• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.86-93
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• 2002

In this study, numerical experiments were performed to decide the proper size off finite element for the analysis of harbor resonance problems. Various sizes of finite elements were considered from 1/3 to 1/60 of wavelength to model a fully opened rectangular harbor. Through the numerical results, the proper number of finite elements per wavelength were revealed to be nine within two percents errors allowed in resonant period and amplification ratio, while twelve within one percent error. It was fecund that error rates of resonant periods decrease linearly, while those of amplification ratio decrease with oscillating form as the size of an element decreases. The error of amplification ratio increases more rapidly than that of resonant period in case of element numbers below nine.

• Journal of the Korean earth science society
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• v.30 no.7
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• pp.810-823
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• 2009

One of the critical factors in accurate determination of earthquake source parameters, and in prediction of seismic hazards is the detailed information related to the site amplification characteristics. The site amplification characteristics of the broad-band seismic stations in Korea were estimated as a function of frequency in the range of 0.2 to 20 Hz. A total of 1275 seismograms recorded from 43 earthquakes observed from 2003 to 2008 in the southern Korean Peninsula were used. It was found that the site amplification ratios for 28 stations estimated from the inversion of the ground motion model were approximately concordant with those obtained from the horizontal-to-vertical (H/V) spectral ratio except for some stations. The spectral site amplification characteristics obtained in this study did not show any considerable spatial distribution. It revealed to be largely correlated with the degree of weathering rather than the basement rock type. Considering the spectral site amplification ratio, 28 broad-band stations were classified into four groups and the characteristics of each group were described in the text.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.2
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• pp.1-12
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• 2000

단층에 근접한 지진동에 대하여 성능이 저하되는 단자유도계의 변위응답에 대하여 연구하였다 5% 의 감쇠비를 갖는 세단계의 성능저하시스템을 5개의 단층에 근접한 지진동에 대하여 해석하였다 해석결과로부터 성능저하시스템의 비탄성 변위응답은 비저하시스템에 비하여 큰 값을 나타냄을 알 수 있었다 또한 성능저하 특성이 증가할수록 변위응답은 커지는 경향이 있다 이러한 변위증폭은 구조물의 고유주기 강도와 성능저하특성에 영향을 받으며 짧은 주기영역에서는 큰 값을 나타내며 긴 주기영역에서는 변위증폭이 거의 발생하지 않는다 단층에 근접한 각각의 지진동에 대한 변위증폭의 최대값은 1초 보다 작은 주기영역에서 비저하시스템의 4배 정도이다 변위증폭계수의 평균값은 짧은 주기영역에서는 2의 값을 가지면 구조물의 고유주기가 길어질수록 1에 수렴해 감을 알 수 있었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.6
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• pp.67-74
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• 2010

Because of the difference between the actual and computed eccentricity of buildings, symmetrical buildings will be affected by torsion. In provisions, accidental eccentricity is intended to cover the effect of several factors, such as unfavorable distributions of dead- and live-load masses and the rotational component of ground motion about a vertical axis. The torsional amplification factor is introduced to reduce the vulnerability of torsionally imbalanced buildings. The effect of the torsional amplification factor is observed for a symmetric rectangular building with various aspect ratios, where the seismic-force-resisting elements are positioned at a variable distance from the geometrical center in each direction. For verifying the torsional amplification factor in provisions, nonlinear reinforced concrete models with various eccentricities and aspect ratios are used in rock. The difference between the maximum displacements of the flexible edge obtained between using nonlinear static and time-history analysis is very small but the difference between the maximum torsional angles is large.

• Tunnel and Underground Space
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• v.16 no.6 s.65
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• pp.486-494
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• 2006

The horizontal to vertical (H/V) ratio technique in spectral domain is a common useful technique to estimate empirical site transfer function. The technique, originally proposed by Nakamura, is proposed to analyse the surface waves in the micrortremor records. The purpose of this paper is to estimate spectral ratio using observed data at the seismic stations distributed within Southern Korean Peninsula from the Fukuoka earthquake including 11 aftershocks. The results show that most of the stations have fairly good amplification characteristics in low frequency band. However, some of the seismic stations show one (resonant frequency specific to the site) or several local peaks of amplification factors with narrow high frequency band. Even though the site amplification characteristics are important information, we should be careful to analyse the observed ground motions from the seismic stations which have several very high amplification peaks for the deconvolution of seismic source and attenuation parameters.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.205-206
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• 2009

This study deals with the viscoelastic damper system with displacement-amplification unit (DAU) which can maximize the effectiveness of a damper system in controlling seismic response of a building by amplifying story drift induced to damper. DAUs in this study were analyzed to be able to amplify the displacement 2 to 4 times greater than the original story drift. The efficiency of each DAU was expressed by $\beta$ (DAU ratio) and examined in this analytical study.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.507-510
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• 2001

A numerical analysis based on the nonlinear Schroedinger equation is presented to analyze the propagation stability of the average soliton in a simple nonlinear amplifying loop mirror. The ratio of amplification period to soliton period and the length fraction of the erbium-doped fiber in the loop are varied to investigate their effects on the soliton stability. It is observed that stable soliton propagation is obtained even when the amplification period is only slightly shorter than the soliton period when the length fraction of the erbium-doped fiber in the loop is small, which is different from the previously published condition for stable average soliton propagation.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.1
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• pp.27-34
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• 2009

Site amplification should be considered in order to estimate Soil-Structure Interaction (SSI), seismic source and attenuation parameters with a greater degree of reliability. The horizontal to vertical (H/V) ratio technique, originally proposed by Nakamura (1989), has been applied to analyze the surface waves in microtremor records. Recently, its application has been extended to the shear wave energy of strong motion in order to study the site transfer function. The purpose of this paper is to estimate the H/V spectral ratio using the observed data from 9 seismic stations distributed within the Southern Korean Peninsula, from the Odesan earthquake (2007/01/20). The results show that most of the stations have more stable amplification characteristics in a low frequency band than in a high frequency band. However, each seismic station showed its own characteristic resonant frequency and low and high frequency. The resonant frequency at each station should be estimated carefully, because the quality of seismic data is dependent on the resonant frequency. It can be obtained more reliable results of seismic source and attenuation parameters, if seismic ground motions which deconvolved from site transfer function is used. The site amplification data from this study can be used to generally classify the sites within the Southern Korean Peninsula.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.267-268
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• 2013

본 논문에서는 아날로그 필터회로의 신호 증폭비에 따른 센서리스 각추정 성능에 대해 분석 하였다. 신호 주입 센서리스에서 높은 주파수 신호 주입 방법이 선호되는데, 주입 주파수가 커질수록 시스템 임피던스가 증가한다. 따라서 낮은 주파수 주입방법과 동일한 각추정 성능을 얻기 위해서는 상대적으로 큰 주입전압이 필요하다. 특히 전동기의 돌극성이 작거나 ADC의 정밀도가 낮으면 각추정이 불가능한 경우도 존재 한다. 하지만 아날로그 필터회로를 이용하여 주입 주파수 신호를 증폭할 경우 작은 크기의 전압주입으로 각추정이 가능하다. 아날로그 대역통과필터의 신호 증폭비에 따른 최대 각에러 값을 모의 실험을 통해 비교하고, 실제 회로를 설계하여 센서리스 각추정 성능을 시험평가 하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.454-457
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• 2011

본 논문에서는 국내에서 아직 기준이 마련되지 않은 제진설계에 대한 접근을 소개하였다. ASCE 7-05 기준에 근거하여 국내 5층 규모의 철근콘크리트 신축 건물에 제진 설계를 수행하였다. 우리나라의 현행 기준을 만족하면서 효과적인 제진 시스템 설계를 위한 방법을 소개한다. ASCE 7-05 기준에서는 제진 구조물 해석 시 부재력이 공칭강도의 1.5배를 초과하지 않은 경우 경계비선형 해석을 허용하고 있다. 이 때의 제진 설계 프로세스는 기존의 중력하중 및 등가정적하중의 75%에 의한 단면을 가정하여 부재설계를 실시하고, 선형 시간이력 해석을 통해 제진장치 및 가새를 설계한다. 이후 우리나라 실정에 맞도록 보정된 인공 지진파를 입력하여 경계비선형 해석을 실시하고, 밑면 전단력 및 층간변위 등의 만족여부를 검토한다. 이 때 목표성능을 완전탄성설계 또는 유사탄성설계로 정하여 목표성능을 만족하는지도 검토하여야 한다. 본 논문에 적용한 신축 건물은 유사탄성 설계를 위해 경계비선형 해석을 실시하였고, 가장 효과적인 제진 설계를 위해 댐퍼의 종류, 설치방법, 개수, 변위 증폭비 등을 변수로 한 case study를 진행하였다. 해석 결과 목표성능을 만족하는 범위 내에서 가장 효과적인 제진 설계는 점성댐퍼, 이층 토글형태, 증폭비 2.0, 총 8개의 댐퍼를 설치하는 것으로 나타났다.