• Nuclear Engineering and Technology
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• 제48권3호
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• pp.831-839
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• 2016

Seismic qualification by test is widely used as a way to show the integrity and functionality of equipment that is related to the overall safety of nuclear power plants. Another means of seismic qualification is by direct integration analysis. Both approaches require a series of time histories as an input. However, in most cases, the possibility of using real earthquake data is limited. Thus, artificial time histories are widely used instead. In many cases, however, response spectra are given. Thus, most of the artificial time histories are generated from the given response spectra. Obtaining the response spectrum from a given time history is straightforward. However, the procedure for generating artificial time histories from a given response spectrum is difficult and complex to understand. Thus, this paper presents a simple time-domain method for generating a time history from a given response spectrum; the method was shown to satisfy conditions derived from nuclear regulatory guidance.

• Structural Engineering and Mechanics
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• 제64권4호
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• pp.473-485
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• 2017

An isolated building, composed of superstructure and isolation system which have very different damping properties, is typically non-classical damping system. This results in inapplicability of traditional response spectrum method for isolated buildings. A multidimensional response spectrum method based on complex mode superposition is herein introduced, which properly takes into account the non-classical damping feature in the structure and a new method is developed to estimate velocity spectra from the commonly used displacement or pseudo-acceleration spectra based on random vibration theory. The error of forced decoupling method, an approximated approach, is discussed in the viewpoint of energy transfer. From the base-isolated benchmark model, as a numerical example, application of the procedure is illustrated companying with comparison study of time-history method, forced decoupling method and the proposed method. The results show that the proposed method is valid, while forced decoupling approach can't reflect the characteristics of isolated buildings and may lead to insecurity of structures.

• Journal of Radiation Protection and Research
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• 제21권4호
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• pp.285-296
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• 1996

NaI(T1) 섬광검출기를 이용하여 감마선원인 Cr-51, Cs-137, Mn-54, Zn-65에 대하여 공기와 깊이가 다른 수중에서 에너지스펙트럼을 조사하였다. 측정한 스펙트럼의 차이와 변화를 정량적으로 비교분석하기 위해서 측정 스펙트럼을 곡선근사할 수 있는 응답함수를 구성하였다. 본 연구에서 밝혀진 바에 의하면 구성된 응답함수는 공기 중 뿐만 아니라 수중에서 측정된 스펙트럼을 거의 완전하게 나타낼 수 있었다. 또한 응답함수에 사용된 계수들을 비교함으로써 공기와 수중에서-물의 깊이에 따른-스펙트럼의 특성 면화를 정량적으로 규정할 수 있었다. 응답함수의 계수 가운데 전에너지 봉우리의 높이 및 비율이 물의 깊이에 가장 민감하게 영향을 받았으며, 그 외에도 전에너지 봉우리의 퍼진 정도, flat continuum의 높이, 1차 콤프턴산란 연속의 높이, Compton edge의 모양을 나타내는 응답함수계수 등에서 미약하나마 물의 깊이에 따라 변화를 보였다.

• 한국지진공학회논문집
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• 제27권6호
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• pp.245-252
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• 2023

In general, the design response spectrum in seismic design codes is based on the mean-plus-one-standard deviation response spectrum to secure high safety. In this study, response spectrum analysis was performed using seismic wave records adopted in domestic horizontal design spectrum development studies, while three response spectra were calculated by combining the mean and standard deviation of the spectra. Seismic wave spectral matching generated seismic wave sets matching each response spectrum. Then, seismic fragility was performed by setting three damage levels using a single-degree-of-freedom system. A correlation analysis was performed using a comparative analysis of the change in the response spectrum and the seismic fragility concerning the three response spectra. Finally, in the case of the response spectrum considering the mean and standard deviation, like the design response spectrum, the earthquake load was relatively high, indicating that conservative design or high safety can be secured.

• 한국지진공학회논문집
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• 제23권6호
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• pp.301-309
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• 2019

A methodology to assess seismic fragility of a nuclear power plant (NPP) using a conditional mean spectrum is proposed as an alternative to using a uniform hazard response spectrum. Rather than the single-scenario conditional mean spectrum, which is the conventional conditional mean spectrum based on a single scenario, a multi-scenario conditional mean spectrum is proposed for the case in which no single scenario is dominant. The multi-scenario conditional mean spectrum is defined as the weighted average of different conditional mean spectra, each one of which corresponds to an individual scenario. The weighting factors for scenarios are obtained from a deaggregation of seismic hazards. As a validation example, a seismic fragility assessment of an NPP containment structure is performed using a uniform hazard response spectrum and different single-scenario conditional mean spectra and multi-scenario conditional mean spectra. In the example, the number of scenarios primarily influences the median capacity of the evaluated structure. Meanwhile, the control frequency, a key parameter of a conditional mean spectrum, plays an important role in reducing logarithmic standard deviation of the corresponding fragility curves and corresponding high confidence of low probability of failure (HCLPF) capacity.

• 한국지진공학회논문집
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• 제20권1호
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• pp.55-62
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• 2016

It is important to select an accurate set of ground motions when conducting linear and nonlinear response history analyses of structures. This study proposes a method for selecting ground motions from a ground motion library with response spectra that match the target response spectrum mean, variance and correlation structures. This study also has addressed the determination of an appropriate value for the weight factor of a correlation structure. The proposed method is conceptually simple and straightforward, and does not involve a simulation algorithm. In this method, a desired number of ground motions are sequentially selected from first to last. The proposed method can be also used for selecting ground motions with response spectra that match the conditional spectrum. The accuracy and efficiency of the proposed procedure are verified with numerical examples.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.141-148
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• 2006

This study describes a generation of artificial earthquake wane compatible with seismic design spectrum. In seismic response analysis of building structures, the input ground accelerations have considerable effect on dynamic characteristics of structures. Therefore, it is important to properly select input ground motions for seismic response analysis. In this paper, the artificial earthquake wave are generated according to previously recorded earthquake waves in past earthquake events. The artificial wave have identical phase angles to the recorded earthquake wane, and their overall response spectra are compatible with seismic design spectrum with 5% of critical viscous damping. Each simulated earthquake wave has a identical phase angles to the original recorded ground acceleration, and match to design response spectra in the range of period from 0.02 to 10.0 seconds. It is concluded that the artificial earthquake waves simulated in this paper ate applicable as input ground motions for a seismic response analysis of building structures.

• Structural Engineering and Mechanics
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• 제51권4호
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• pp.581-599
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• 2014

In this paper the overall dynamic response of simple railway bridges subjected to high-speed trains is investigated numerically based on the mechanical models of simply supported single-span and continuous two-span Bernoulli-Euler beams. Each axle of the train, which is composed of rail cars and passenger cars, is considered as moving concentrated load. Distance, magnitude, and maximum speed of the moving loads are adjusted to real high-speed trains and to load models according to Eurocode 1. Non-dimensional characteristic parameters of the train-bridge interaction system are identified. These parameters permit a spectral representation of the dynamic peak response. Response spectra assist the practicing engineers in evaluating the expected dynamic peak response in the design process of railway bridges without performing time-consuming time history analyses.

• 한국방재학회 논문집
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• 제8권5호
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• pp.1-6
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• 2008

대부분의 내진설계기준에서는 설계지반운동을 정의하기 위해서 설계스펙트럼을 제시하고 있다. 기준에서 제시되는 설계스펙트럼은 일반적으로 5% 임계감쇠비에 대한 것이며, 이것은 일반적인 건축구조물에 적용할 수 있는 것이다. 에너지 소산장치나 면진 시스템의 적용이 점차 증가하고 있으며, 이러한 장치를 적용한 건축구조물의 내진해석을 위해서는 5% 임계감쇠비를 초과하는 설계스펙트럼이 필요하다. 5% 임계감쇠비에 대한 설계스펙트럼을 다른 임계감쇠비에 대한 설계스펙트럼으로 변환하기 위해서는 감쇠계수가 효과적으로 이용될 수 있다. 현재의 내진설계기준에서 제시하고 있는 감쇠계수는 강진자료를 바탕으로 제시된 것이다. 중진 및 약진은 강진과는 다른 특성을 가지므로, 이러한 감쇠계수가 중진 및 약진 지역에 적용하는 것은 충분한 검토가 필요할 것이다. 이 논문에서는 중진 및 약진자료를 이용한 감쇠계수를 제시하고, 현재 설계기준에서 제시하고 있는 감쇠계수와 비교하였다.

• 국제초고층학회논문집
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• 제9권3호
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• pp.273-282
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• 2020

An innovative high-rise timber-concrete hybrid structure was proposed in previous research, which is composed of the concrete frame-tube structure and the prefabricated timber modules as main structure and substructures, respectively. Considering that the timber substructures are built on the concrete floors at a different height, the floor response spectrum is more effective in estimating the seismic response of substructures. In this paper, the floor response spectra of the hybrid structure with different structural parameters were calculated using dynamic time-history analysis. Firstly, one simplified model that can well predict the seismic response of the hybrid structure was proposed and validated. Then the construction site, the mass ratio and the frequency ratio of the main-sub structure, and the damping ratio of the substructures were discussed. The results demonstrate that the peaks of the floor response spectra usually occur near the vibration periods of the whole structure, among which the first two peaks stand out; In most cases, the acceleration amplification effect on substructures tends to be more evident when the construction site is farther from the fault rupture; On the other hand, the acceleration response of substructures can be effectively reduced with an appropriate increase in the mass ratio of the main-sub structure and the damping ratio of the substructures; However, the frequency ratio of the main-sub structure has no discernible effect on the floor response spectra. This study investigates the characteristics of the floor response spectrum of the novel timber-concrete structure, which supports the future applications of such hybrid structure in high-rise buildings.