• Earthquakes and Structures
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• 제22권3호
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• pp.219-230
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• 2022

Knowing that the variability of soil properties is an important source of uncertainty in geotechnical analyses, we will study in this paper the effect of this variability on the seismic response of a structure within the framework of Soil Structure Interaction (SSI). We use the proposed and developed model (N2-ISS, Mekki et al., 2014). This approach is based on an extension of the N2 method by determining the capacity curve of the fixed base system oscillating mainly in the first mode, then modified to obtain the capacity curve of the system on a flexible basis using the concept of the equivalent nonlinear oscillator. The properties of the soil that we are interested in this paper will be the shear wave velocity and the soil damping. These parameters will be modeled at first, as independent random fields, then, the two parameters will be correlated. The results obtained showed the importance of the use of random field in the study of SSI systems. The variability of soil damping and shear wave velocity introduces significant uncertainty not only in the evaluation of the damping of the soil-structure system but also in the estimation of the displacement of the structure and the base-shear force.

• Steel and Composite Structures
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• 제47권3호
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• pp.339-353
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• 2023

The primary objective of the current study is to optimize and evaluate the seismic performance of steel momentresisting frame (MRF) structures considering soil-structure interaction (SSI) effects. The structural optimization is implemented in the context of performance-based design in accordance with FEMA-350 at different confidence levels from 50% to 90% by taking into account fixed- and flexible-base conditions using an efficient metaheuristic algorithm. Nonlinear response-history analysis (NRHA) is conducted to evaluate the seismic response of structures, and the beam-on-nonlinear Winkler foundation (BNWF) model is used to simulate the soil-foundation interaction under the MRFs. The seismic performance of optimally designed fixed- and flexible-base steel MRFs are compared in terms of overall damage index, seismic collapse safety, and interstory drift ratios at different performance levels. Two illustrative examples of 6- and 12-story steel MRFs are presented. The results show that the consideration of SSI in the optimization process of 6- and 12-story steel MRFs results in an increase of 1.0 to 9.0 % and 0.5 to 5.0 % in structural weight and a slight decrease in structural seismic safety at different confidence levels.

• Earthquakes and Structures
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• 제26권6호
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• pp.463-475
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• 2024

The study aims to investigate the pounding that occurs between the isolator's ring and slider of isolated structures resulting from excessive seismic excitation, while considering soil-structure interaction. The dynamic responses and poundings of structures subjected a series seismic records were comparatively analyzed for three different soil types and fixed-base structures. A series of parametric studies were conducted to thoroughly discuss the effects of the impact displacement ratio, the FPB friction coefficient ratio, and the radius ratio on the structural dynamic response when considering impact and SSI. It was found that the pounding is extremely brief, with an exceptionally large pounding force generated by impact, resulting in significant acceleration pulse. The acceleration and inter-story shear force of the structure experiencing pounding were greater than those without considering pounding. Sudden changes in the inter-story shear force between the first and second floors of the structure were also observed. The dynamic response of structures in soft ground was significantly lower than that of structures in other ground conditions under the same conditions, regardless of the earthquake wave exciting the structure. When the structure is influenced by pulse-type earthquake records, its dynamic response exhibits a trend of first intensifying and then weakening as the equivalent radius ratio and friction coefficient ratio increase. However, it increases with an increase in the pounding displacement ratio, equivalent radius ratio, friction coefficient ratio, and displacement ratio when the structures are subjected to non-pulse-type seismic record.

• Earthquakes and Structures
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• 제12권2호
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• pp.165-175
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• 2017

This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full probabilistic analysis methods like MC commonly are very time consuming, the feasibility of simple approximate methods' application including First Order Second Moment (FOSM) method and ASCE41 proposed approach for the soil uncertainty considerations is investigated. By comparing the results of the approximate methods with the results obtained from MC, it's observed that the results of both FOSM and ASCE41 methods are in good agreement with the results of MC simulation technique and they show acceptable accuracy in predicting the response variability.

• 한국인구학
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• 제10권2호
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• pp.58-81
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• 1987

본 연구의 목적은 미국에 거주하는 65세 이상의 한국 영주권자 노인들의 주거형태에 영향을 끼치는 요인들을 조사하는 것이다. 이를 위해 1990년 미국 센서스 데이터인 Public Use Microdata(Samples PUMS)의 8% sub-sample을 이용하였다. 주거형태에 영향을 주는 주요변인들로 동화과정(이민 온 연령과 영어구사능력), 경제적 요인 (지난 일년간의 개인수입과 보조적 보장소득 수혜여부), 건강상태(외출활동과 일상생활 활동능력), 그리고 민족 지역공동체 등이 포함되었으며, 나이, 성별, 교육, 결혼상태 등의 변인들을 함께 통제하여 분석하였다. 연구결과 동화과정과 경제적 여유는 재미 한국 영주권자 노인의 단독주거에 긍정적인 역할을 하고 있는 반면, 건강과 한국 지역공동체는 주거형태에 통계적으로 일관된 영향력을 보이지 않았다. 동화과정의 측정변수로서 이민연령의 효과는 배우자 유무에 상관없이 통계적으로 유의미하게 한국 노인들의 단독거주에 긍정적인 것으로 나타난 반면, 영어구사 능력의 경우, 무배우자 노인들 중 영어구사능력이 높을수록 가족과 함께 살고 있었고, 유배우자 노인들에게는 영어를 구사할 수 있는 능력이 가족과 떨어져 사는 데 긍정적인 역할을 하였다. 특히 무배우자 노인들의 경우, 이민연령의 효과 역시 순수한 의미의 동화과정이라기보다는 사회보장 프로그램을 수혜하기 위한 자격조건과 한인지역 네트워트 파악을 위한 적응기간이라는 설명이 더 설득력이 있다. 배우자의 유무와는 무관하게 보조적 보장소득의 혜택을 받고 있는 한국 노인들이 그렇지 않은 노인들보다 두 세배 이상 단독주거를 하고 있었다. 일단 보조적 보장소득을 수혜하고 있는 노인들에게는 메디케이드, 푸드스탬프, 정부지원 월세보조금, 공공요금 할인 등 다양한 사회보장 프로그램을 받을 수 있는 자격이 주어지므로 대부분의 보조적 보장소득 수혜 노인들은 단순히 금전적인 수입의 측면뿐 아니라 그 외의 사회보장 프로그램에 의존하고 있다. 이러한 면에서 보조적 보장소득의 수혜는 한국 영주권자 노인들의 독립적인 삶에 큰 역할을 하고 있다. 이러한 사회복지 프로그램을 영주권자들에게는 전면 금지하는 새로운 사회복지법은 재미 한국 영주권자 노인들뿐 아니라 그들의 가족들에게도 막대한 경제적 부담을 줄 것이다. 본 논문은 영주권자 노인들을 대상으로 분석한 것이지만, 주거형태를 비롯한 일반적인 특성을 비교해 보면 영주권자, 귀화 시민권자, 그리고 미국태생 노인들은 다른 성격의 집단들임을 보여주고 있다. 종래의 소수민족 노인들에 관한 연구들이 이민자 노인들을 영주권자와 귀화 시민권자의 구분없이 하나의 집단으로 간주하고 분석해 왔던 것을 볼 때, 앞으로의 연구는 이론적으로나 방법론적으로 시민권의 유무가 주거형태에 끼치는 영향도 함께 고려해야 할 것이다.

• 한국인구학
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• 제20권2호
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• pp.99-134
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• 1997

본 연구의 목적은 미국에 거주하는 65세 이상의 한국 영주권자 노인들의 주거형태에 영향을 끼치는 요인들을 조사하는 것이다. 이를 위해 1990년 미국 센서스 데이터인 Public Use Microdata(Samples PUMS)의 8% sub-sample을 이용하였다. 주거형태에 영향을 주는 주요변인들로 동화과정(이민 온 연령과 영어구사능력), 경제적 요인 (지난 일년간의 개인수입과 보조적 보장소득 수혜여부), 건강상태(외출활동과 일상생활 활동능력), 그리고 민족 지역공동체 등이 포함되었으며, 나이, 성별, 교육, 결혼상태 등의 변인들을 함께 통제하여 분석하였다. 연구결과 동화과정과 경제적 여유는 재미 한국 영주권자 노인의 단독주거에 긍정적인 역할을 하고 있는 반면, 건강과 한국 지역공동체는 주거형태에 통계적으로 일관된 영향력을 보이지 않았다. 동화과정의 측정변수로서 이민연령의 효과는 배우자 유무에 상관없이 통계적으로 유의미하게 한국 노인들의 단독거주에 긍정적인 것으로 나타난 반면, 영어구사 능력의 경우, 무배우자 노인들 중 영어구사능력이 높을수록 가족과 함께 살고 있었고, 유배우자 노인들에게는 영어를 구사할 수 있는 능력이 가족과 떨어져 사는 데 긍정적인 역할을 하였다. 특히 무배우자 노인들의 경우, 이민연령의 효과 역시 순수한 의미의 동화과정이라기보다는 사회보장 프로그램을 수혜하기 위한 자격조건과 한인지역 네트워트 파악을 위한 적응기간이라는 설명이 더 설득력이 있다. 배우자의 유무와는 무관하게 보조적 보장소득의 혜택을 받고 있는 한국 노인들이 그렇지 않은 노인들보다 두 세배 이상 단독주거를 하고 있었다. 일단 보조적 보장소득을 수혜하고 있는 노인들에게는 메디케이드, 푸드스탬프, 정부지원 월세보조금, 공공요금 할인 등 다양한 사회보장 프로그램을 받을 수 있는 자격이 주어지므로 대부분의 보조적 보장소득 수혜 노인들은 단순히 금전적인 수입의 측면뿐 아니라 그 외의 사회보장 프로그램에 의존하고 있다. 이러한 면에서 보조적 보장소득의 수혜는 한국 영주권자 노인들의 독립적인 삶에 큰 역할을 하고 있다. 이러한 사회복지 프로그램을 영주권자들에게는 전면 금지하는 새로운 사회복지법은 재미 한국 영주권자 노인들뿐 아니라 그들의 가족들에게도 막대한 경제적 부담을 줄 것이다. 본 논문은 영주권자 노인들을 대상으로 분석한 것이지만, 주거형태를 비롯한 일반적인 특성을 비교해 보면 영주권자, 귀화 시민권자, 그리고 미국태생 노인들은 다른 성격의 집단들임을 보여주고 있다. 종래의 소수민족 노인들에 관한 연구들이 이민자 노인들을 영주권자와 귀화 시민권자의 구분없이 하나의 집단으로 간주하고 분석해 왔던 것을 볼 때, 앞으로의 연구는 이론적으로나 방법론적으로 시민권의 유무가 주거형태에 끼치는 영향도 함께 고려해야 할 것이다.

• Earthquakes and Structures
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• 제7권1호
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• pp.83-99
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• 2014

This study is devoted to estimate higher-mode effects for multi-story structures with considering soil-structure interaction subjected to decomposed parts of near-fault ground motions. The soil beneath the super-structure is simulated based on the Cone model concept. Two-dimensional structural models of 5, 15, and 25-story shear buildings are idealized by using nonlinear stick models. The ratio of base shears for the soil-MDOF structure system to those obtained from the equivalent soil-SDOF structure system is selected as an estimator to quantify the higher-mode effects. The results demonstrate that the trend of higher-mode effects is regular for pulse component and has a descending variation with respect to the pulse period, whereas an erratic pattern is obtained for high-frequency component. Moreover, the effect of pulse component on higher modes is more significant than high-frequency part for very short-period pulses and as the pulse period increases this phenomenon becomes vice-versa. SSI mechanism increases the higher-mode effects for both pulse and high-frequency components and slenderizing the super-structure amplifies such effects. Furthermore, for low story ductility ranges, increasing nonlinearity level leads to intensify the higher-mode effects; however, for high story ductility, such effects mitigates.

• 가정과삶의질연구
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• 제26권6호
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• pp.123-134
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• 2008

This study aimed to assess the roll of various abusive factors on suicide thoughts. In particular, the effects of negligence, physical and emotional abuse, as the subordinate variables of abuse, were examined on suicide ideation. In addition, the mediation effects of shame-proneness and friendships were also investigated. To achieve these specific objectives, subordinate dimensions of abuse such as negligence, physical abuse and emotional abuse were measured for 277 male and 275 female students from Seoul middle schools using a measurement tool. Specifically, experiences of being abused and neglected, the level of suicide thoughts using scale for suicidal ideation (SSI), the level of shame-proneness and friendships using personal feelings questionnaire-2(PFQ-2), and schoolmate relationships were measured using a questionnaire. Analysis of collected data revealed that while suicide thoughts showed significant positive relationship with abuse and shame-proneness, there was a significant negative relationship between suicide thoughts and friendships. In particular, negligence, physical abuse and emotional abuse had significant effects on suicide ideation, while emotional abuse had the greatest effect on suicide ideation. Shame-proneness and friendships partially mediated abuse and suicide thoughts. The findings of this study have contributed to understanding of factors related to suicide thoughts. In particular, the mediation effects of shame-proneness and friendships have been highlighted.

• Smart Structures and Systems
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• 제10권4_5호
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• pp.393-410
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• 2012

The 610 m high Canton Tower (formerly named Guangzhou New Television Tower) is currently considered as a benchmark problem for structural health monitoring (SHM) of high-rise slender structures. In the benchmark study task I, a set of 24-hour ambient vibration measurement data has been available for the output-only system identification study. In this paper, the vector autoregressive models (ARV) method is adopted in the operational modal analysis (OMA) for this TV tower. The identified natural frequencies, damping ratios and mode shapes are presented and compared with the available results from some other research groups which used different methods, e.g., the data-driven stochastic subspace identification (SSI-DATA) method, the enhanced frequency domain decomposition (EFDD) algorithm, and an improved modal identification method based on NExT-ERA technique. Furthermore, the environmental effects on the estimated modal parameters are also discussed.

• Earthquakes and Structures
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• 제24권3호
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• pp.165-181
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• 2023

The effectiveness of fluid viscous dampers (FVDs) on dynamic response mitigation of coupled two adjacent structures was investigated, considering soil-structure interaction (SSI) effects under earthquake excitation. A numerical procedure was employed to evaluate system response. The finite elements were used for the numerical treatment of the adjacent buildings and soil region. Viscous boundary conditions were used as special non-reflecting boundaries on the edges of finite soil region. According to the results, the FVDs were found to be very effective for dynamic response mitigation of the adjacent buildings, even if considering the soil medium. The results showed that the most affecting parameter on the system response was found to be soil type. It was also concluded that when adjacent structures coupled by FVDs, the maximum values of the roof displacements, the base shear forces, and the base bending moments could decrease up to around 50%. Changing in lateral stiffness of the one building has minor effects on the effectiveness of viscous dampers.