Earticle

본연구의 목적은 깊은보-외부기둥 접합부에 대한 반복횡하중실험과 비선형 유한요소해석 겨로가를 비교함으로써 깊은보-외부기둥접합부의 비선형 거동을 예측할 수있는 해석법을 제시하는데 있다. 깊은보-외부기둥접합부의 거동특성과 성능을 평가하기 위해 반복횡하중 실험은 수행되었으며, 실험에 적용된 변수는 횡방향철근량(ACI기준, Sheikh제안식)이다. 비선형 해석에는 RCAHEST 프로그램을 사용하였다. 해석결과와 실험결과를 비교함으로써 해석법을 검증하였다. 해석결과는 깊은보-외부기둥접합부의 비선형 지진거동수준까지 실험결과와 거의 일치하는 결과를 보여주었다.

The object of this study was to present the nonlinear finite analysis procedure to simulate the seismic behavior of deep beam-and-exterior column joints through comparing cyclic loading tests results and nonlinear finite element analysis. Reversed cyclic loading tests were conducted to estimate the performance and behavioral characteristics of deep beam-and-exterior column joints. Experimental parameter was the amounts of transverse reinforcements (designed by ACI code and Sheikh's procedure). Nonlinear analysis of specimen was done using RCAHEST. Analytical procedures were verified by comparing analytical results with the experimental ones. It was evident that the analytical results closely correspond with experimental ones in the inelastic seismic behavior of deep beam-and-exterior column joint.

Predicting seismic response to earthquake load which can happen during the span of the building and evaluating seismic performance are very critical research tasks in the context of earthquake engineering with respect to performance-based seismic design. The main objective of performance-assessment is to evaluate the behavior of a system at different seismic hazard levels. To predict structure response to earthquake load which can arise, it is necessary to understand nonlinear behaviors characteristics. Ideally, the nonlinear response history analysis should faithfully simulate all significant modes of deformation and deterioration in the structure from the onset of damage up to collapse. We can obtain nonlinear response through three hysteretic parameters such as strength degradation, stiffness degradation and pinching behavior respectively. In this study, it is to compare inelastic behaviors of reinforced concrete upper wall-lower frame structures and to suggest more reliable hysteretic models with simple bilinear model for nonlinear analysis of structure. From a limited sensitivity study, it is founded that strength degradation and pinching behavior have more effect rather than stiffness degradation on the top story response.

우리나라 지역의 인구감소는 그간 활발히 논의되어 왔으나, 최근 들어 심각한 수준의 저출산·고령화로 인해 이제는 ‘지방소멸’이라는 단어까지 사용되고 있다. 지방소멸은 도시를 넘어 국가적인 차원의 문제가 되고 있으며, 국토의 효율적 이용을 저해하는 심각한 문제가 되고 있다. 행정안전부는 지방소멸 대응을 위해 인구감소지수를 산출하였으며, 이를 바탕으로 인구감소지역을 지정하고 지원 정책을 운영 중에 있다. 그러나 이러한 대응에도 불구하고, 인구감소지수를 활용한 실증연구는 부족한 실정이다. 본 연구는 인구감소지수를 활용해 인구감소에 영향을 미치는 요인들을 분석하여 정책적 시사점을 제시하는 것을 목적으로 한다. 이를 위해 본 연구는 지역 매력도 개념을 활용하여 인구감소지수에 영향을 미치는 지역 특성들을 살펴보았다. 분석 방법으로는 머신러닝 기법인 랜덤 포레스트를 활용하였다. 분석결과, 지역 매력도 요인 중 GRDP, 노후주택 비율, 의료 인프라가 인구감소지수에 가장 큰 영향을 미치는 핵심 변수로 식별되었다. 이들 변수는 인구감소지수와 비선형적 관계를 보였으며, 사회경제적 여건이 취약할수록 해당 요인 확충에 따른 인구감소지수 개선의 효과가 크게 나타나는 한계효과 체감 양상이 확인되었다. 따라서 지방소멸 대응을 위해 모든 분야에 대한 일률적인 자원 배분보다는 지역별 사회경제적 여건을 토대로 최적의 효율을 보일 수 있는 자원 투입 목표를 도출하여 정책 집행의 적정 기준으로 삼는 것이 필요할 것이다.

Population decline, intensified by low birth rates and aging, has recently led to the emergence of the term “local extinction,” particularly due to population outflows from non-metropolitan to metropolitan areas. Local extinction refers to a critical loss of population that threatens the sustainability of basic services in a region. In response, the Ministry of the Interior and Safety in South Korea developed a Depopulation Index to identify at-risk areas and implement supportive policies. However, empirical research utilizing this index remains limited. This study explores the predictive factors for population decline using the concept of regional attractiveness and the Depopulation Index. Key variables such as employment, cultural amenities, and public services were examined using the Random Forest machine learning algorithm. Results indicate that all variables exhibit meaningful predictive power within the model, particularly showing more pronounced variations in regions with poor infrastructure. The findings emphasize the importance of targeting vulnerable infrastructure in depopulated areas and setting clear policy criteria. While this research contributes to policy refinement by applying an official government index, it also acknowledges inherent limitations, specifically the empirical constraints in perfectly replicating the official index due to data restrictions.

A number of piloti buildings were used as a multi-family housing because of their relative low cost maintenance and availability of enough parking spaces. However, this type of structures were somewhat severely damaged due to recent earthquakes in Korea. In general, piloti structure shows a relatively weak story in the first story compare to the rahmen structure due to the soft story irregularity. As a result, non-elastic deformation of structural members of the weak story can occur intensively, and then resulting in a sudden change in the seismic load flow which can lead to the member's brittle failure. Moreover, the damage of the piloti structure can be differed from many factors such as the location of the core surrounded by the wall. In this study, a nonlinear time history analysis was used to analyze how the piloti structure responds according to the core location and how the damage changes when the piloti structure deterioration. Test results show that the eccentricity of the Piloti structure increased, the natural period of structure was increased. In addition, as the eccentricity increased, the damage of the vertical members were increased in the weak story.

RCS construction method is to take an advantage by applying reinforced concrete column and steel beam. RCS construction method has a complex structural analysis, compared with single structural system, due to interaction of different material, behavior of load distribution, diversity of joint detail and failure behavior. Therefore, this study aims to describe behavior of RCS joint as a simplified analysis model. The first, for understand behavior of RCS joint through test literatures related to RCS from the inside and outside of country and presented an analysis model, which to reflect each characteristic. So first of all, the researcher divided RCS specimen into four groups, according to its form and stress distribution element. The 'C' group, which is a flexural failure model, was explained properly using a factor in not order to generate stiffness reduction, strength reduction and pinching with polygonal model. The 'A', 'B' and 'D' groups, which are origin oriented models, were explained properly using smooth model and they had little bigger values in stiffness and strength reduction than general RC joint and a factor of pinching was explained through a combination among slip length, slip sharpness and moment level of slip in each group.

A recent large-space structure is frequently made by light-weight structural system and it has a good mechanical efficiency. To make the light-weight structural system we are using tension members mainly. Since cable dome structures which are a soft structures are very flexible, stresses and nodal coordinates of the other members are changed when we control the stress of one member. Therefore we have to do two kind of works for effective and accurate construction of the cable dome structures. The first work is to make a working scenario to complete the final objective form, and the second is to revise constructional errors occurred in process of actual works. These works are called constructional analysis. In this study, we try to approach the constructional analysis of the cable dome structures using the numerical method, and then verify it.

Nonlinear analysis of reinforced concrete (RC) structures is performed by using isogeometric Reissner-Mindlin (RM) shell element. The elasto-plastic constitutive model is employed to express the nonlinear behavior of concrete material and the equivalent smeared steel layer is introduced to represent steel reinforcement. The arc-length control method is used to produce the entire load-displacement path of RC structures. Finally, three benchmark tests are carried out to verify the performance of the present shell element. From isogeometric analysis, the present results show a good agreement with experimental results and it is provided as future benchmark test solutions.

Nonlinear analysis of reinforced concrete structures is carried out by using Reissner-Mindlin (RM) shell finite element (FE). The brittle inelastic characteristic of concrete material is represented by using the elasto-plastic fracture (EPF) material model with the relevant material models such as cracking criteria, shear transfer model and tension stiffening model. In particular, assumed strains are introduced in the formulation of the present shell FE in order to avoid element deficiencies inherited in the standard RM shell FE. The arc-length control method is used to trace the full load-displacement path of reinforced concrete structures. Finally, four benchmark tests are carried out and numerical results are provided as future reference solutions produced by RM shell element with assumed strains.

A finite element analysis technology applicable to the prediction of the static nonlinear response of cable roof structure is presented. The unified kinematic description is employed to formulate the present cable element and different strain definitions such as Green-Lagrange strain, Biot strain and Hencky strain can be adopted. The Newton-Raphson method is used to trace the nonlinear load-displacement path. In the iteration process, the compressive stress of a cable element is not allowed. For the verification of the present cable element, four numerical examples are tackled. Finally, numerical results obtained by using the present cable element are provided as new benchmark test results for cable structures under static loads.

Liquid sloshing displays the highly nonlinear free surface fluctuation when either the external excitation is of large amplitude or its frequency approaches natural sloshing frequencies. Naturally, the accurate tracking of time-varying free surface configuration becomes a key task for the reliable prediction of the sloshing time-history response. However, the numerical instability and dissipation may occur in the nonlinear sloshing analysis, particularly in the long-time beating simulation, when two simulation parameters, the relative time-increment parameter a and the fluid mesh pattern, are not elaborately chosen. This paper intends to examine the effects of these two parameters on the potential-based nonlinear finite element method introduced for the large amplitude sloshing flow.

Earthquakes present significant challenges to buildings contemporary, and the response of RC frame structures to seismic activity is influ-enced by various characteristics, including column section designs and orientation. The specific designs of column sections directly impact the lateral stiffness of the entire structure. Considering the weak story in an RC frame structure and making changes to column orientations can lead to structural issues in both vertical and lateral stiffness, resulting in weaknesses in the structural plan that increase vulnerability to seismic forces. Therefore, the most crucial aspect of seismic design is creating an efficient structural system that satisfies all seismic per-formance objectives, including considerations for IO (immediate occupancy), LS (life safety), and CP (collapse prevention) under plastic hinge analysis. In evaluating the seismic performance of buildings, nonlinear static pushover analysis has become increasingly prevalent over the past decades. This research concludes that columns with different orientations and stories exhibit different performance attributes when subjected to nonlinear static analysis using both SAP 2000 and ABAQUS. Regarding the structural influences due to different stories, this research summarizes variations in structural performance observed across columns with various orientations and heights, ranging from the first floor to the fifth floor. These findings are expected to provide valuable insights for future analyses examining the performance of column orientations as well as serve as a valuable reference for new construction of RC structures or reinforcement of existing RC structures against seismic activities.

본 연구에서는 원형 박판 구조물의 안정성에 대하여 해석 하였다. 임계하중은 하중을 점차적으로 증가하여 구조물이 파괴가 발생하여 안정성을 상실 하는 상태에서 가장 작은 하중을 의미한다. 판구조의 안정성을 임계하중의 크기로 기초를 두고 해석 하였다. 원형 박판구조의 차분해석은 일반 판구조와 같으므로 최근에 많은 연구의 대상이 되어왔다. 차분법은 복잡한 구조물에서도 물론, 다양한 경계조건을 포함하는 문제에 이르기까지 효과적인 수치방법이다. 본 연구에서는 기본 박판구조의 지배방정식을 유도하고 차분화 하여 직접적으로 접근하였다. 원 둘레 의 지점이 힌지 받침으로, 등분포 하중을 받고 있는 박판을 기하학적 비선형 해석으로 수행하여 원형 박판의 처짐 및 응력을 해석 하였다.

본 연구는 고등학교 학생 중 학교 부적응자 결정요인을 개인수준의 주관적 자료가 아닌 학교 수준의객관적 자료에 근거하여 분석하는데 목적이 있다. 기존 연구들을 포괄할 수 있는 변수로서 학교, 교육, 교사, 학생, 부모 및 가정 요인들이 학교 부적응에 미치는 영향을 검증하였다. 검증결과 첫째, 지역적으로 학교가 대도시에 비해 중소 도시, 읍면지역에 위치할수록, 학교의 규모가 커질수록 부적응자수가 많아지고, 학교의 재정이 안정적일수록 부적응자는 줄어들었다. 둘째, 교육프로그램으로서 방과후 교과 프로그램 비율이 높아질 때 부적응자가 감소하였으며, 셋째, 교사에서는 성과급의차등지급이 증가할수록, 전문성 있는 교사의 비율이 높아질수록 부적응자가 감소하였다. 넷째, 학생요소에서는 기초학력 미달 학생들의 비율이 높아질수록 부적응자수가 많아지는 것으로 나타났으며, 관계적인 측면에서 동아리 활동이 많아질수록 부적적응자수가 감소하였다. 마지막으로 부모 및 가정 요소에서 경제적인 측면을 나타내는 급식학생 비율, 보호자 지원비율이 높을수록 부적응자 수가감소하고 있다.

This paper examines possible causal relationships of high school dropouts in the lights of 5 major categories: school, educational program, teachers and staff, students, parents and their families. Since the number of high school dropouts – a count variable – is a dependent variable in our model, the Poisson regression model with three-year panel data from 2011 to 2013 is used. Empirical findings are as follows; (1) high school dropouts are more likely to be from small or middle cities than big cities while a school’s size is positively associated with the number of dropouts, (2) after-school programs help students stay in school, (3) incentive for teachers seems to be working positively, (4) academic performance of each student is one of the main determinants for dropping out, and (5) family’s financial stability also plays a significant role in reducing dropouts.

최근에 카오스 이론을 사회과학의 한 분야의 사랑 모델에 적용하고자 하는 노력을 지속하고 있다. 로미오와 줄리엣으로 표현하는 미분 방정식에서 카오스 거동을 만들기 위해서 외력을 인가한다. 그러나 이 외력은 사람의 감정을 정확하게 표현하지 못하는 단점을 가진다. 본 논문에서는 이러한 단점을 해결하기 위하여, 로미오와 줄리엣의 사랑모델에서 외력을 사람의 말이나 행동에 가장 유사한 형태로 제공하기 위해 퍼지 소속 함수를 도입하고 이를 삼각 퍼지 소속 함수를 제시하였다. 또한 제시된 퍼지 소속 함수를 가진 로미오와 줄리엣의 사랑모델에서 카오스 거동을 확인하기 위하여, 시계열과 위상공간을 이용하였으며 이를 통하여 카오스 거동의 존재를 확인한다.

Recently, we have been continued effort that chaotic theory apply into love model which is an area of social science. To make the chaotic behaviors in the differential equation that represent as Romeo and Juliet, we apply an external force to the differential equation. However, this external force have disadvantage that cannot exactly represent for emotion of human. In this paper, to solve these advantage, we introduce triangular fuzzy membership function to provide the external force that can describe most similar status for action and word of human in the love model of Romeo and Juliet. Also, to confirm the chaotic behaviors in the love model of Romeo and Juliet with proposed fuzzy membership function, we use time series and phase plane.

본 논문에서는 앵커로 연결된 콘크리트-강재 구조물이 극한 반복주기하중을 받는 경우를 수치 시뮬레이션하기 위하여 필요한 콘크리트-앵커 부착모형에 대하여 논하였다. 제안되는 앵커의 부착-미끄러짐 수치모형은 비선형 일축 연결요소의 조합으로 이루어지며 인발실험 결과를 이용하여 부착-미끄러짐 모형의 인자를 결정할 수 있다. 제안된 앵커 부착-미끄러짐 모형을 Abaqus 요소의 조합으로 구성하고, 이를 사용한 해석 결과와 앵커의 완전부착모형을 사용한 해석 결과를 실험 결과와 비교하였다. 이로부터 극한 반복하중을 받는 콘크리트-강재 구조물 수치해석에는 합리적인 앵커 부착-미끄러짐 모형이 반드시 사용되어야 한다는 것을 알 수 있었으며 본 연구에서 제안한 합성 연결모형을 이용하면 사실적으로 앵커의 부착-미끄러짐 현상을 모사할 수 있다는 것을 확인하였다.

In this paper, a numerical anchor bond-slip model is proposed to improve the numerical simulation of concrete-steel structures connected with steel anchor bolts and subjected to extreme cyclic loading. The suggested bond-slip model is composed of a group of nonlinear uniaxial connector elements and its parameters can be determined by calibrating the model with pull-out test data. Numerical analysis results from simulating a concrete foundation-steel column structure using the proposed bond-slip anchor model, which is implemented based on Abaqus elements, and the perfect-bond anchor model are compared with the experimental results. It is concluded that a reasonable anchor bond-slip model is required to realistically simulate concrete-steel structures subjected to extreme cyclic loading, and the proposed anchor bond-slip model shows acceptable performance in the present numerical analysis.

혼합구조체의 강-콘크리트 경계면은 하중이 증가함에 따라 합성작용 저하, 미세균열, 슬립 및 분리 등으로 비선형 거동을 나타내어 부분합성에 적합한 해석기법이 필요하다. 스터드의 상세해석을 통하여 이를 실현할 수 있으나 이는 해석 결과의 실효성에 비해 시간과 비용이 많이 투입되기 때문에 본 연구에서는 접합부의 경계비선형과 강-콘크리트의 재료비선형을 고려하여 더욱 정확한 강 콘크리트 혼합구조 해석기법을 제안하였다. 접합부의 경계면의 비선형성은 인터페이스 요소를 이용하여 모델링한다. 이를 위해 먼저 경계면의 비선형 거동 물성치를 산정하여야 한다. 경계면의 물성은 push-out test 등을 통하여 얻을 수 있는데 이는 기존에 연구되었던 실험결과를 이용하였다. 강과 콘크리트의 재료비선형을 고려하기 위해 콘크리트의 압축부는 Drucker-Prager 모델을 이용하고, 강재는 von-Mises 모델과 2개의 직선으로 이상화한 응력-변형률 관계를 적용하였다. 해석의 검증을 위해 프리스트레스트 콘크리트-강 혼합구조를 갖는 혼합거더의 정적 휨 거동에 관해 해석하여 기존의 실험결과와 비교하였다. 제안된 혼합구조 해석 기법을 이용하여 경계면의 비선형 모델을 변화시켜가면서 해석을 수행하여 강-콘크리트 혼합구조체의 거동을 분석하였다. 이후 경계면의 선형 해석방법과 완전부착을 가정하는 해석방법의 결과와 비교 분석하여 제안한 비선형 해석기법의 타당성을 검증하였다.

In this study, an analysis technique of hybrid girder considering nonlinearity of steel-concrete contact surface is presented. Steel-concrete hybrid girder shows partial-interaction behavior due to the deformation of shear connectors, slip and detachment at the interface, and cracks under the applied loads. Therefore, the partial-interaction approach becomes more reasonable. Contact surface is modeled by interface element and analyzed nonlinearly because of cost of time and effort to detailed model and analysis. Steel and Concrete are modeled considering non-linearity of materials. Material property of contact surface is obtained from push-out test and input to interface element. For the constitutive models, Drucker-Prager and smeared cracking model are used for concrete in compression and tension, respectively, and a von-Mises model is used for steel. This analysis technique is verified by comparing it with test results. Using verified analysis technique, various analyses are performed with different parameters such as nonlinear material property of interface element and prestress. The results are compared with linear analysis result and analysis result with the assumption of full-interaction.

본 연구에서는 f/L비가 다른 CFT 트러스 거더의 구조거동에 관한 실험 및 해석적 연구를 수행하기 위해서 2개의 실험체를 제작하였고, CFT 트러스 거더의 구조특성을 평가하기 위하여 휨실험을 수행하였다. ABAQUS에 의한 비선형 유한요소해석을 통해서 축력과 모멘트를 받는 CFT 부재의 비선형 재료모델을 비교분석하였다. CFT 부재의 구속 콘크리트 및 강재의 응력-변형률 모델은 많은 연구자들에 의해서 제시되어 왔다. 본 연구에서는 Mander, Sakino, Han, Susantha 및 Ellobody 등이 제안한 구속 콘크리트의 응력-변형률 모델을 적용하여 비선형해석을 수행하였고, 해석결과를 통해서 CFT 트러스 거더의 하중-처짐 관계, 하중-변형률 관계 등을 비교하였다. 하중-처짐 관계에서 Mander와 Susantha의 모델을 적용한 해석결과는 실험결과보다 약 12.0~13.8% 높은 하중을 예측하며, Sakino의 모델은 실험결과보다 약 7.6% 높은 하중을 예측하였다. Han과 Ellobody의 모델은 실험결과보다 약 0.2~1.2% 높은 하중을 예측하여 실험치와 가장 잘 맞는 결과를 보였다. 그러나 각 연구자의 응력-변형률 모델을 적용한 비선형 해석을 통해 산정된 하중-변형률 관계는 하중-처짐 관계와는 반대로 안전측의 결과를 보여 전반적으로 실험치보다 큰 수준의 변형률을 보였다.

Experimental and analytical studies are performed on the mechanical behavior of concrete-filled tubular(CFT) truss girders for different f/L ratios. Bending tests are conducted on two CFT truss girder specimens to determine fundamental structural characteristics such as the strength and deformation properties. Nonlinear material models for CFT members subjected to an axial compressive force are compared in this paper by using the nonlinear finite element program, ABAQUS. Previous researchers have proposed several nonlinear stress-strain models of confined concrete. In this study, the nonlinear analyses are performed applying several stress-strain models for confined concrete proposed by Mander, Sakino, Han, Susantha and Ellobody, and the results are compared with the experimental results in terms of load-deflection and load-strain relationships. Based on the comparisons of the load-deflection relationships, the models proposed by Mander and Susantha provide a maximum load about 12.0~13.8% higher and that by Sakino gives a maximum load about 7.6% higher than the experimental results. The models proposed by Han and Ellobody give a maximum load only about 0.2~1.2% higher than the test results, showing the best agreement among the proposed stress-strain models. However, the load-strain relations predicted by the existing models generally provide conservative results exhibiting larger strains than the experimental data.

A finite element analysis of end-to-end artery/PTFE anastomosis has been presented in this study to evaluate the distribution of compliance and stresses in the vicinity of the anastomosis due to any mismatch in compliance characteristics. The artery wall was assumed to be made of linear isotropic material in this simplified model and a nonlinear analysis and convergency study with respect to increasing meshed element numbers were performed with a mean artery pressure loading of the artery-PTFE model. Also, sub-modeling method was Introduced to progress the accuracy of the finite element analysis. The results are as follow : 1. A hypercompliant zone on the artery side was observed around 4.Omm from the anastomosis and a high hoop stresses in the wall of artery and PTFE was dominant. 2. An artery displays large deformation so that nonlinear analysis and sub-modeling method was used. 3. An anastomosis with the thinner thickness and larger diameter PTFE (B type) could reduce the compliance disagreement.

Monoleaflet polymer artificial heart valve was known to show remarkable improvement in antithrombosis and pressure drop compared with other type of artificial valve. In this investigation of monoleaflet heart valve the vertical and horizontal deflection pattern of polymer heart valve with three types of supporting members, straight member and two curved members were analysed using the large deformation nonlinear finite element method.