• Proceeding of KASS Symposium
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• 2008.05a
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• pp.133-138
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• 2008

In this study, the seismic behavior of arch structure with lead rubber bearing(LRB) is analyzed. The arch structure is the simplest structure and has the basic dynamic characteristics among large spatial structures. Also, Large spatial structures have large vertical response by horizontal seismic vibration, unlike seismic behavior of normal rahmen structures. When horizontal seismic load is applied to the large spatial structure with isolation systems, the horizontal acceleration response of the large spatial structure is reduced and the vertical seismic response is remarkably reduced.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.1
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• pp.43-49
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• 2007

Multi-function and miniaturization of the medical equipment and tele-communication systems need small and high precision machined parts. For the economic machining of the small size workpiece it should be machined by small and high precision machine tools with high speed machining. The belt type driving system in turning lathe has a limitation of spindle speeds because of the vibrations from driving mechanism, built-in type of driving mechanism is used to reduce the vibration. However, the main spindle of the built-in motor is connected directly to the motor, so the heat generation of the motor and bearing makes bad influence of the accuracy of machine tools. In this study, the analysis of heat generation from motor and bearings supporting main spindle and experiment were carried out. The results of theoretical simulation of temperature and deformation of the main spindle are good agreement with those of measured.

• Earthquakes and Structures
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• v.19 no.4
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• pp.261-272
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• 2020

Recent severe earthquakes in and around the vital public places worldwide indicate the severe vulnerability of ground excitation to be assailed. Reducing the effect of seismic lateral load in structural design is an important conception. Essentially, seismic isolation is required to shield the superstructure in such a way that the building superstructure would not move when the ground is shaking. This study explores the effectiveness, design, and practical feasibility of base isolation systems to reduce seismic demands on buildings of varying elevations. Thus, static and dynamic analyses were conducted based on site-specific bi-directional earthquakes for base-isolated as well as fixed-based buildings. Remarkably, it was discovered that isolators used in low-rise to high-rise structures tend to significantly decrease the structural responses of seismic prone buildings. The higher allowable horizontal displacement induces structural flexibility and ensure good structural health of the building stories. Reinforcement from vertical and horizontal members can be reduced in significant amounts for BI buildings. Thus, although incorporating base isolators increases the initial outlay, it considerably diminishes the total structural cost.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.3
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• pp.285-294
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• 2012

Using bearing measurement only, target motion state is not directly obtained so that TMA (Target Motion Analysis) is needed for this situation. TMA is a nonlinear estimation technique used in passive SONAR systems. Also it is the one of important techniques for underwater combat management systems. TMA can be divided to two parts: batch estimation and sequential estimation. It is preferable to use sequential estimation for reducing computational load as well as adaptively to target maneuvers, batch estimation is still required to attain target initial state vector for convergence of sequential estimation. Selection of batch time interval which depends on observability is critical in TMA performance. Batch estimation in general utilizes predetermined batch time interval. In this paper, we propose a new method called the BTIS (Batch Time Interval and Initial State Estimation). The proposed BTIS estimates target initial status and determines the batch time interval sequentially by using a bank of GMM-TS (Gaussian Mixture Measurement-Track Splitting) filters. The performance of the proposal method is verified by a Monte Carlo simulation study.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.461-472
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• 2010

This paper investigates the behavior of precast concrete (PC) shear walls with a new vertical connections for a fast remodeling construction. The C-type vertical connections for the PC wall systems are proposed for transfer of bending moment between top and bottom walls in the vertical direction while a shear key in the center of wall is prepared to transfer shear forces by bearing action. The proposed vertical connections allows easy fabrication thanks to slots at the edges of wall in opposite directions. The plane PC wall systems subject to lateral load are compared with ordinary wall systems by investigating the effects of connection on the stiffness, strength, ductility, and failure modes of whole systems. The load-displacement relationship and influence of premature failure of connections are examined. The experimental test showed that the longitudinal reinforcing steel bars placed at the edges of walls yielded first and the ultimate deformation were terminated due to premature failure of connections. The diagonal reinforcements for efficient shear transfer in the walls were not effective. The strength and deformation obtained through the section analysis were generally in agreement with the experimental data, and indicated that. Gap opening contributed to the deformation behavior more than any other factors.

• Transactions of the Society of Information Storage Systems
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• v.2 no.2
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• pp.130-137
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• 2006

The HDD(hard disk drive) using Load/unload(L/UL) technology includes the benefits which are increased areal density, reduced power consumption and improved shock resistance than those of contact-start-stop(CSS). It has been widely used in portable hard disk drive and will become the key technology for developing the small form factor hard disk drive. The main objects of L/UL are no slider-disk contact or no media damage. For realizing those, we must consider many design parameters in L/UL system. In this paper, we focus on lift-off force. The 'lift-off' force, defined as the minimum air bearing force, is another very important indicator of unloading performance. A large amplitude of lift-off force increases the ramp force, the unloading time, the slider oscillation and contact-possibility. To minimize 'lift-off' force we optimizes the slider and suspension using the integrated optimization frame, which automatically integrates the analysis with the optimization and effectively implements the repetitive works between them. In particular, this study is carried out the optimal design considering the process of modes tracking through the entire optimization processes. As a result, we yield the equation which can easily find a lift-off force and structural optimization for suspension.

• Steel and Composite Structures
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• v.26 no.3
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• pp.361-373
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• 2018

This paper presents the development of finite element (FE) models to simulate the behavior of diagonally stiffened steel plate shear wall systems (SPSWs) with differently shaped openings subjected to a cyclic load. This walling system has the potential to be used for shear elements that resist lateral loads in steel-framed buildings. A number of $\text\tiny{^1/_2}$-scale one-story buildings that were un-stiffened, stiffened and stiffened with opening SPSWs are modeled and simulated using the finite element method based on experimental data from previous research. After validating the finite element (FE) models, the effects of infill plate thickness on the cyclic behavior of steel shear walls are investigated. Furthermore, triple diagonal stiffeners are added to the steel infill plates of the SPSWs, and the effects are studied. Moreover, the effects of a number of differently shaped openings applied to the infill plate are studied. The results indicate that the bearing capacity and shear resistance are affected positively by increasing the infill plate thickness and by adding triple diagonal stiffeners. In addition, the cyclic behavior of SPSWs is improved, even with an opening in the SPSWs.

• Tribology and Lubricants
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• v.30 no.3
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• pp.131-138
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• 2014

This study investigates the effects of the slopes of the rotational axis and bearing preloads on the natural frequencies and onset speeds of the instability of a rotor supported on gas foil bearings (GFBs). The predictive model for the rotating system consists of a rigid rotor supported on two gas foil journal bearings (GFJBs) and a pair of gas foil thrust bearings (GFTBs). Each GFJB supports approximately half the rotor weight. As the slope of the rotational axis increases from $0^{\circ}$(horizontal rotor operation) to $90^{\circ}$(vertical rotor operation), the applied load on the GFJB owing to the rotor weight decreases. The predictions show that the natural frequency and onset speed of instability decrease significantly with an increase in the slope of the rotational axis. In a parametric study, the nominal radial clearance and preload for the GFJB were changed. In general, a decrease in the nominal radial clearance lead to an increase in the natural frequency and onset speed of instability. For constant assembly clearance, the decrease in the preload changed the natural frequency and onset speed of instability with insignificant improvements in the rotordynamic stability. The present predictions can be used as design guidelines for GFBs for oil-free high-speed rotating machinery with improved rotordynamic performance.

• Structural Engineering and Mechanics
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• v.87 no.2
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• pp.137-149
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• 2023

In this study, to explore the working performance of the CFST split spherical node wind power tower, two groups of CFST split spherical joint plane towers with different web wall thicknesses and a set of space systems were analyzed. The tower was subjected to a low-cycle repeated load test, and the hysteresis and skeleton curves were analyzed. ABAQUS finite element simulation was used for verification and comparison, and on this basis parameter expansion analysis was carried out. The results show that the failure mode of the wind power tower was divided into weld tear damage between belly bar, high strength bolt thread damage and belly rod flexion damage. In addition, increasing the wall thickness of the web member could render the hysteresis curve fuller. Finally, the bearing capacity of the separated spherical node wind power tower was high, but its plastic deformation ability was poor. The ultimate bearing capacity and ductility coefficient of the simulated specimens are positively correlated with web diameter ratio and web column stiffness ratio. When the diameter ratio of the web member was greater than 0.13, or the stiffness ratio γ of the web member to the column was greater than 0.022, the increase of the ultimate bearing capacity and ductility coefficient decreased significantly. In order to maximize the overall mechanical performance of the tower and improve its economy, it was suggested that the diameter ratio of the ventral rod be 0.11-0.13, while the stiffness ratio γ should be 0.02-0.022.

• Journal of the Korean Wood Science and Technology
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• v.33 no.2 s.130
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• pp.8-16
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• 2005

In an effort to encourage the development of value added engineered applications for small diameter round timber, research is being conducted to develop and verify design guidelines for connections with specific application to round timbers. The objective of this research is to provide potential users with a number of viable connection options applicable in the fabrication of engineered, round wood structural components and systems. Target uses include trusses, built up flange beams and space frames. This paper presents information on a mortised steel plate connection fabricated using powder driven nails in 6 cm diameter Japanese Larch. The design load for PDN connections are around 1.3 kN per nail with strip and 0.8 kN per nail without stripe. The design model for PDN connectors could be chosen by the number of nails. If the number of nails are more than the critical number between nail bearing and wood failure, the wood failure model could be the way to design the structure safely. The wood failure model needs to be studied more but the model could be the tensile and cleavage mixed failure model.