• Title/Summary/Keyword: spectrum acceleration

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Study on the Improvement of Response Spectrum Analysis of Pile-supported Wharf with Virtual Fixed Point (가상고정점기법이 적용된 잔교식 구조물의 응답스펙트 럼해석법 개선사항 도출 연구)

  • Yun, Jung Won;Han, Jin Tae
    • Journal of the Earthquake Engineering Society of Korea
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    • v.22 no.6
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    • pp.311-322
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    • 2018
  • As a method of seismic-design for pile-supported wharves, equivalent static analysis, response spectrum analysis, and time history analysis method are applied. Among them, the response spectrum analysis is widely used to obtain the maximum response of a structure. Because the ground is not modeled in the response spectrum analysis of pile-supported wharves, the amplified input ground acceleration should be calculated by ground classification or seismic response analysis. However, it is difficult to calculate the input ground acceleration through ground classification because the pile-supported wharf is build on inclined ground, the methods to calculate the input ground acceleration proposed in the standards are different. Therefore, in this study, the dynamic centrifuge model tests and the response spectrum analysis were carried out to calculate the appropriate input ground acceleration. The pile moment in response spectrum analysis and the dynamic centrifuge model tests were compared. As a result of comparison, it was shown that the response spectrum analysis results using the amplified acceleration in the ground surface were appropriate.

DIFFUSIVE SHOCK ACCELERATION BY MULTIPLE WEAK SHOCKS

  • Kang, Hyesung
    • Journal of The Korean Astronomical Society
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    • v.54 no.3
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    • pp.103-112
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    • 2021
  • The intracluster medium (ICM) is expected to experience on average about three passages of weak shocks with low sonic Mach numbers, M ≲ 3, during the formation of galaxy clusters. Both protons and electrons could be accelerated to become high energy cosmic rays (CRs) at such ICM shocks via diffusive shock acceleration (DSA). We examine the effects of DSA by multiple shocks on the spectrum of accelerated CRs by including in situ injection/acceleration at each shock, followed by repeated re-acceleration at successive shocks in the test-particle regime. For simplicity, the accelerated particles are assumed to undergo adiabatic decompression without energy loss and escape from the system, before they encounter subsequent shocks. We show that in general the CR spectrum is flattened by multiple shock passages, compared to a single episode of DSA, and that the acceleration efficiency increases with successive shock passages. However, the decompression due to the expansion of shocks into the cluster outskirts may reduce the amplification and flattening of the CR spectrum by multiple shock passages. The final CR spectrum behind the last shock is determined by the accumulated effects of repeated re-acceleration by all previous shocks, but it is relatively insensitive to the ordering of the shock Mach numbers. Thus multiple passages of shocks may cause the slope of the CR spectrum to deviate from the canonical DSA power-law slope of the current shock.

Diagnosis of Chatter Vibration using Frequency Domain in a Milling Process (밀링 공정시 주파수 영역을 이용한 채터 진동의 진단)

  • 김문기
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.10 no.3
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    • pp.12-18
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    • 2001
  • Frequency domain has been used to detect chatter vibration and to decide commencing point of chatter for the milling processes. For this, power spectrum of accelerations signal is analyzed in the frequency domain. Also, the power spectrum and surface roughness are measured, compared, and evaluated according to the depth of cut by experimental works. As a results, it is known that the commencing point of chatter can be decided the behavior of the maximum amplitude of the power spectrum of acceleration signal and there is a correlation between the power spectrum of acceleration signal and the surface roughness. In conclusion, the power spectrum of acceleration signal can be used as a useful information for detec-tion and estimation of chatter vibration in machining.

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Comparative Analysis of Policies to Vitalize Spectrum Sharing Ecosystem using System Dynamics (시스템 다이내믹스를 이용한 주파수 공유 생태계 활성화 정책대안 비교 분석 연구)

  • Song, Hee Seok;Kim, Jae Kyung;Kim, Taehan
    • Journal of Information Technology Applications and Management
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    • v.21 no.4_spc
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    • pp.431-447
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    • 2014
  • Demand of spectrum resource is tremendously increasing and this trend will continue as more IT services such as cloud computing, smart devices, Internet of Things are provided through wireless network. Recent development of spectrum sharing technology has drawn attention to spectrum policy makers as a promising way to overcome the expected spectrum shortage problem. However, technology-based solution to spectrum shortage problem may not be sustainable since the solution affect only one aspect of spectrum sharing ecosystem. To understand the whole picture of spectrum shortage problem, policies to vitalize spectrum sharing ecosystem were proposed based on the analysis of System Dynamics causal map in the previous study. This study compares and analyzes the effect of those proposed vitalization policies by using System Dynamics simulation. Among seven alternative policies, combined application of demand acceleration policy and technology development policy was found to be more effective for better utilization of spectrum. The effect of demand acceleration policy was offset when other policies are applied together except supply acceleration policy which shows better spectrum sharing.

Firing Shock Measurement and Shock Response Spectrum Analysis of Small Arms (소구경 화기의 사격충격 측정 및 충격응답스펙트럼 분석)

  • Lee, Joon-Ho;Choe, Eui-Jung;Yoon, Joo-Hong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.04a
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    • pp.588-593
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    • 2012
  • Nowadays, various forms of electro-optical rifle scope have been developed and used in order to enhance the accuracy of small arms. However, firing shock acceleration has characteristics of pyroshock having a big acceleration value with very short duration time, which the electro-optical scopes should be designed to sustain. In this paper, the firing shock acceleration, which is transmitted to the electro-optical scope, was measured and SRS (Shock Response Spectrum) analysis was performed by using the measured firing shock acceleration. Furthermore, a shock test condition using a drop-table shock tester, which can simulate the actual firing shock acceleration, was devised. The devised shock test condition will be utilized to test the electro-optical scope itself before attaching it to the small arms.

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A Study on Evaluation of Floor Response Spectrum for Seismic Design of Non-Structural Components (비구조요소의 내진 설계를 위한 기존 층응답스펙트럼의 평가)

  • Choi, Kyung Suk;Yi, Waon Ho;Yang, Won-Jik;Kim, Hyung Joon
    • Journal of the Earthquake Engineering Society of Korea
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    • v.17 no.6
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    • pp.279-291
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    • 2013
  • The seismic damage of non-structural components, such as communication facilities, causes direct economic losses as well as indirect losses which result from social chaos occurring with downtime of communication and financial management network systems. The current Korean seismic code, KBC2009, prescribes the design criteria and requirements of non-structural components based on their elastic response. However, it is difficult for KBC to reflect the dynamic characteristics of structures where non-structural components exist. In this study, both linear and nonlinear time history analyses of structures with various analysis parameters were carried out and floor acceleration spectra obtained from analyses were compared with both ground acceleration spectra used for input records of the analyses and the design floor acceleration spectrum proposed by National Radio Research Agency. Also, this study investigates to find out the influence of structural dynamic characteristics on the floor acceleration spectra. The analysis results show that the acceleration amplification is observed due to the resonance phenomenon and such amplification increases with the increase of building heights and with the decrease of structure's energy dissipation capacities.

Effect of design spectral shape on inelastic response of RC frames subjected to spectrum matched ground motions

  • Ucar, Taner;Merter, Onur
    • Structural Engineering and Mechanics
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    • v.69 no.3
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    • pp.293-306
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    • 2019
  • In current seismic design codes, various elastic design acceleration spectra are defined considering different seismological and soil characteristics and are widely used tool for calculation of seismic loads acting on structures. Response spectrum analyses directly use the elastic design acceleration spectra whereas time history analyses use acceleration records of earthquakes whose acceleration spectra fit the design spectra of seismic codes. Due to the fact that obtaining coherent structural response quantities with the seismic design code considerations is a desired circumstance in dynamic analyses, the response spectra of earthquake records used in time history analyses had better fit to the design acceleration spectra of seismic codes. This paper evaluates structural response distributions of multi-story reinforced concrete frames obtained from nonlinear time history analyses which are performed by using the scaled earthquake records compatible with various elastic design spectra. Time domain scaling procedure is used while processing the response spectrum of real accelerograms to fit the design acceleration spectra. The elastic acceleration design spectra of Turkish Seismic Design Code 2007, Uniform Building Code 1997 and Eurocode 8 are considered as target spectra in the scaling procedure. Soil classes in different seismic codes are appropriately matched up with each other according to $V_{S30}$ values. The maximum roof displacements and the total base shears of considered frame structures are determined from nonlinear time history analyses using the scaled earthquake records and the results are presented by graphs and tables. Coherent structural response quantities reflecting the influence of elastic design spectra of various seismic codes are obtained.

Study on Improvement of Response Spectrum Analysis of Pile-supported Structure: Focusing on the Natural Periods and Input Ground Acceleration (잔교식 구조물의 응답스펙트럼 해석법 개선사항 도출 연구: 고유주기 및 입력지반가속도를 중점으로)

  • Yun, Jung-Won;Han, Jin-Tae;Kim, Jong-Kwan
    • Journal of the Korean Geotechnical Society
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    • v.36 no.6
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    • pp.17-34
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    • 2020
  • In response spectrum analysis of pile-supported structure, an amplified seismic wave should be used as the input ground acceleration through the site-response analysis. However, each design standard uses different input ground acceleration criteria, which leads to confusion in determining the appropriate input ground acceleration. In this study, the ground accelerations were calculated through dynamic centrifuge model test, and the response spectrum analysis was performed using the calculated ground acceleration. Then, the moments derived from the test and analysis were compared, and a method for determining the appropriate input ground acceleration in response spectrum analysis was presented. Comparison of the experimental and simulated results reveals that modeling of the ground using elastic springs allows proper simulation of the natural period of the structure, and the use of a seismic wave that is amplified at the ground surface as the input ground acceleration provided the most accurate results for the response analysis of pile-supported structures in sands.

A Study On Arbitrary Artificial Earthquake Acceleration Generation -Based On Design Response Spectrum of Arbitrary Damping Value- (임의의 인공지진 가속도 발생에 관한 연구 -설계응답 스펙트럼에 기초하여 -)

  • 우운택;김영문;노재선
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1989.04a
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    • pp.5-10
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    • 1989
  • In this study, the basic concept of design response spectrum is briefly revi-ewed. To generate the artificial earthquake acceleration, the method of superpo-sition of cosine waves is used. Theoretical developments using F.F.T. and spect-ral density function are compared. The amplitude was derived by use of the peak factor and the phase angle is d-erived by use of Monte Carlo simulation. To smoothen the match, the calculated pseudo velocity respon-se spectrum is compared with input pseudo velocity response spectrum at a set of control frequencies. With the modified spectral density function, a new acceleration and pseudo velocity response spectrum are generat-ed.

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Design-oriented acceleration response spectrum for ground vibrations caused by collapse of large-scale cooling towers in NPPs

  • Lin, Feng;Jiang, Wenming
    • Nuclear Engineering and Technology
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    • v.50 no.8
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    • pp.1402-1411
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    • 2018
  • Nuclear-related facilities can be detrimentally affected by ground vibrations due to the collapse of adjacent cooling towers in nuclear power plants. To reduce this hazard risk, a design-oriented acceleration response spectrum (ARS) was proposed to predict the dynamic responses of nuclear-related facilities subjected to ground vibrations. For this purpose, 20 computational cases were performed based on cooling tower-soil numerical models developed in previous studies. This resulted in about 2664 ground vibration records to build a basic database and five complementary databases with consideration of primary factors that influence ground vibrations. Afterwards, these databases were applied to generate the design-oriented ARS using a response spectrum analysis approach. The proposed design-oriented ARS covers a wide range of natural periods up to 6 s and consists of an ascending portion, a plateau, and two connected descending portions. Spectral parameters were formulated based on statistical analysis. The spectrum was verified by comparing the representative acceleration magnitudes obtained from the design-oriented ARS with those from computational cases using cooling tower-soil numerical models with reasonable consistency.