• 한국지반공학회논문집
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• 제33권12호
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• pp.45-58
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• 2017

최근 들어 시설물별 내진설계기준이 성능기반 내진설계로 전환됨에 따라, 신뢰성있는 비선형 응답이력해석(Response-history analysis, RHA)에 대한 요구가 높아지고 있다. 그러나, 부지응답해석 분야에 있어서는 1970년대 이후 등가선형 해석이 표준절차로 자리잡고 있음에 따라, 이를 대체하기 위해서는 비선형 응답이력해석의 신뢰성이 확보되어야 한다. 본 논문에서는 1989년 미국 Loma Prieta 지진기록을 바탕으로 다층지반에 대해서 비선형 RHA를 이용한 부지응답해석 결과의 신뢰성을 검증하였다. 이를 위하여, 비선형 RHA를 위한 비선형 지반모델의 선정방법과 3차원 해석시 요구되는 기반암 경계조건의 영향을 평가 하였다. 평가 결과, 제한된 조건하에서 가장 정확한 비선형 지반모델과 경계조건을 적용 시 비선형 RHA의 결과는 등가선형 해석결과와 유의미한 차이는 발생하지 않음을 알 수 있었다. 또한, 3차원 해석을 시행하는 경우, 전체 모델의 회전운동을 제어하기 위하여 최 하단부 흡수 경계조건을 적용해야 함을 알 수 있었다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.652-659
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• 2005

Even in moderate to low seismic regions like Korean peninsular where wind loading usually governs the structural design of a tall building, the probable structural impact of the design basis earthquake or the maximum credible earthquake on the selected structural system should be considered at least in finalizing the design. In this study, by using response spectrum analysis and linear time history analysis method, seismic performance evaluation was conducted for wind-designed concentrically braced steel highrise buildings. Both spectrum-compatible artificial accelerograms and recorded accelerograms were used as input ground motions for the time history analysis. The analysis results showed that wind-designed concentrically braced steel highrise buildings possess significantly increased elastic seismic capacity due to the system overstrength resulting from the wind-serviceability criterion and the width-to-thickness ratio limits on steel members. Time history analysis results generally tended to underestimate the seismic response as compared to those of response spectrum analysis.

• 한국지진공학회논문집
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• 제20권5호
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• pp.301-310
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• 2016

There are differences in seismic behavior between non-skewed bridges and skewed bridges due to in-plane rotations caused by pounding between the skewed deck and its abutments during strong earthquake. Many advances have been made in developing design codes and guidelines for dynamic analyses of non-skewed bridges. However, there remain significant uncertainties with regard to the structural response of skewed bridges caused by unusual seismic response characteristics. The purpose of this study is performing non-linear time history analysis of the bridges using abutment-soil interaction model considering pounding between the skewed deck and its abutments, and analyzing global seismic behavior characteristics of the skewed bridges to assess the possibility of unseating. Refined bridge model with abutment back fill, shear key and elastomeric bearing was developed using non-linear spring element. In order to evaluate the amplification of longitudinal and transverse displacement response, non-linear time history analysis was performed for single span bridges. Far-fault and near-fault ground motions were used as input ground motions. According to each parameter, seismic behavior of skewed bridges was evaluated.

• Tuberculosis and Respiratory Diseases
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• 제82권1호
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• pp.35-41
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• 2019

Background: Pulmonary tuberculosis can result in anatomical sequelae, and cause airflow limitation. However, there are no treatment guidelines for patients with a tuberculosis-destroyed lung. Recently, indacaterol effectiveness in chronic obstructive pulmonary disease (COPD) patients with Tuberculosis history (INFINITY) study revealed indacaterol provided bronchodilation and symptom improvement in COPD patients with a tuberculosis-destroyed lung. Methods: We conducted a post-hoc subgroup analysis of the randomized controlled trial, the INFINITY study, to determine factors associated with indacaterol response in a tuberculosis-destroyed lung with airflow limitation. Data from 68 patients treated with inhaled indacaterol, were extracted and analyzed. Factors associated with the response of forced expiratory volume in one second ($FEV_1$) to indacaterol treatment, were determined using linear regression analysis. Results: Of 62 patients included, 68% were male, and 52% had history of cigarette smoking. Patients revealed mean $FEV_1$ of 50.5% of predicted value with mean improvement of 81.3 mL in $FEV_1$ after indacaterol treatment for 8 weeks. Linear regression analysis revealed factors associated with response of $FEV_1$ to indacaterol included a short duration of smoking history, and high short-acting bronchodilator response. When patients with history of smoking were excluded, factors associated with response of $FEV_1$ to indacaterol included high short-acting bronchodilator response, and poor health-related quality of life score as measured by St. George's Respiratory Questionnaire for COPD. Conclusion: In a tuberculosis-destroyed lung with airflow limitation, short-acting bronchodilator response and smoking history can play a critical role in predicting outcomes of indacaterol treatment.

• Earthquakes and Structures
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• 제18권2호
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• pp.263-273
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• 2020

The use of energy concepts in seismic analysis and design of structures requires the understanding of the input energy response of multi-degree-of-freedom (MDOF) systems subjected to strong ground motions. For design purposes and non-time consuming analysis, however, it would be beneficial to associate the input energy response of MDOF systems with those of single-degree-of-freedom (SDOF) systems. In this paper, the theoretical formulation of energy input to MDOF systems is developed on the basis that only a particular portion of the total mass distributed among floor levels is effective in the nth-mode response. The input energy response histories of several reinforced concrete frames subjected to a set of eleven horizontal acceleration histories selected from actual recorded events and scaled in time domain are obtained. The contribution of the fundamental mode to the total input energy response of MDOF frames is demonstrated both graphically and numerically. The input energy of the fundamental mode is found to be a good indicator of the total energy input to two-dimensional regular MDOF structures. The numerical results computed by the proposed formulation are verified with relative input energy time histories directly computed from linear time history analysis. Finally, the elastic input energies are compared with those computed from time history analysis of nonlinear MDOF systems.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2696-2707
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• 2021

The purpose of this study is to investigate the efficiency of various structural modeling schemes for evaluating seismic performances and fragility of the reactor containment building (RCB) structure in the advanced power reactor 1400 (APR1400) nuclear power plant (NPP). Four structural modeling schemes, i.e. lumped-mass stick model (LMSM), solid-based finite element model (Solid FEM), multi-layer shell model (MLSM), and beam-truss model (BTM), are developed to simulate the seismic behaviors of the containment structure. A full three-dimensional finite element model (full 3D FEM) is additionally constructed to verify the previous numerical models. A set of input ground motions with response spectra matching to the US NRC 1.60 design spectrum is generated to perform linear and nonlinear time-history analyses. Floor response spectra (FRS) and floor displacements are obtained at the different elevations of the structure since they are critical outputs for evaluating the seismic vulnerability of RCB and secondary components. The results show that the difference in seismic responses between linear and nonlinear analyses gets larger as an earthquake intensity increases. It is observed that the linear analysis underestimates floor displacements while it overestimates floor accelerations. Moreover, a systematic assessment of the capability and efficiency of each structural model is presented thoroughly. MLSM can be an alternative approach to a full 3D FEM, which is complicated in modeling and extremely time-consuming in dynamic analyses. Specifically, BTM is recommended as the optimal model for evaluating the nonlinear seismic performance of NPP structures. Thereafter, linear and nonlinear BTM are employed in a series of time-history analyses to develop fragility curves of RCB for different damage states. It is shown that the linear analysis underestimates the probability of damage of RCB at a given earthquake intensity when compared to the nonlinear analysis. The nonlinear analysis approach is highly suggested for assessing the vulnerability of NPP structures.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2007년 가을학술발표회
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• pp.317-333
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• 2007

The Round-Robin Test (RRT) for ground response analysis was performed by Division of Geotechnical Earthquake Engineering of Korean Geotechnical Society. This research analyzed the influence of analysis methods on variation of ground response by using the results of this RRT. The analysis methods include equivalent linear analysis, non-linear analysis and effective stress analysis. A total of 5 teams among 12 teams applied two kinds of analysis methods. This research compared the results of these 5 teams and analyzed the variation of the results according to analysis methods. The compared results were shear stress-shear strain relation, transfer function, time history and the response spectrum of ground surface acceleration, peak ground acceleration, peak shear strain and maximum excess pore pressure ratio.

• Computers and Concrete
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• 제11권1호
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• pp.51-61
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• 2013

This paper describes earthquake response of the Arhavi Highway Tunnel its geometrical properties, 3D finite element model and the linear time history analyses under a huge ground motion considering soil-structure interaction. The Arhavi Highway Tunnel is one of the tallest tunnels constructed in the Black Sea region of Turkey as part of the Coast Road Project. The tunnel has two tubes and each of them is about 1000 m tall. In the study, lineartime history analyses of the tunnel are performed applying north-south, east-west and up accelerations components of 1992 Erzincan, Turkey ground motion. In the time history analyses, Rayleigh damping coefficients are calculated using main natural frequency obtained from modal analysis. Element matrices are computed using the Gauss numerical integration technique. The Newmark method is used in the solution of the equation of motion. Because of needed too much memory for the analyses, the first 10 second of the ground motions, which is the most effective duration, is taken into account in calculations. The results obtained 3D finite element model are presented. In addition, the displacement and stress results are observed to be allowable level of the concrete material during the earthquakes.

• Earthquakes and Structures
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• 제20권4호
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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.

• Earthquakes and Structures
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• 제6권4호
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• pp.375-392
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• 2014

Time history analyses have been preferred commonly in earthquake engineering area to determine earthquake performances of structures in recent years. Advances in computer technology and structural analysis have led to common usage of time history analyses. Eurocode 8 allows the use of real earthquake records as an input for linear and nonlinear time history analyses of structures. However, real earthquake records with the desired characteristics sometimes may not be found, for example depending on soil classes, in this case artificial and synthetic earthquake records can be used for seismic analyses rather than real records. Selected earthquake records should be scaled to a code design spectrum to reduce record to record variability in structural responses of considered structures. So, scaling of earthquake records is one of the most important procedures of time history analyses. In this paper, four real earthquake records are scaled to Eurocode 8 design spectrums by using SESCAP (Selection and Scaling Program) based on time domain scaling method and developed by using MATLAB, GUI software, and then scaled and real earthquake records are used for linear time history analyses of a six-storied building. This building is modeled as spatial by SAP2000 software. The objectives of this study are to put basic procedures and criteria of selecting and scaling earthquake records in a nutshell, and to compare the effects of scaled earthquake records on structural response with the effects of real earthquake records on structural response in terms of record to record variability of structural response. Seismic analysis results of building show that record to record variability of structural response caused by scaled earthquake records are fewer than ones caused by real earthquake records.