• Steel and Composite Structures
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• v.36 no.1
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• pp.17-29
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• 2020

This paper presents experimental and numerical studies on the seismic responses of the steel cabinet facility considering the nonlinear behavior of connections and site-response effects. Three finite element (FE) models with differences of type and number of connections between steel plates and frame members have been developed to demonstrate adequately dynamic responses of structures. The screw connections with the bilinear force-deformation relationship are proposed to represent the inelastic behavior of the cabinet. The experiment is carried out to provide a verification with improved FE models. It shows that the natural frequencies of the cabinet are sensitive to the plate and frame connectors. The screw connections reduce the free vibration compared to the weld one, with decreased values of 2.82% and 4.87% corresponding to front-to-back and side-to-side directions. Additionally, the seismic responses are investigated for various geological configurations. Input time histories are generated so that their response spectrums are compatible with a required response spectrum via the time-domain spectral matching. The results indicate that both site effects and nonlinear behavior of connections affect greatly on the seismic response of structures.

• Earthquakes and Structures
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• v.20 no.4
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• pp.405-415
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• 2021

Following the dynamic property analysis and elaboration, linear response spectrum analysis (RSA) and response history analysis (RHA) were conducted on a representative hyperbolic cooling towers (HCT) in present study. The seismic responses in tower shell were illustrated in detail, including the internal force amplitude, modal contribution, influence from damping ratio, comparison of results got from RSA and RHA and especially the latitude distributions of internal forces. The results show that the eigenmodes could be classified in a new method into four types according to their mode shapes and only the lateral bending modes and vertical stretching modes are meaningful for horizontal and vertical earthquake correspondingly. The bending modes and seismic deformation display the same feature which is global lateral bending accompanied by minute circular flow displacement of section. This feature also decides the latitude distributions of internal forces as sine or cosine. Moreover, the following method is also proposed for approximate estimation of internal force amplitudes without time-consuming response history analysis: getting the response spectrums of the selected ground accelerations and then comparing values of response spectrums at the natural period of first lateral bending mode because it is always prime dominant for horizontal seismic responses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.730-736
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• 2016

In a previous study, the impact factor response spectrum and corresponding method for evaluating the load carrying capacity of bridges was suggested to improve the existing evaluation method. To verify the applicability of the suggested method, which is based on the frequency of bridges, the dynamic characteristic test for an actual single span simply-supported bridge was conducted. Through a field test under ambient traffic conditions, the dynamic response of the bridge was obtained using wireless accelometers and its fundamental frequency was identified. The peak impact factor was determined from the identified frequency and the impact factor response spectrum. The load carrying performance variation of the bridge was estimated considering the performance reduction factor, which was calculated using the current and previous natural frequency and impact factor. From the result, the load carrying capacity of the bridge was decreased, but the capacity was still enough because its value is greater than the design live load. Through the overall procedures and technical details presented in this paper, the suggested evaluation method can be applied to actual bridges with the acceleration data measured under ambient traffic conditions and the impact factor response spectrum.

• Geotechnical Engineering
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• v.13 no.1
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• pp.111-122
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• 1997

The calculation of phase velocities in Spectral-Analysis -of-Surface -Waves (SASW) meas urements requires unwrapping phase angles. In case of layered systems with strong stiffness contrast like a pavement system, conventional phase unwrapping algorithm to add in teger multiples of 2n to the principal value of a phase angle may lead to wrong phase volocities. This is because there is difficulty in counting the number of jumps in the phase spectrum especially at the receiver spacing where the measurements are in the transition Bone of defferent modes. A new phase interpretation scheme, called "Impulse Response Fil traction ( IRF) Technique," is proposed, which is based on the separation of wave groups by the filtration of the impulse response determinded between two receivers. The separation of a wave group is based on the impulse response filtered by using information from Gabor spectrogram, which visualizes the propagation of wave groups at the frequency -time space. The filtered impulse response leads to clear interpretation of phase spectrum, which eliminates difficulty in counting number of jumps in the phase spectrum. Verification of the IRF technique was performed by theoretical simulation of the SASW measurement on a pavement system which complicates wave propagation.opagation.

• Journal of the Korean Geotechnical Society
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• v.38 no.9
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• pp.5-17
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• 2022

Recently, several studies have been conducted on virtual fixed-point and elastic soil spring methods to simulate the soil-pile interaction in response to spectrum analysis of pile-supported structures. However, the soil spring stiffness has not been properly considered due to the seismic load magnitude, and studies on the response spectrum analysis of pile-supported structures considering this circumstance are inadequate. Therefore, in this study, the response spectrum analysis was performed considering the soil spring stiffness according to the seismic load magnitude, and the dynamic behavior of the pile-supported structure was evaluated by comparing it with existing virtual fixed-point and elastic soil spring methods. Comparing the experiment and analysis, the moment differences occurred up to 117% and 21% in the virtual fixed-point and elastic soil spring models, respectively. Moreover, when the analysis was performed using an API p-y curve considering the soil spring stiffness according to the seismic load magnitude, the moment difference between the experiment and analysis was derived at a maximum of < 4%, and it is the most accurate method to simulate the experimental model response.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1192-1207
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• 2014

Dynamic spectrum sharing is a key technology to improve spectrum utilization in wireless networks. The elastic spectrum management provides a new opportunity for licensed primary users and unlicensed secondary users to efficiently utilize the scarce wireless resource. In this paper, we present a game-theoretic framework for dynamic spectrum allocation where the primary users rent the unutilized spectrum to the secondary users for a monetary profit. In reality, due to the ON-OFF behavior of the primary user, the quantity of spectrum that can be opportunistically shared by the secondary users is limited. We model this situation with the renewal theory and formulate the spectrum pricing scheme with the Bertrand game, taking into account the scarcity of the spectrum. By the Nash-equilibrium pricing scheme, each player in the game continually converges to a strategy that maximizes its own profit. We also investigate the impact of several properties, including channel quality and spectrum substitutability. Based on the equilibrium analysis, we finally propose a decentralized algorithm that leads the primary users to the Nash-equilibrium, called DST. The stability of the proposed algorithm in terms of convergence to the Nash equilibrium is also studied.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.477-480
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• 2004

We studied the characteristics of impedance and electromechanical coupling coefficient in ZnO and AIN thin films by using resonance frequency spectrum method. The response peak of impedance decreased with the decrease of thickness of piezoelectrics, the number of mode of response peak increased with the increase of substrate thickness. An error of $k_{t}^{2}$ estimated from input $k_{t}^{2}$ increased as the thickness of piezoelectrics decreased and the thickness of substrate increased. Also, the error was increased in case of a large acoustic impedance of substrate. It was found that the composite resonator operating in optimized condition could be designed through the resonance frequency spectrum analysis of composited resonator consisted of piezoelectric thin film and substrate.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.943-946
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• 1988

A simple method is proposed for determining the frequency response function G(j.omega.) of a system using a pair of characteristic M-sequences (maximum length linear feed back shift register sequence). When a characteristic M-sequence is sampled with q$_{1}$ and q$_{2}$ both of which are coprime with N, where N is the period of the M-sequence, the obtained pair of sequences have conjugate complex frequency spectrum. Making use of this fact, two charcteristic M-sequences having conjugate complex frequency spectrum are applied to a system to be measured. Since the magnitude of spectrium of M-sequence is known, the gain of G(j.omega.) is directly obtained from the Fourier transform of the system output. The phase of G(j.omega.) is obtained simply by taking the average of the two phases of output spectrum.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.4
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• pp.1024-1030
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• 2016

This study gives the vertical motion analysis due to changes in Submerged shape of Multi-Purpose Small Floating Body in irregular waves using the commercial code(MAXSURF v.20) based on the Panel method. To verify the commercial code prior to the analysis, we guarantees the reliability of this paper's results using the commercial code by comparing with the results of experimental results on Catamaran. The anlysis conditions are ITTC wave spectrum, each encounter angle. Finally, we analyze the result of ship's response spectra for vertical motions.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.465-472
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• 2003

In this paper, the displacement-based seismic design approaches are evaluated utilizing shaking-table test data of a 1:3 scaled reinforced concrete (RC) bearing wall structure Provided by IAEA. The maximum responses of the structure are estimated using the two prominent displacement-based approaches, i.e., the capacity spectrum method and the displacement coefficient method, and compared with the measured responses. For comparison purpose, linear and nonlinear time history analyses and response spectrum analysis are also performed. The results indicate that the capacity spectrum method underestimates the response of the structure In inelastic range while the displacement coefficient method yields reasonable values in general.