• 한국지진공학회논문집
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• 제21권5호
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• pp.227-236
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• 2017

This study reviews concepts, theories and formulas included in standards on soil-structure interaction and also shows practical example of application for engineers. Real structures are 3 dimensional and multi degree of freedom but they are often idealized to single degree of freedom for convenience. In this study, detailed procedures to calculate soil spring constants and damping coefficients and method to model soil-structure system are explained. Additionally, case studies to judge fixed base condition and evaluation of applicability of simple analysis method based on response spectra are performed.

• 대한치과보철학회지
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• 제28권1호
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• pp.63-94
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• 1990

The purpose of this study was to analyze the displacement and the magnitude and the mode of distribution of the stresses in the lower overdenture, the mucous membrane, the abutment tooth and the mandibular supporting bone when various denture base materials, such as acrylic resin and 0.5mm metal base, and various denture base designs were subjected to different loading schemes. For this study, the two-dimensional finite element method was used. Mandibular arch models, with only canine remaining, were fabricated. In the first denture base design, a space, approximately 1mm thick, was prepared between the denture and the dome abutment. In the second denture base design, contact between the denture and the dome abutment was eliminated except the contact of the occlusal third of the abutment. In order to represent the same physiological condition as the fixed areas of the mandible under loading schemes, the eight nodes which lie at the mandibular angle region, the coronoid process and the mandibular condyle were assumed to be fixed. Each model was loaded with a magnitude of 10 kgs on the first molar region(P1) and 7 kgs on the central incisal region (P2) in a vertical direction. Then the force of 10 kgs was applied distributively from the first premolar to the second molar of each model in a vertical direction(P3). The results were as follows. : 1. When the testing vertical loads were given to the selected points of the overdenture, the overdenture showed the rotatory phenomenon, as well as sinking and the displacements of alveolar ridge, abutment and lower border of mandible under the metal base overdenture were less than those under the acrylic resin overdenture. 2. The maximum principal stresses(the maximum tensile stresses) being considered, high tensile stresses occured at the buccal shelf area, the posterior region of the ridge crest and the anterior border region of the mandibular ramus. 3. The minimum principal stresses(the maximum compressive stresses) being considered, high compressive stresses occured at the inferior and posterior border region of the mandible, the mandibular angle and the posterior border region of the mandibular ramus. 4. The vertical load on the central incisal region(P2) produced higher equivalent stress in the mandible than that on any other region(P1, P3) because of the long lever arm distance from the fixed points to the loading point. 5. Higher equivalent stresses were distributed throughout the metal base overdenture than the resin base overdenture under the same loading condition. 6. The case of occlusal third contact of the abutment to the denture produced higher equivalent stresses in the abutment, the mandibular area around the abutment and the overdenture than the case of a 1mm space between the denture and the abutment. 7. Without regard to overdenture base materials and designs, the amounts and distribution patterns of equivalent stresses under the same loading condition were similar in the mucous membrane.

• Journal of Mechanical Science and Technology
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• 제20권8호
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• pp.1224-1231
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• 2006

The stability and control derivatives of DURUMI-lI UAV using the flight test are obtained. The flight test data is gathered from the normal flight condition (normal mode) and the flight condition assumed as the right elevator fixed (fault mode). Using real-time parameter estimation techniques, applied to Fourier transform regression method, simulates the aircraft motion. From the result, the fault of control surface is to be detected. In this paper, the results of the real- time parameter estimation techniques are compared with the results of the Advanced Aircraft Analysis (AAA). Using the aerodynamic derivatives, it provides the base line of normal/failure for the control surface by using the on-line parameter estimation of Fourier transform regression. In flight, this approach maybe helpful to detect and isolate the fault of primary control surface. It is explained how to perform the flight condition assumed as the right elevator fixed in the flight test. Also, it is mentioned how to switch between the normal flight condition and the assumed fault flight condition.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.528-533
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• 2002

The mechanical and metallurgical properties of friction welded joints type 5052 Al alloy/A36 steel have been studied in this paper. The joint strength increased with increasing upset pressure and friction time till it reached the critical value. The joint strength was fixed at low strength compare to that of base metal in the case of increasing friction time. Microstructure of 5052 Al alloy was greatly deformed near the weld interface. The very fine and equaxied grain structure was observed at the near interface. The elongated grain was formed outside dynamic recrystallizatoin region at the peripheral part, while the A36 steel' side was not deformed. The hardness of the near interface was slightly softer than that of 5052 Al alloy base metal. The maximum softening width was about 8mm from the interface. In the present work, the friction welding condition, t$_1$=0.5sec, P$_2$=137.5MPa, showed a maximum joint strength (202MPa) when friction pressure, upset time and rotation speed were fixed at 75MPa, 5sec, 2000rev/min and these were the optimum friction welding condition of 5052Al/A36 steel joints.

• 정보저장시스템학회논문집
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• 제9권2호
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• pp.32-35
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• 2013

Nowadays, function related to anti-vibration and anti-shock of storage devices is required because of portability. Therefore, many hard disk drive (HDD) studies about external shock and vibration have been performed. Especially, many studies are performed with non-operational shock. Most studies have used the fixed condition between spindle system and base when they wanted to analyze dynamic behavior of inner parts in simulation. But spindle system has actually stiffness and damping coefficient. Maybe difference of value would be happened between fixed condition and spring condition. So, we measured FRF of spindle system to know stiffness and damping coefficient in HDD. And we studied on dynamic behavior of inner parts by using calculated stiffness and damping coefficient. As a result, we confirmed the difference as boundary condition of spindle system.

• 한국실내디자인학회논문집
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• 제17권5호
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• pp.40-50
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• 2008

This article examined the applicability of spatial configuration to Escher's works through configurative logics and rules and studied the contrasting relations among the unit elements in Escher's works and their characteristics and the creative process of the characteristics. As the results of the study on the bases to maintain and create the partial elements revealed as the characteristics, it was shown that Escher's sequential transformative works demonstrated diverse expressive characteristics as a creative process of Inter-complementary contrasting relations based on the independence of the unit elements. It was also shown that the creative process of the unit elements was actualized through the maintenance base of the fixed and absolute characteristic as the logic for the creation and the creation base of the dynamic and relative characteristic. Therefore, it was interpreted that by applying the logics for creation to Escher's unit elements through the spatial interpretation of the maintenance base and the creation base as well as by configuring the units created in such a way according to the characteristics of Escher's works, spatial possibility canbe derived out from Escher's contrasting tessellation works. The process of spatial configuration is the process to make a balance between various conditions, artists own understanding of the space and his/her intention of the space. From this viewpoint, the logics for maintenance base and for creation base seem to have the potentiality as a spatial configuration to consistently meet the given conditions as well as to derive out novelty through the transformation to maintain the fixed and absolute condition(base) and the characteristics of the independent(additional) transformation arising together with the implicit relations among the transformative units.

• Structural Engineering and Mechanics
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• 제51권2호
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• pp.277-297
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• 2014

Since the isolation bearings undergo large displacements in base-isolated structures, impact with adjacent structures is inevitable. Therefore, in this investigation, the effect of impact on seismic response of isolated structures mounted on double concave friction pendulum (DCFP) bearings subjected to near field ground motions is considered. A non-linear viscoelastic model of collision is used to simulate structural pounding more accurately. 2-, 4- and 8-story base-isolated buildings adjacent to fixed-base structures are modeled and the coupled differential equations of motion related to these isolated systems are solved in the MATLAB environment using the SIMULINK toolbox. The variation of seismic responses such as base shear, displacement in the isolation system and superstructure (top floor) is computed to study the impact condition. Also, the effects of variation of system parameters: isolation period, superstructure period, size of seismic gap between two structures, radius of curvature of the sliding surface and friction coefficient of isolator are contemplated in this study. It is concluded that the normalized base shear, bearing and top floor displacement increase due to impact with adjacent structure. When the distance between two structures decreases, the base shear and displacement increase comparing to no impact condition. Besides, the increase in friction coefficient difference also causes the normalized base shear and displacement in isolation system and superstructure increase in comparison with bi-linear hysteretic behavior of base isolation system. Totally, the comparison of results indicates that the changes in values of friction coefficient have more significant effects on 2-story building than 4- and 8-story buildings.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권1호
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• pp.9-20
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• 2018

Due to integrated stochastic wind and wave loads, the supporting platform of a Floating Offshore Wind Turbine (FOWT) has to bear six Degrees of Freedom (DOF) motion, which makes the random cyclic loads acting on the structural components, for instance the tower base, more complicated than those on bottom-fixed or land-based wind turbines. These cyclic loads may cause unexpected fatigue damages on a FOWT. This paper presents a study on short-term fatigue damage at the tower base of a 5 MW FOWT with a spar-type platform. Fully coupled time-domain simulations code FAST is used and realistic environment conditions are considered to obtain the loads and structural stresses at the tower base. Then the cumulative fatigue damage is calculated based on rainflow counting method and Miner's rule. Moreover, the effects of the simulation length, the wind-wave misalignment, the wind-only condition and the wave-only condition on the fatigue damage are investigated. It is found that the wind and wave induced loads affect the tower base's axial stress separately and in a decoupled way, and the wave-induced fatigue damage is greater than that induced by the wind loads. Under the environment conditions with rated wind speed, the tower base experiences the highest fatigue damage when the joint probability of the wind and wave is included in the calculation. Moreover, it is also found that 1 h simulation length is sufficient to give an appropriate fatigue damage estimated life for FOWT.

• 한국지진공학회논문집
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• 제19권4호
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• pp.161-171
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• 2015

A series of tests was conducted for full-scale single-pylon asymmetric cable-stayed bridges using a system of multiple shaking tables. The 2-span bridge length was 28 m, and the pylon height was 10.2 m. 4 different base conditions were considered: the fixed condition, RB (rubber bearings), LRB (lead rubber bearings), and HDRB (high damping rubber bearings). Based on investigation of the seismic response, the accelerations and displacements in the axial direction of the isolated bridge were increased compared to non-isolated case. However, the strain of the pylon was decreased, because the major mode of the structure was changed to translation for the axial direction due to the dynamic mass. The response of the cable bridge could differ from the desired response according to the locations and characteristics of the seismic isolator. Therefore, caution is required in the design and prediction in regard to the location and behavior of the seismic isolator.

• 한국지진공학회논문집
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• 제26권3호
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• pp.117-125
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• 2022

In this study, centrifuge model tests were performed to evaluate the seismic response of multi-DOF structures with shallow foundations. Also, elastic time history analysis on the fixed-base model was performed and compared with the experimental results. As a result of the centrifuge model test, earthquake amplification at the fundamental vibration frequency of the soil (= 2.44 Hz) affected the third vibration mode frequency (= 2.50 Hz) of the long-period structure and the first vibration mode (= 2.27 Hz) of the short-period structure. The shallow foundation lengthened the periods of the structures by 14-20% compared to the fixed base condition. The response spectrum of acceleration measured at the shallow foundation was smaller than that of free-field motion due to the foundation damping effect. The ultimate moment capacity of the soil-foundation system limited the dynamic responses of the multi-DOF structures. Therefore, the considerations on period lengthening, foundation damping, and ultimate moment capacity of the soil-foundation system might improve the seismic design of the multi-DOF building structures.