• Earthquakes and Structures
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• 제13권2호
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• pp.193-200
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• 2017

To overcome the difficulty of performing multi-point response spectrum analysis for engineering structures under spatially varying ground motions (SVGM) using the general finite element code such as ANSYS, an approach has been developed by improving the modelling of the input ground motions in the spectral analysis. Based on the stochastic vibration analyses, the cross-power spectral density (c-PSD) matrix is adopted to model the stationary SVGM. The design response spectra are converted into the corresponding PSD model with appropriate coherency functions and apparent wave velocities. Then elements of c-PSD matrix are summarized in the row and the PSD matrix is transformed into the response spectra for a general spectral analysis. A long-span high-pier bridge under multiple support excitations is analyzed using the proposed approach considering the incoherence, wave-passage and site-response effects. The proposed approach is deemed to be an efficient numerical method that can be used for seismic analysis of large engineering structures under SVGM.

• 한국지반공학회논문집
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• 제24권8호
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• pp.137-148
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• 2008

본 연구에서는 국내 항만 및 어항시설의 내진설계표준서에서 설계 예로 이용한 지진파를 포함하여 지진규모 $5.3{\sim}7.9$ 수준의 28개의 지진기록에 대한 에너지와 스펙트럼 분석을 통한 국내 적합성 여부를 평가하였고, 이를 통해 국내 내진설계에 적용 가능한 입력지진기록을 제안하였다. 그리고 제안된 지진기록을 이용하여 케이슨의 형상 및 하부지반 상태에 따른 케이슨 안벽의 동적 수평변위특성을 분석하였다. 연구 결과 지진파가 보유하고 있는 에너지와 가속도 스펙트럼의 크기는 지진규모가 커질수록 증가하였다. 특히, 지진규모 7.5 부근의 지진기록은 내진설계기준에 규정된 표준설계응답스펙트럼에서 크게 벗어난 반면, 지진규모 6.5 부근의 4개의 지진기록은 국내 내진설계기준에 규정된 표준설계응답스펙트럼을 거의 만족하는 것으로 나타났다. 그리고, 입력지진에 따른 케이슨 안벽의 동적 수평변위특성 분석 결과 국내 항만 및 어항시설의 내진설계 표준서의 예제로 제시한 지진규모 7.4 이상의 지진파의 수평변위는 국내의 내진설계기준에서 제시한 표준설계응답스펙트럼을 대체적으로 만족하는 지진규모 6.5 수준의 지진파의 수평변위보다 2배 이상 크게 나타났다. 이러한 결과로부터 지진규모 7.4 이상의 지진파를 이용한 내진설계는 지진력을 과다하게 산정하여 비경제적인 설계를 할 수 있음을 알 수 있었다. 국내 적합성 평가로부터 구한4개의 지진기록을 입력하중으로한 동해석 결과에 대한 정량적인 분석을 통해 케이슨의 형상과 하부지반 깊이 및 지반의 표준관입저항치를 이용하여 간편하게 케이슨 안벽의 지진시 수평변위를 산정할 수 있는 간편도표를 제안하였다.

• Structural Engineering and Mechanics
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• 제42권1호
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• pp.121-129
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• 2012

All contemporary seismic Codes have adopted smooth design acceleration response spectra, which have derived by statistical analysis of many elastic response spectra of natural accelerograms. The above smooth design spectra are characterized by two main branches, an horizontal branch that is 2.5 times higher than the peak ground acceleration, and a declining parabolic branch. According to Eurocode EN/1998, the period range of the horizontal, flat branch is extended from 0.1 s, for rock soils, up to 0.8 s for softer ones. However, from many natural recorded accelerograms of important earthquakes, the real spectral amplification factor appears to be much higher than 2.5 and this means that the spectrum leads to an unsafe seismic design of the structures. This point is an issue open to question and it is the object of the present study. In the present paper, the spectral amplification factor of the smooth design acceleration spectra is re-calculated on the grounds of a known "reliability index" for a desired probability of exceedance. As a pilot scheme, the seismic area of Greece is chosen, as it is the most seismically hazardous area in Europe. The accelerograms of the 82 most important earthquakes, which have occurred in Greece during the last 38 years, are used. The soil categories are taken into account according to EN/1998. The results that have been concluded from these data are compared with the results obtained from other strong earthquakes reported in the World literature.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.440-447
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• 2000

In order to evaluate the cost effectiveness of seismic isolation for bridges in low and moderate seismic region, a method of calculation minimum life-cycle cost of seismic-isolated bridges under specific acceleration level and soil condition is developed. Input ground motion is modeled as spectral density function compatible with response spectrum for combination of acceleration coefficient and site coefficient. Failure probability is calculated by spectrum analysis based on random vibration theories to simplify repetitive calculations in the minimization procedure. Ductility of piers and its effects on cost effectiveness are considered by stochastic linearization method. Cost function and cost effectiveness index are defined by taking into consideration the characteristics of seismic isolated bridges. Limit states for calculation of failure probability are defined on superstructure, isolator and pier, respectively. The results of example design and analysis show that seismic isolation is more cost-effective in low and moderate seismic region than in high seismic region.

• 전산구조공학
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• 제6권2호
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• pp.79-86
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• 1993

원자력발전소중 안전과 관련된 구조물은 지진의 가능성에 대비하여 그의 구조적 안전성과 가용성이 검증되어야 한다. 본 논문은 원자력발전소 보호시스템 캐비넷을 예를 들어 그에 대한 내진검증 방법을 보였다 캐비넷의 유한요소모델을 작성하여 동특성을 구하였고 그 모우드값을 입력지진스펙트럼과 비교한 결과 구조물의 1차 모우드가 입력 스펙트럼의 peak와 일치함으로써 설계변경의 필요성이 대두되었다. 이 peak값을 피하기 위하여 캐비넷의 구조를 변경하였고 변경된 구조물에 대하여 응답스펙트럼해석과 시간이력해석을 수행하여 구조적 건전성과 가용성을 보임으로써 설계변경된 캐비넷의 내진검증을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.731-736
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• 2011

In this study, the safety of the driving gear reducer of ESW traveling sea water screen was evaluated through seismic analysis. Mode analysis of gear reducer was performed for reliability of analysis. Seismic analysis was performed in Operating Basis Earthquake(OBE) and Safe Shutdown Earthquake(SSE), which was applied as design condition using Floor Respnse Spectrum(FRS). The maxsimum displacement of gear reducer under OBE and SSE were 0.0137 mm and 0.0241 mm, respectively. The maximum stress of gear reducer under OBE and SSE were 2.42 MPa and 4.36 MPa, respectively.

• 대한의용생체공학회:의공학회지
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• 제10권2호
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• pp.83-88
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• 1989

This paper is a study on the design of adptive filter for QRS complex detection. We propose a simple adaptive algorithm to increase capability of noise cancelation in QRS complex detection with two stage adaptive filter. At the first stage, background noise is removed and at the next stage, only spectrum of QRS complex components is passed. Two adaptive filters can afford to keep track of the changes of both noise and QRS complex. Each adaptive filter consists of prediction error filter and FIR filter The impulse response of FIR filter uses coefficients of prediction error filter. The detection rates for 105 and 108 of MIT/BIH data base were 99.3% and 97.4% respectively.

• 한국기계가공학회지
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• 제5권1호
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• pp.39-44
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• 2006

Ultra precision positioning mechanism has been widely used on semiconductor manufacturing equipments, optical spectrum analyzers and cell manipulations. Ultra precision positioning mechanism consists of several actuators, sensors, guides and control systems. Its efficiency depends on each performance of components. The object of this study is to design and analyze the micro stage that is one of the equipments embodied in ultra precision positioning mechanism. The micro stage consists of PZT actuators and flexure hinges. The structural design of flexure hinge is optimized by using RSM and FEM. The control factors concerned with the design of flexure hinges of stage and arms are optimized by minimizing the equivalent stress on the hinge and maximizing 1st natural frequency based on RSM and FEM simulation under various kinds of design conditions.

• 한국공간구조학회논문집
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• 제15권3호
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• pp.51-60
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• 2015

Recently, the concept of damped outrigger system has been proposed for tall buildings. But, structural characteristics and design method of this system were not sufficiently investigated to date. In this study, the dynamic response control performance of outrigger damper has been analyzed. To this end, a simplified analysis model with outrigger damper system has been developed. An artificial wind of 1000 seconds with 0.1 second time steps was generated by using a Kaimal spectrum. Analysis results show that outrigger damper system is more effective up to 20-23% in the control of dynamic response compared to conventional outrigger system. The increase of outrigger damper capacity usually results in the improved control performance. However, it is necessary to select that proper stiffness and damping values of the outrigger damper system because, the outrigger damper having large capacity is result in heavy financial burden.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1345-1356
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• 2021

Damage to nuclear power plants causes human casualties and environmental disasters. There are electrical facilities that control safety-related devices in nuclear power plants, and seismic performance is required for them. The 2016 Gyeongju earthquake had many high-frequency components. Therefore, there is a high possibility that an earthquake involving many high frequency components will occur in South Korea. As such, it is necessary to examine the safety of nuclear power plants against an earthquake with many high-frequency components. In this study, the shaking table test of electrical facilities was conducted against the design earthquake for nuclear power plants with a large low-frequency components and an earthquake with a large high-frequency components. The response characteristics of the earthquake with a large high-frequency components were identified by deriving the amplification factors of the response through the shaking table test. In addition, safety of electrical facility against the two aforementioned types of earthquakes with different seismic characteristics was confirmed through limit-state seismic tests. The electrical facility that was performed to the shaking table test in this study was a motor control center (MCC).