• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.5
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• pp.85-94
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• 1996

For the geotechnical analysis in the construction and Deign of the coastal structures, one of the most important factors is the existence of waves. The dynamic behavior and deformation of the seabed subjected to wave load must be considered. It is expected that the soil behavior in the seabed subjected to cyclic wave load is much different from that on the ground subjected to dynamic forces such as earthquake. The purposes of this study are as follows ; Firstly, to provide a testing method to generate wave loads in the laboratory and measuring oscillatory pore water pressures in the unsaturated marine silty sand specimen, Secondly, to analyze the mechanism of wave induced pore water pressures and liquefaction potentials under the conditions in the testing. It is shown that the test set-up manufactured especially for the test is good to generate oscillatory wave pressures to the specimen with sine wave type. From the results of this study, it is understood that the pore water pressure due to induced waves is not accumulated as the wave number increases but is periodically varied with wave passage on still water surface. The magnitude of pore water pressures measured tends to be diminished radically with a certain time lag under the action of both high and low waves as depth increases.

• Structural Engineering and Mechanics
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• v.31 no.6
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• pp.639-662
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• 2009

A comprehensive investigation of the stochastic response of an isolated cable-stayed bridge subjected to spatially varying earthquake ground motion is performed. In this study, the Jindo Bridge built in South Korea is chosen as a numerical example. The bridge deck is assumed to be continuous from one end to the other end. The vertical movement of the stiffening girder is restrained and freedom of rotational movement on the transverse axis is provided for all piers and abutments. The longitudinal restraint is provided at the mainland pier. The A-frame towers are fixed at the base. To implement the base isolation procedure, the double concave friction pendulum bearings are placed at each of the four support points of the deck. Thus, the deck of the cable-stayed bridge is isolated from the towers using the double concave friction pendulum bearings which are sliding devices that utilize two spherical concave surfaces. The spatially varying earthquake ground motion is characterized by the incoherence and wave-passage effects. Mean of maximum response values obtained from the spatially varying earthquake ground motion case are compared for the isolated and non-isolated bridge models. It is pointed out that the base isolation of the considered cable-stayed bridge model subjected to the spatially varying earthquake ground motion significantly underestimates the deck and the tower responses.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.50-59
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• 1997

When a front head of train enters a tunnel at a high speed, compression wave is generated at tunnel entrance due to the confinement effect and propagated along the tunnel with sound of speed. The propagated compression wave is reflected at tunnel exit due to abrupt pressure change at passage. The reflected wave is expansion pressure wave. And when the rear head of train goes through the tunnel entrance, another expansion pressure wave is generated and propagated along the tunnel. The pressure drop occurs seriously around train when the two expansion pressure waves come cross on train in the tunnel. In order to reduce the pressure drop, the compression wave front must be controlled because the intensity and magnitude of pressure drop is nearly proportional to that of compression wave at tunnel entrance. This study relates to reduction of the pressure wave gradient with respect to tunnel entrance shape change with various kind of angle and rounding. The results show characteristics of wave propagation in tunnel, usefulness of characteristic curve to estimate proper time domain size in numerical study and measuring time in actual experiment. Also rounding is contributed to improve pressure wave front even if its radius is very small at tunnel entrance. In order to improve of pressure wave front at tunnel entrance, proper angle is prefered to rounding with big radius and an angle of around 14$^{\circ}$ is recommended according to this simulations, And it is expected to reduce additional pressure drop in tunnel when the location and the size of the internal space for attendant equipment are considered in advance.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.2
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• pp.41-48
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• 2003

The human behavior is very important in development of simulation system for evacuation analysis. The walking speed of passenger is especially affected by dynamic effect and list due to damage and ship motion in wave. There are various methods to get an useful data for evacuation simulation. The onboard experimental approach is one of the most strong method. In this paper, the onboard experiment is performed to obtain human behavioral data. To realize ship trim and heel due to maritime casuality, the passage model for experiment is made. The experiment is carried out at dynamic and static condition respectively using the ship with passage model. The result is evaluated and it will be reflected in evacuation simulation tool.

• Journal of Mechanical Science and Technology
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• v.15 no.3
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• pp.366-373
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• 2001

A numerical analysis of shock wave/boundary layer interaction in transonic/supersonic axial flow compressor cascade has been performed by using a characteristics upwind Navier-Stokes method with various turbulence models. Two equation turbulence models were applied to transonic/supersonic flows over a NACA 0012 airfoil. The results are superion to those from an algebraic turbulence model. High order TVD schemes predicted shock wave/boundary layer interactions reasonably well. However, the prediction of SWBLI depends more on turbulence models than high order schemes. In a supersonic axial flow cascade at M=1.59 and exit/inlet static pressure ratio of 2.21, k-$\omega$ and Shear Stress Transport (SST) models were numerically stables. However, the k-$\omega$ model predicted thicker shock waves in the flow passage. Losses due to shock/shock and shock/boundary layer interactions in transonic/supersonic compressor flowfields can be higher losses than viscous losses due to flow separation and viscous dissipation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.646-655
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• 2002

장대 교량이 위치한 지반에서 지진에 의한 지반 운동은 교량의 길이 방향으로 공간적인 변화를 일으킨다. 지형 변화나 지반 매질의 물성 변화가 있는 비균질한 지반에서 지반 운동의 진폭과 주파수 성분은 변화하고 이 부지 효과(site effect)는 교량의 지진 응답에 지배적인 영향을 미치며 그 영향은 파전파 효과(wave passage effect)에 의한 지반 각 지점의 지진파 도달시간 차이나 비균질성이 큰 지반에서 파의 다중 반사, 굴절에 의한 영향보다 크다[1]. (중략)

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.3
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• pp.170-176
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• 2012

This paper analyzes the sea state and characteristics during the August 2011 passage of Typhoon Muifa based on data measured at four ocean weather/wave observation stations (buoys) located on the southwestern coast of Korea. When the typhoon arrived in the area approximately 230 km west of Mokpo at 9 PM on August 7, the decrease in air pressure led to increases in sea level of 25.64 cm at the Chilbal-do buoy, 16.43 cm at the Geomun-do buoy, and 9.60 cm at the Geoje-do buoy. The maximum wave height increased at the Geomun-do buoy about seven times faster than at the Chilbal-do buoy. The low water temperature at Chilbaldo during the typhoon passage probably reduced the wave energy. In the face of the oncoming typhoon, the southwest direction of the wind and waves may have been the result of external forces transporting seawater (energy) from the open sea toward the coast. The weather and ocean data from the Mara-do buoy were negatively correlated with those of Chilbal-do, whereas the data from Geomun-do had a positive correlation with those of Geoje-do.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.50.3-50.3
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• 2019

The EUV wave is a disturbance that has been believed to be the fast-mode (shock) wave, which can propagate passing through magnetic field lines. After the passage of EUV waves, coronal streamers start to show kink-mode oscillations, and the footpoints, i.e., magnetic separatrices, of the oscillating streamers are observed as the so-called stationary front. We compare the stationary front observed by EUV imagers and coronal streamers observed in coronagraphic images. We analyze the successive events occurred in September 2011. We find that the stationary fronts are consistent with the coronal streamer boundaries, and they are located along the boundaries of coronal holes and active regions. Our results confirm that EUV waves are in fact fast-mode waves and demonstrate that the stationary front is a promising tool to probe into the source of slow solar wind that is the boundary of coronal streamers on the solar surface.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.47-58
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• 2005

Dynamic response analysis in time dimain is conducted for floating bridges with discrete pontoons subject to spatial variation of ground motions. The Spatial variation of ground motions is considered with the coherency function model which represents wave passage, incoherence and local site effects. The superstructure of the bridge is represented by space frame and elastic catenary cable elements, the abutment us modelde with the spring element of FHWA guideline for considering soil structure interaction and the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients which are obtainde by boundary element method. multiple support excitations considering the spatial variation. The noticeable amplification of the response can be shown when the spatial variation of ground motions is incorporated in the anallysis of floating bridges.

• Earthquakes and Structures
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• v.26 no.5
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• pp.401-416
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• 2024

Long-span structures, such as bridges, can experience different seismic excitations at the supports due to spatially variability of ground motion. Regarding current bridge designing codes, it is just EC 2008 that suggested some regulations to consider it and in the other codes almost ignored while based on some previous studies it is found that the effect of mentioned issue could not be neglected. The current study aimed to perform a comprehensive study about the effect of spatially varying ground motions on the dynamic response of a reinforced concrete bridge under asynchronous input motions considering soil-structure interactions. The correlated ground motions were generated by an introduced method that contains all spatially varying components, and imposed on the supports of the finite element model under different load scenarios. Then the obtained results from uniform and non-uniform excitations were compared to each other. In addition, the effect of soil-structure interactions involved and the corresponding results compared to the previous results. Also, to better understand the seismic response of the bridge, the responses caused by pseudo-static components decompose from the total response. Finally, an incremental dynamic analysis was performed to survey the non-linear behavior of the bridge under assumed load scenarios. The outcomes revealed that the local site condition plays an important role and strongly amplifies the responses. Furthermore, it was found that a combination of wave-passage and strong incoherency severely affected the responses of the structure. Moreover, it has been found that the pseudo-static component's contribution increase with increasing incoherent parameters. In addition, regarding the soil condition was considered for the studied bridge, it was found that a combination of spatially varying ground motions and soil-structure interactions effects could make a very destructive scenarios like, pounding and unseating.