• Journal of the Korean Geotechnical Society
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• v.36 no.1
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• pp.5-15
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• 2020

Dynamic behavior of pile foundation is significantly influenced by the dynamic interaction between soil and pile. Especially, in the sloping ground, the soil-pile interaction becomes very complex due to different resistance according to loading direction, soil residual displacement and so on. In this study, dynamic centrifuge tests were performed on the piles in the sloping ground. The model structures consisted of a single pile and 2×2 group pile. The soil-pile interaction has been investigated considering various conditions such as slope, single and group piles, and amplitude of input motions. The phase differences between soil and pile displacement and dynamic p-y curves were evaluated. The analysis results showed that the pile behavior was largely influenced by the kinematic forces between soil and pile. In addition, the dynamic p-y curve showed the complex hysteresis loop due to the effect of slope, residual displacement, and kinematic forces.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.79-88
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• 2003

For the construction of PC bridge piers the implementation of 1992 seismic provisions, longitudinal steels were practically lap-spliced in the plastic hinge region. Experimental investigation was conducted ductility of evaluate the seismic earthquake-experienced reinforced concrete columns with 2,5 aspect ratio. Six test specimens were mode with test parameters: confinement ratios, lap splices, and retrofitting FRP materials. They were damaged under series of artificial earthquakes that could be compatible in Korean peninsula. Directly after the pseudo-dynamic test, damaged columns were retested under inelastic reversal cyclic loading simultaneously under a constant axial load, P＝0.1f$\_$ck/A$\_$g/. Residual seismic performance of damaged columns was evaluated and compared to that of the corresponding original columns. Test results show that PC bridge piers with lap-spliced longitudinal steels appeared to fail at low ductility. This was due to the debonding of the lap splice, which resulted from insufficient development of the longitudinal steels. The specimens externally wrapped with composite FRP straps in the potential plastic hinge region indicated significant improvement both in flexural strength and displacement ductility.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.42 no.4
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• pp.27-32
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• 2005

Liquid valve is divided into cylinder and liquid part or composed of a single body structure. It becomes a connected structure to cylinder head after inserting stainless(STS) shaft to Teflon packing. In injecting and intercepting fluid, working efficiency becomes low because of the top and bottom round trip operation the friction between Teflon packing and STS shaft fluid leakage, decline of working environment, and each part replacement. And so target value is unattainable in productivity liquid valve design, quality, and structure change are studied. In this paper, designed to solve the existing problems basically, to prevent friction of Piston by developing diaphragm linked with piston, to satisfy long life, and to provide the prevention of leakage. The objective of the study is also to prevent remains fluid at nozzle tip after dispensing fluid, and bell close with the suction function in piston retreating.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.3
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• pp.37-41
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• 2002

In this research, we investigate the properties of membrane and thin film sensor which is using magnetic resonance properties. we expect to $Si_xN_y$ and SiC materials as membrane materials, we measured thin film stress and properties to find the best membrane fabrication condition. Of the two membrane, $Si_xN_y$ thin film is the better than SiC thin film. because of an adequate tensile stress and lower thermal expansion coefficient as sensor structure layer. After performing deposition and patterning thin film sensor material on $Si_xN_y$, we analyzed the magnetic hysteresis and magnetic resonance frequency of sensor. If the magnetic field which is applied in sensor material is removed, magnetization made by magnetic field is transited to elastic mode. moreover. energy radiation is induced during the transition and voltage generates in sensor by energy radiation. At this moment, If voltage generation period is longer, mechanical vibration is induced and signal is generated by mechanical vibration. we also see that as the increase of thin film sensor' length and width, magnetic resonance frequency is decreased.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.6
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• pp.23-32
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• 2007

This study developed an analytical model for predicting nonlinear behavior of PT flat plate frames having slab-column connections with and without slab bottom reinforcement passing through the column. The developed model can predict the failure sequence until punching failure occurs. For verifying the analytical model, the test results of PT flat plate slab-column connections were compared with the results of the analysis. Moreover, the results of static pushover test and shaking table test of 2 story PT flat plate frame were compared with analysis results. For evaluating seismic performance of PT flat plate frame, this study conducted nonlinear response history analysis of the 2 story PT flat plate frame with and without slab bottom reinforcement passing through the column under 1940 El Centro ground motion scaled to have pseudo spectral acceleration of 0.3, 0.5, and 0.7g at the fundamental period of the frame. This study observed that as ground motion is more intense, seismic demands for the frame having the connections without slab bottom reinforcement passing through the column are larger than those without slab bottom reinforcement.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.6
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• pp.367-380
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• 2014

Tsunami take away life, wash houses away and bring devastation to social infrastructures such as breakwaters, bridges and ports. The targeted coastal structure object in this study can be damaged mainly by the tsunami force together with foundation ground failure due to scouring and liquefaction. The increase of excess pore water pressure composed of oscillatory and residual components may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, the solitary wave was generated using 2D-NIT(Two-Dimensional Numerical Irregular wave Tank) model, and the dynamic wave pressure acting on the seabed and the estimated surface boundary of the vertical revetment. Simulation results were used as an input data in a finite element computer program(FLIP) for elasto-plastic seabed response. The time and spatial variations in excess pore water pressure, effective stress, seabed deformation, structure displacement and liquefaction potential in the seabed were estimated. From the results of the analysis, the stability of the vertical revetment was evaluated.

• Journal of Korean Society of Steel Construction
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• v.22 no.6
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• pp.553-561
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• 2010

The purpose of this paper is to analytically find the approximate supplement damping ratio of the viscous damper installed in self-centering (SC) single-degree-of-freedom (SDOF) systems with maximum displacements that are similar to those of elasto-plastic (EP) SDOF systems. The behavior of an SC SDOF system under harmonic cyclic loading was first described. Then an analytical model that can capture the behavior of the viscously damped SC SDOF system was introduced. Analysis parameters that characterize the hysteresis of the EP and SC SDOF systems were chosen, and nonlinear time-history analyses were performed using 20 historical accelerograms. Most of the SC SDOF systems with viscous dampers with approximately 10-15% damping ratios presented mean maximum displacement values that were similar to those of the EP SDOF systems. To investigate in detail the seismic performance of both systems, three EP SDOF systems and six corresponding SC SDOF systems were selected. The analyses showed that all the SC SDOF systems eliminated the residual displacements after the end of their shaking, and that the SC SDOF systems with 15% damping ratios performed better than the EP SDOF systems in terms of maximum displacement and acceleration response.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.63-77
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• 2015

Tsunami take away life, wash houses away and bring devastation to social infrastructures such as breakwaters, bridges and ports. The coastal structure targeted object in this study can be damaged mainly by the wave pressure together with foundation ground failure due to scouring and liquefaction. The increase of excess pore water pressure composed of oscillatory and residual components may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, the bore was generated using the water level difference, its propagation and interaction with a vertical revetment analyzed by applying 2D-NIT(Two-Dimensional Numerical Irregular wave Tank) model, and the dynamic wave pressure acting on the seabed and the surface boundary of the vertical revetment estimated by this model. Simulation results were used as input data in a finite element computer program(FLIP) for elasto-plastic seabed response. The time and spatial variations in excess pore water pressure ratio, effective stress path, seabed deformation, structure displacement and liquefaction potential in the seabed were estimated. From the results of the analysis, the stability of the vertical revetment was evaluated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.457-463
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• 2012

The basilar membrane (BM), one of organs of cochlea, has the specific positions of the maximum amplitude at each of related frequencies. This phenomenon is due to the geometry of BM. In this study, as the part of the research for the development of fully implantable artificial cochlea which is based on polymer membrane, parametric studies are performed to suggest the desirable artificial basilar membrane model which can detect wider range of frequency separation. The vibro-acoustic characteristics of the artificial basilar membrane are predicted through finite element analysis using commercial software Abaqus. Simulation results are verified by comparing with experimental results. Various geometric shapes of the BM and residual stress effects on the BM are investigated through the parametric study to enable a wider detectable frequency separation range.

• Journal of the Korean Geotechnical Society
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• v.30 no.7
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• pp.27-40
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• 2014

So far, studies on the settlement of breakwater have mainly been conducted through numerical model tests focusing on an analysis or through the laboratory wave tank tests using a scaled model. There has not been a study on the settlement that is measured in an actual breakwater structure. This study analyzed the data of settlement that has been measured in an actual caisson breakwater for a long time and the characteristics and causes of wave-induced settlement in the caisson (including beneath ground), based on qualitative aspect, were examined. The analysis revealed that wave clearly has an effect on the settlement in caisson, especially in the condition of high wave such as typhoon. Caisson settlement is caused by the liquefaction of ground, which is due to the increase of excess pore pressure, the combination of oscillatory excess pore pressure and residual excess pore water pressure, and the solidification process of ground due to dissipation of the accumulated excess pore pressure. The behavior of excess pore pressure in the ground beneath the caisson is entirely governed by the behavior of the caisson. Ground that has gone through solidification is not likely to go through liquefaction in a similar or a smaller wave condition and consequently, the possibility of settlement is reduced.