• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.04a
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• pp.207-214
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• 1997

The objective of this study is to review the current stare of earthquake simulation techniques using the shaking table and check the reliability. One degree-of-freedom(d.o.f.)and three d.o.f. aluminium shear models were used and 4m$\times$4m 6 d.o.f. shaking table was excitated in one horizontal direction to simulate 1940 El centro earthquake accelerogram (NS component). When the acceleration history of shaking table is compared to the desired one, it can be found that the overall histories are very similar, but that the lower frequency range (0~2 Hz) of the actual excitation has generally lower amplitude than that of the desired in fourier transform amplitude. Free vibration and white noise tests have shown almost the same values for natural frequencies, but shown quite different values for damping ratios, that is, 1.37% in case of r\free vibration test vs 14.76% in case of white noise test. The time histories of story shear versus story drift show the globally linear elastic behaviors. But the elliptical shape of the histories with one of the axis being the stiffness of the story implies the effect of viscous damping.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.2_2
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• pp.245-254
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• 2020

This study investigated the so far little-researched characteristics of the behaviors of rock slopes at the time of an earthquake. For the selection of the rock block, a proper model was formed by applying the similarity in consideration of the roughness and strength of the rock slope(10m) on the site, and shaking table tests were carried out according to seismic excitement acceleration, and seismic waves. In the case of the inclination angle of the joint plane of 20°, the long period wave at 0.3g or more at the time of the seismic excitement surpassed the length of 100mm, the permissible displacement (0.01H, H:slope height), which brought about the collapse of the rock; the short period wave surpassed the permissible displacement at 0.1g, which caused the collapse of the slope. The rock slope was close to a rigid block and a structure more vulnerable to the long period wave than to the short period wave. It collapsed in the short period wave even at the seismic amplitude smaller than the maximum design acceleration in Korea.

• Structural Engineering and Mechanics
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• v.19 no.5
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• pp.581-602
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• 2005

In this paper the accumulation of local damage during the cyclic loading in reinforced high-strength concrete columns is experimentally investigated. Two identical column specimens with annular cross-section and spiral reinforcement were designed and two tests, up to failure, under the action of a constant vertical concentrated force and a time-dependent concentrated horizontal force, were carried out at the LNEC shaking tables facility. Sine type signals, controlled in amplitude, frequency and time duration were used for these experiments. The concept of local damage based on local stiffness degradation is considered in detail and illustrated by experimental results. The specimens were designed and reinforced in such a way that the accumulation of damage was predicted by dominating deformations (cracking and crushing of the concrete) while the increasing of the loading values was a dominating factor of damage. It was observed that the local damage of HSC columns has exposed their anisotropic local behaviour. The damage accumulation was slightly different from the expected in accordance with the continuum damage concept, and a partial random character was observed.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.11
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• pp.129-136
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• 2019

Non-structural elements are vulnerable to earthquake ground motion. In this study, an experimental study for the electrical non-structural element was performed using tri-axial shaking table tests. A 100kVA UPS(Uninterruptible Power Supply system) was used as the test specimen. The test specimen was anchored to the concrete slab using the conventional installation detail. The input acceleration were generated in accordance with ICC-ES AC156 code. Scale factors of the input acceleration with respect to the required response spectrum defined in ICC-ES AC156 were from 25% to 600%. Based on the test results, damage and dynamic characteristics of UPS were evaluated and analyzed including natural frequency, damping ratio, acceleration time history response, dynamic amplification factor and relative displacement.

• Smart Structures and Systems
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• v.15 no.3
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• pp.863-879
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• 2015

This paper experimentally investigates the effectiveness and applicability of the time delay control (TDC) algorithm, which is simple and robust to unknown system dynamics and disturbance, for an active mass damper (AMD) system to mitigate the excessive vibration of a building structure. To this end, the theoretical background including the mathematical formulation of the control system is first described; and then, a thorough experimental study using a shaking table system with a small-scale three-story building structural model is conducted. In the experimental tests, the performance of the proposed control system is examined by comparing its structural responses with those of the uncontrolled system in the free vibration and forced vibration cases. It is clearly verified from the test results that the TDC algorithm embedded AMD system can effectively reduce the structural response of the building structure.

• Preventive Nutrition and Food Science
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• v.20 no.2
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• pp.119-125
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• 2015

The biologically active compounds raphasatin and sulforaphene are formed during the hydrolysis of radishes by an endogenous myrosinase. Raphasatin is very unstable, and it is generated and simultaneously degraded to less active compounds during hydrolysis in aqueous media. This study determined the hydrolysis conditions to maximize the formation of raphasatin and sulforaphene by an endogenous myrosinase and minimize their degradation during the hydrolysis of radish roots. The reaction parameters, such as the reaction medium, reaction time, type of mixing, and reaction temperature were optimized. A stability test for raphasatin and sulforaphene was also performed during storage of the hydrolyzed products at $25^{\circ}C$ for 10 days. The formation and breakdown of raphasatin and sulforaphene in radish roots by endogenous enzymolysis was strongly influenced by the reaction medium, reaction time, and type of mixing. The production and stabilization of raphasatin in radishes was efficient in water and dichloromethane with shaking for 15 min at $25^{\circ}C$. For sulforaphene, the favorable condition was water as the reaction medium without shaking for 10 min at $25^{\circ}C$. The maximum yields of raphasatin and sulforaphene were achieved in a concurrent hydrolysis reaction without shaking in water for 10 min and then with shaking in dichloromethane for 15 min at $25^{\circ}C$. Under these conditions, the yields of raphasatin and sulforaphene were maximized at 12.89 and $1.93{\mu}mol/g$ of dry radish, respectively. The stabilities of raphasatin and sulforaphene in the hydrolyzed products were 56.4% and 86.5% after 10 days of storage in water and dichloromethane at $25^{\circ}C$.

• Structural Engineering and Mechanics
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• v.83 no.1
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• pp.93-108
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• 2022

Real-time hybrid simulation (RTHS) was applied to investigate the train-bridge interaction of a high-speed railway system, where the railway bridge was selected as the numerical substructure, and the train was physically tested. The interaction between the two substructures was reproduced by a servo-hydraulic shaking table. To accurately reproduce the high-frequency interaction responses ranging from 10-25Hz using the hydraulic shaking table with an inherent delay of 6-50ms, an adaptive time series (ATS) compensation algorithm combined with the linear quadratic Gaussian (LQG) was proposed and implemented in the RTHS. Testing cases considering different train speeds, track irregularities, bridge girder cross-sections, and track settlements featuring a wide range of frequency contents were conducted. The performance of the proposed ATS+LQG delay compensation method was compared to the ATS method and RTHS without any compensation in terms of residual time delays and root mean square errors between commands and responses. The effectiveness of the ATS+LQG method to compensate time delay in RTHS with high-frequency responses was demonstrated and the proposed ATS+LQG method outperformed the ATS method in yielding more accurate responses with less residual time delays.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.1
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• pp.51-56
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• 1997

The objective of this study is to review the current state of earthquake simulation tecniques using the shaking table and check the reliability. One degree-of-freedom(d.o.f) and three d.o.f aluminium shear models were used and $4m{\times}4m$ 6 d.o.f shaking table was excitated in one horizontal direction to simulate 1940 El centro earthquake accelerogram (NS component). When the actual acceleration history of shaking table is compared to the desired one, it can be found that the overall histories are very similar, but that the lower frequency range (0~2 Hz) of the actual excitation has generally lower amplitude than that of the desired in Fourier transform amplitude. Free vibration and white noise tests have shown almost the some values for natural frequencies, but shown quite different values for damping rations, that is, 1.37% in case of free vibration test vs 14.76 % in case of white noise test. The time histories of story shear driff show the globally linear elastic behaviors. But the elliptical shape of the histories with one of the axis being the stiffness of the story implies the effect of viscous damping.

• Journal of the Korean Geotechnical Society
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• v.20 no.9
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• pp.91-103
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• 2004

A series of shaking table model tests were performed to verify the validity of similitude law, which is suggested by lai (1989) to simulate the dynamic behavior of soil-fluid-structure system for is shaking table tests. In the tests, the similitude law suggested by lai was applied to determine the length and the time scaling factors. Also, the steady state concept was used in determining the density of model backfill soil, which is a key factor in simulating the development of excess pore pressure during shaking. The similitude law was verified by checking whether three different sizes of quay walls show the identical behavior or not. The similar responses of acceleration, excess pore pressure and horizontal displacement of walls were obtained far the small and large models. However, the medium model showed larger responses than those of the small and large models because of the resonance between the frequency of input acceleration and the natural frequency of the wall system. In addition, the vertical displacement and rotational angle of the walls became larger with the increase of model size.

• Earthquakes and Structures
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• v.23 no.2
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• pp.169-181
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• 2022

To research the dynamic response of the high-rise structure under the rocking ground motion, which we believed that the effect cannot be ignored, especially accompanied by vertical ground motion. Theoretical analysis and shaking table seismic simulation tests were used to study the response of a high-rise structure to excitation of a H-V-R ground motion that included horizontal, vertical, and rocking components. The use of a wavelet analysis filtering technique to extract the rocking component from data for the primary horizontal component in the first part, based on the principle of horizontal pendulum seismogram and the use of a wavelet analysis filtering technique. The dynamic equation of motion for a high-rise structure under H-V-R ground motion was developed in the second part, with extra P-△ effect due to ground rocking displacement was included in the external load excitation terms of the equation of motion, and the influence of the vertical component on the high-rise structure P-△ effect was also included. Shaking table tests were performed for H-V-R ground motion using a scale model of a high-rise TV tower structure in the third part, while the results of the shaking table tests and theoretical calculation were compared in the last part, and the following conclusions were made. The results of the shaking table test were consistent with the theoretical calculation results, which verified the accuracy of the theoretical analysis. The rocking component of ground motion significantly increased the displacement of the structure and caused an asymmetric displacement of the structure. Thus, the seismic design of an engineering structure should consider the additional P-△ effect due to the rocking component. Moreover, introducing the vertical component caused the geometric stiffness of the structure to change with time, and the influence of the rocking component on the structure was amplified due to this effect.