• Earthquakes and Structures
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• 제9권3호
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• pp.625-637
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• 2015

It is usual in design and assessment of structures to isolate the effects of vertical and horizontal excitations by ignoring their coupling effects. In this situation, total structural response is obtained by employing the well-known combination rules whereby independent assumed response components of earthquakes are combined. In fact, the effects of the simultaneity of the ground motion components are ignored. In this paper, the effect of vertical excitation on horizontal response of structures, the coupling of vertical and horizontal responses, has been evaluated. A computer program is prepared to perform nonlinear dynamic analysis based on the derived governing equations of coupled motions. In the case of simultaneous excitation the results show significant increases in spectral displacement in some periods of vibration in comparison to only horizontally excited systems. Moreover, whenever ratio of the vertical peak ground acceleration to horizontal one become larger, the significant increase in horizontal spectral displacements are observed.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.81-88
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• 1998

During an earthquake, there are three main components of excitation : horizontal excitation of the ground, vertical excitation of the pile due to superstructure feedback produced by vertical excitation of the ground, and the seawater excitation induced by the vertical ground shaking, that is, "the seaquake." These excitations could have effects on the soil plugs in open-ended pipe piles installed at offshore sites. In this study, seaquake excitation induced by the vertical ground shaking was simulated by pulsing the water pressure at the seabed. During a seaquake, due to induced excess porewater pressure and pressure gradients in the soil, the capacity of open-ended pipe piles installed in a simulated sea depth of greater than 220 m was reduced serevely and the soil plugging resistance was degraded by more than 80%. The soil plug was failed because of the upward seepage forces that developed in the soil plug due to excess pore water pressure produced in the bottom of the soil plug during the seaquake. The compressive capacity of an open-ended pile in a simulated sea depth of less than 220m was reduced only by about 10%, and the soil plug resistance was degraded by less than 5%.s than 5%.

• Bulletin of the Korean Chemical Society
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• 제34권8호
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• pp.2276-2280
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• 2013

The accurate prediction of vertical excitation energies is very important for the development of new materials in the dye and pigment industry. A time-dependent density functional theory (TD-DFT) approach coupled with 22 different exchange-correlation functionals was used for the prediction of vertical excitation energies in the halogenated copper phthalocyanine molecules in order to find the most appropriate functional and to determine the accuracy of the prediction of the absorption wavelength and observed spectral shifts. Among the tested functional, B3LYP functional provides much more accurate vertical excitation energies and UV-vis spectra. Our results clearly provide a benchmark calibration of the TD-DFT method for phthalocyanine based dyes and pigments used in industry.

• 한국지진공학회논문집
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• 제2권1호
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• pp.11-21
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• 1998

해상에 설치된 기초말뚝의 경우 지진의 3가지 성분 즉, 지반의 수평운도, 지반의 연직진동에 의해 발생된 상부구조물과의 피드백 (feedback)에 의한 말뚝의 연직진동, 그리고 지반의 연직진동에 의해 유발된 해진(seaquake)의 진동이 말뚝 기초의 거동에 영향을 미친다. 본 연구에서는 유발된 해진의 진동을 해저면에서 유사화된 sine 정현파 형상의 동수압으로 모델링하였다. 해진(seaquake) 작용중 약 220m 이상의 심해에 설치된 개단 말뚝의 지지력은, 지반내에 유발된 과도한 과잉 간극수압으로 인하여, 심각하게 저감도었으며, 관내토 폐쇄력도 80% 이상 감소되었다. 해진중 관내토 선단 하부에서 발생된 과도한 과잉 간극수압으로 인하여 관내토내에 과도한 상향의 침투력이 유발되어 관내토 폐색이 손상되었다. 약 220m 이하의 천해에 설치된 개단말뚝의 지지력은 해진에 의해 약 10% 감소하였으며, 관내토의 폐쇄력은 5%이하만큼 감소하였다.

• 센서학회지
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• 제29권3호
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• pp.205-210
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• 2020

The aim of this study is to develop a vertical vibration compensator that attenuates the vertical vibration of ships. The vibration compensator was designed according to the principle of generating vertical excitation forces by rotating two eccentric bodies of the same mass in opposite directions at the same rotational speed. In addition, the structural stability was analyzed using the finite element method. The maximum stress in the drive shaft was 95.6 MPa, which was approximately 35% of the allowable stress of the shaft material (SM45C, 270 MPa). The acceleration signals of the vibrator compensator body and the testbed were determined to evaluate the efficiency of the vibration compensator and the designed excitation forces. Subsequently, the excitation forces were estimated based on the relationship between force and acceleration. The estimated results were very close to the theoretical values with an error of less than 3%.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.688-698
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• 2019

If heave motion in the platform causes horizontal parametric vibration of a Compliant Vertical Access Riser (CVAR), the riser may become unstable. A combination of riser parameters lies in the unstable region aggravates vibrational damage to the riser. Change of axial tensile stress in the riser combined with its natural frequency and mode shape change results in mode coupling. In accordance with the state transition matrices of the riser in the coupled and uncoupled states, the stable and unstable regions were obtained by Floquet theory, and the vibration response under different conditions was obtained. The parametric excitation of the CVAR is shown to occur mainly in first-order unstable regions. Mode coupling may cause parametric excitation in the least stable regions. Damping reduces the extent of unstable regions to a certain extent.

• 한국기계가공학회지
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• 제19권11호
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• pp.70-77
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• 2020

Vibratory bowl feeders are widely utilized to align and feed the parts stacked inside the bowl of a feeder. The electro-magnetic force of the electromagnet in a bowl feeder generates the excitation force for the bowl to vibrate in both the horizontal and vertical directions to continuously feed the parts on the track. The feed rate of the part depends on the associated displacement in each direction during the vibration. Therefore, the excitation force induced by the electromagnet should be estimated in advance to ensure the suitable design of the bowl feeder. In this study, a theoretical solution was developed to calculate the electro-magnetic force of the electromagnet for a bowl feeder. Using the proposed solution, the electro-magnetic forces corresponding to a variation in the input parameters of the electromagnet, such as the voltage, frequency, and air gap, could be obtained. The force values obtained using the theoretical solution exhibited a satisfactory agreement with the results obtained using the finite element method, thereby demonstrating the validity of the approach. Subsequently, the bowl displacements were analyzed using the motion equation for the bowl feeder when the theoretically obtained excitation force were applied to vibrate the feeder. The correlation between the vertical displacements of the bowl and input parameters of the electromagnet could be obtained.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.29-34
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• 2006

In general, the vertical vibration problems for .strength of members and serviceability of building structures are not considered in structural design process, but the prediction of the vertical vibration is very important and essential to structural design process. This study aims to investigate the characteristics of vertical vibration in terms of the transfer of horizontal directions on the rahmen building structures. In order to examine the characteristics of vertical vibration, the modal test and the impact (heel-drop and hammer) excitation experiments were conducted several times on three building structures. The results from the experiments are analyzed and compared. with the results. The results of this study suggest that the characteristics of vertical vibration transfer in horizontal way are effected from the fundamental frequency of the slabs and excitation forces.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.399-413
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• 2020

The numerical simulation of liquid sloshing in the three-dimensional tanks under horizontal excitation and roll excitation was carried out, and the inhibition effect of different baffles on the sloshing phenomenon was investigated. The numerical calculations were carried out by the nonlinear Boundary Element Method (BEM) with Green's theorem based on the potential flow, which was conducted with the governing equation corresponding to the boundaries of each region. The validity of the method was verified by comparing with experimental values and published literatures. The horizontal baffle, the vertical baffle and the T-shaped baffle in the sloshing tanks were investigated respectively, and the baffles' position, dimension and the liquid depth were provided and discussed in detail. It is drawn that the baffle shape plays a non-negligible role in the tank sloshing. The vertical baffle is a more effective way to reduce the sloshing amplitude when the tank is under a horizontal harmonic excitation while the horizontal baffle is a more effective way when the tank is under a roll excitation. The amplitude of free surface elevation at right tank wall decreases with the increasing of the horizontal baffle length and the vertical baffle height. Although the T-shaped baffle has the best suppression effect on tank sloshing under horizontal excitation, it has limited suppression effect under roll excitation and will complicate the sloshing phenomenon when changing baffle height.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.196-201
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• 2006

In general, the vertical vibration problems for strength of members and serviceability of building structures are not considered in structural design process, but the prediction of the vertical vibration is very important and essential to structural design process. This study aims to investigate the characteristics of vertical vibration in terms of the transfer of horizontal directions on the rahmen building structures and the shear wall building structures. In order to examine the characteristics of vertical vibration, the modal test and the heel-drop excitation experiments were conducted several times on the two type building structures. The results from the experiments are analyzed and compared with the results. The results of this study suggest that the characteristics of vortical vibration transfer in horizontal way are effected from the fundamental frequency of the slabs and excitation forces and are effected the shear wall on the path of the vibration transfer.