduced by about 9%, and the long-period seismic wave had a 95% larger displacement than the short-period seismic wave. In addition, an increase in acceleration of 0.1g resulted in a displacement of about 50%, and a large increase in displacement was observed in long-period seismic waves. As a result of the analysis, in the case of the compression-only bridge seismic reinforcement method, there was a reinforcing effect, so the field applicability was excellent.

• Geomechanics and Engineering
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• 제28권5호
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• pp.505-520
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• 2022

In recent years, geotextile-encased gravel columns (usually called stone columns) have become a popular method to increasing soil shear strength, decreasing the settlement, acceleration of the rate of consolidation, reducing the liquefaction potential and increasing the bearing capacity of foundations. The behavior of improved loose base-soil with gravel columns under shear loading and the shear stress-horizontal displacement curves got from large scale direct shear test are of great importance in understanding the performance of this method. In the present study, by performing 36 large-scale direct shear tests on sandy base-soil with different fine-content of zero to 30% in both not improved and improved with gravel columns, the effect of the presence of gravel columns in the loose soils were investigated. The results were used to predict the shear stress-horizontal displacement curve of these samples using support vector machines (SVM). Variables such as the non-plastic fine content of base-soil (FC), the area replacement ratio of the gravel column (Arr), the geotextile encasement and the normal stress on the sample were effective factors in the shear stress-horizontal displacement curve of the samples. The training and testing data of the model showed higher power of SVM compared to multilayer perceptron (MLP) neural network in predicting shear stress-horizontal displacement curve. After ensuring the accuracy of the model evaluation, by introducing different samples to the model, the effect of different variables on the maximum shear stress of the samples was investigated. The results showed that by adding a gravel column and increasing the Arr, the friction angle (ϕ) and cohesion (c) of the samples increase. This increase is less in base-soil with more FC, and in a proportion of the same Arr, with increasing FC, internal friction angle and cohesion decreases.

• Structural Engineering and Mechanics
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• 제62권5호
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• pp.619-629
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• 2017

This paper focuses on the study of complete dynamic modeling and maximum dynamic load carrying capacity computation of N-flexible links and N-flexible joints mobile manipulator undergoing large deformation. Nonlinear dynamic analysis relies on the Timoshenko theory of beams. In order to model the system completely and precisely, structural and joint flexibility, nonlinear strain-displacement relationship, payload, and non-holonomic constraints will be considered to. A finite element solution method based on mixed method is applied to model the shear deformation. This procedure is considerably more involved than displacement based element and shear deformation can be readily included without inducing the shear locking in the element. Another goal of this paper is to present a computational procedure for determination of the maximum dynamic load of geometrically nonlinear manipulators with structural and joint flexibility. An effective measure named as Moment-Height Stability (MHS) measure is applied to consider the dynamic stability of a wheeled mobile manipulator. Simulations are performed for mobile base manipulator with two flexible links and joints. The results represent that dynamic stability constraint is sensitive when calculating the maximum carrying load. Furthermore, by changing the trajectory of end effector, allowable load also changes. The effect of torsional spring parameter on the joint deformation is investigated in a parametric sensitivity study. The findings show that, by the increase of torsional stiffness, the behavior of system approaches to a system with rigid joints and allowable load of robot is also enhanced. A comparison is also made between the results obtained from small and large deformation models. Fluctuation range in obtained figures for angular displacement of links and end effector path is bigger for large deformation model. Experimental results are also provided to validate the theoretical model and these have good agreement with the simulated results.

• Coupled systems mechanics
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• 제5권1호
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• pp.41-58
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• 2016

The study deals with physical modeling of a typical building frame resting on pile raft foundation and embedded in cohesive soil mass using finite element based software ETABS. Both- the elements of superstructure and substructure (i.e., foundation) including soil is assumed to remain in elastic state at all the time. The raft is modelled as a thin plate and the pile and soils are treated as interactive springs. Both- the resistance of the piles as well as that of raft base - are incorporated into the model. Interactions between raft-soil-pile are computed. The proposed method makes it possible to solve the problems of uniformly and large non-uniformly arranged piled rafts in a time saving way using finite element based software ETABS. The effect of the various parameters of the pile raft foundation such as thickness of raft and pile diameter is evaluated on the response of superstructure. The response included the displacement at the top of the frame and bending moment in columns. The soil-structure interaction effect is found to increase displacement and increase the absolute maximum positive and negative moments. The effect of the soil- structure interaction is observed to be significant for the type of foundation and soil considered in the present study.