• Structural Monitoring and Maintenance
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• 제6권4호
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• pp.365-387
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• 2019

This study aims to provide useful information on the fatigue assessment of a top-tensioned riser (TTR) subjected to vortex-induced vibration (VIV) by performing parametric study. The effects of principal design parameters, i.e., riser diameter, wall thickness, water depth (related to riser length), top tension, current velocity, and shear rate (or shear profile of current) are investigated. To prepare the base model of TTR for parametric studies, three (3) riser modelling techniques in the OrcaFlex were investigated and validated against a reference model by Knardahl (2012). The selected riser model was used to perform parametric studies to investigate the effects of design parameters on the VIV fatigue damage of TTR. From the obtained comparison results of VIV analysis, it was demonstrated that a model with a single line model ending at the lower flex joint (LFJ) and pinned connection with finite rotation stiffness to simulate the LFJ properties at the bottom end of the line model produced acceptable prediction. Moreover, it was suitable for VIV analysis purposes. Findings from parametric studies showed that VIV fatigue damage increased with increasing current velocity, riser outer diameter and water depth, and decreased with increasing shear rate and top tension of riser. With regard to the effects of wall thickness, it was not significant to VIV fatigue damage of TTR. The detailed outcomes were documented with parametric study results.

• 한국컴퓨터정보학회논문지
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• 제20권1호
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• pp.39-48
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• 2015

본 연구는 벽화마을 3곳을 중심으로 문제점과 발전방향을 모색하고 디지털 콘텐츠 활용 방안을 제시하였다. 논의는 크게 세 가지 관점에서 이루어졌다. 첫째, 현재의 벽화마을은 지리적 문화적 이점을 살릴 수 있는 정체성을 갖추지 못하고 있는 실정이다. 중장기적으로 볼 때, 브랜드화가 대안이 되어야 한다. 둘째, 미적 측면에서 보았을 때, 대부분의 벽화마을은 페인팅벽화 위주로 되어 있다. 도자 벽화가 활성화 되어야 한다. 셋째, 관광연계성의 측면에서 보았을 때, 다양한 행사와 축제가 있어야 한다. 또한 관광객이 스마트폰 앱을 활용하여 벽화의 위치와 주변의 볼거리, 먹거리, 숙박, 편의시설을 쉽게 접할 수 있는 디지털 콘텐츠화가 이루어져야 한다. 벽화마을은 이제 내외국인의 탐방 주제로 자리를 잡아가고 있다. 보다 많은 관광객이 벽화마을을 찾는다면 지역 경제에도 도움이 될 것이며, 벽화마을에 사는 주민에게는 자긍심을 심어줄 것이다.

• Steel and Composite Structures
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• 제23권4호
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• pp.409-420
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• 2017

This paper theoretically studies the cyclic behavior of hybrid connections between steel coupling beams and concrete shear walls with embedded steel columns. Finite element models of connections with long and short embedded steel columns are built in ABAQUS and validated against the test results in the companion paper. Parametric studies are carried out using the validated FE model to determine the key influencing factors on the load-bearing capacity of connections. A close-form solution of the load-bearing capacity of connections is proposed by considering the contributions from the compressive strength of concrete at the interface between the embedded beam and concrete, shear yielding of column web in the tensile region, and shear capacity of column web and concrete in joint zone. The results show that the bond slip between embedded steel members and concrete should be considered which can be simulated by defining contact boundary conditions. It is found that the loadbearing capacity of connections strongly depends on the section height, flange width and web thickness of the embedded column. The accuracy of the proposed calculation method is validated against test results and also verified against FE results (with differences within 10%). It is recommended that embedded steel columns should be placed along the entire height of shear walls to facilitate construction and enhance the ductility. The thickness and section height of embedded columns should be increased to enhance the load-bearing capacity of connections. The stirrups in the joint zone should be strengthened and embedded columns with very small section height should be avoided.

• 대한토목학회논문집
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• 제42권1호
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• pp.1-9
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• 2022

반일체식교대교량은 일체식 교대교량의 한 형식이다. 이 교량은 상부구조에서 신축조인트를 제거한 것으로 완전일체식 교대교량이 적용하지 못한 상황에 사용할 수 있으며, 유지관리 성능이 우수하고, 하부구조를 경제적으로 시공할 수 있다. 이 연구는 교대벽체의 일부를 PSC 거더의 단부 벽체형 블록 형태로 제작한 반일체식교대교량에 대한 것으로, 온도신축에 따라 종방향 이동에 저항 역할을 하는 프리캐스트 블록을 활용한 PSC 거더이다. 프리캐스트 블록 PSC 거더는 거더 단부에 프리캐스트 블록을 일체 타설하여 제작하며, 교대벽체 위에 단순거치한 후 무수축 콘크리트와 합성하는 방식으로 시공한다. 따라서 본 연구는 재하실험을 통해 구조계산한 결과에 비교하고자 하며, 나아가 실제 시공된 반일체식교대교량의 토압 및 상부구조 변위 계측하여 이를 분석을 통한 구조성능 평가하였다.

• 콘크리트학회논문집
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• 제14권5호
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• pp.734-741
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• 2002

중앙부 철골조와 단부 RC조로 이루어진 혼합구조보인 RS 보와 RC 기둥으로 이루어진 접합부의 비탄성 거동 및 내진성능을 구명하기 위하여 반복가력에 의한 접합부 실험을 진행하였다. 본 연구는 RC-RS 접합부의 모멘트비를 변수로 하여 두 개의 내부접합부와 한 개의 외부접합부 등 총 3개의 시험체를 제작하여 실험을 진행하였다. 실험결과, 강도와 연성능력은 충분히 발휘하였으나, 접합부의 강성은 부족한 결과를 나타내었다. 이는 RS 보를 구성하는 철골보와 RC 보를 연결하는 강재매입구간에서의 철골 보의 미끄러짐에 의한 변위의 증가로 인하여 강성의 저하가 발생한 것으로 판단된다. 또한 Hawkins의 제안안에 의한RC-RS 접합부의 내진성능을 평가해 본 결과, 접합부의 초기강성의 부족으로 부재각 0.5 %에서의 공칭강도의 발현은 만족하지 못하였으나, 그외의 내진성능 평가지표인 강도유지능력, 상대 에너지소산비 및 종국후 초기강성비나 초기강도비 등의 측면에서는 우수한 능력을 발휘하였다. 따라서 구조물에서 RC-RS 접합부를 적용할 경우, RC 코어 월과 같은 초기 횡 강성을 보완할 수 있는 적절한 구조시스템과 병행하여 적용하면 강진지역의 구조물에도 충분히 적용이 가능하다고 판단된다.

• 한국구조물진단유지관리공학회 논문집
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• 제26권6호
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• pp.128-138
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• 2022

본 연구에서는 원심성형으로 제작된 100MPa이상의 초고강도 콘크리트 각형보를 피암터널의 상부구조로 적용하기 위해 원심성형 보를 부모멘트 영역인 하부구조와 일체화시킨 우각부 단면에 대한 구조적인 안전성을 검증하는 것을 목적으로 실물크기의 시험체를 제작하고 하중재하시험 및 해석연구를 수행하였다. 피암터널 표준모델에 대해 시방규정에 의한 하중조합으로 설계하였을 때 상부슬래브 단부의 우각부에 최대 모멘트가 발생하는 것과 같은 효과를 기대하기 위하여 수정된 캔틸레버 형식의 구조모형 시험체를 제작하여 우각부 고정연결방법에 대한 성능과 최적연결시공법을 도출하기 위한 연구가 수행되었다. 실험결과, 개발된 고정연결장치는 형상과 연결방식에 상관없이 모두 안정적인 휨 거동을 나타내었다. 또한, 시험체는 파괴시까지 고정연결장치에 의해 연결된 원심성형 PSC 각형보와 상부슬래브가 일체 거동을 하는 것으로 나타나 고정연결장치의 성능이 매우 우수한 것으로 확인되었다. FEM 해석에 따른 우각부 해석모델의 거동은 재하실험과 비교하여 강성이 미소하게 나타났으나 전체적인 거동이 거의 유사하게 나타났다. 따라서, 본 연구에서 개발한 원심성형 각형보와 벽체간의 우각부 연결부를 시공함에 있어 구조적으로 문제가 없을 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제44권3호
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• pp.249-260
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• 2012

Main focus of the combined nuclear research activities at Aachen University (RWTH) and the Research Center J$\ddot{u}$lich (J$\ddot{U}$LICH) is the experimental and analytical investigation of containment phenomena and processes. We are deeply convinced that reliable simulations for operation, design basis and beyond-design basis accidents of nuclear power plants need the application of so-called lumped-parameter (LP) based codes as well as computational fluid dynamics (CFD) codes in an indispensable manner. The LP code being used at our institutions is the GRS code COCOSYS and the CFD tool is ANSYS CFX mostly used in German nuclear research. Both codes are applied for safety analyses especially of beyond design accidents. Focal point of the work is containment thermal-hydraulics, but source term relevant investigations for aerosol and iodine behavior are performed as well. To increase the capability of COCOSYS and CFX detailed models for specific features, e.g. recombiner behavior including chimney effect, building condenser, and wall condensation are developed and validated against facilities at different scales. The close connection between analytical and experimental activities is notable and identifying feature of the RWTH/J$\ddot{U}$LICH activities.

• Structural Engineering and Mechanics
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• 제49권2호
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• pp.237-259
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• 2014

Wind-induced failure around screwed connections has been documented in roof and wall cladding systems made with steel sheet cold-formed panels during high wind events. Previous research has found that low cycle fatigue caused by stress concentration and fluctuating wind loads is responsible for most such failures. A dynamic load protocol was employed in this work to represent fatigue under wind effects. A finite element model and fatigue criteria were implemented and compared with laboratory experiments in order to predict the fatigue failure associated with fluctuating wind loads. Results are used to develop an analytical model which can be employed for the fatigue analysis of steel cold-formed cladding systems. Existing three dimensional fatigue criteria are implemented and correlated with fatigue damage observed on steel claddings. Parametric studies are used to formulate suitable yet simple fatigue criteria. Fatigue failure is predicted in different configurations of loads, types of connections, and thicknesses of steel folded plate cladding. The analytical model, which correlated with experimental results reported in a companion paper, was validated for the fatigue life prediction and failure mechanism of different connection types and thicknesses of cold-formed steel cladding.

• Tuberculosis and Respiratory Diseases
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• 제69권3호
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• pp.191-195
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• 2010

Abnormally located liver tissue has been described in the vicinity of the liver proper, near anatomical structures such as the gallbladder, the umbilical fossa, the adrenal gland, the pancreas, and the spleen. Supradiaphragmatic ectopic liver is a rare finding, but has been reported to have been found in the intrathoracic cavity and in the pericardium. In the majority of supradiaphragmatic ectopic liver cases, there was an accompanying transdiaphragmatic pedicle of the main liver body into the abdominal cavity. In a minority of supradiaphramatic ectopic liver cases, the liver was completely separated from the abdominal cavity without a connection between the thorax and the abdomen, with accompanying diaphragmatic anomalies. We describe one case of intrathoracic ectopic liver in a patient with a previous history of lower chest wall trauma, and a brief review of the English-language medical literature on this topic.

• 한국안전학회지
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• 제32권3호
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• pp.66-73
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• 2017

This study examined the structural behavior of bracket scaffolds reflecting the influence of bracket's deflection. Even though the supporting condition of bracket scaffolds is different to that of general earth-supported scaffolds, there is no clear standards about the installation of bracket scaffolds. To compare the structural behaviors of the earth-supported scaffolds without settlements in columns and those of bracket scaffolds installed on the bracket structure, the finite element analysis was performed. The results show that the differential settlement between the scaffold columns installed on the bracket was occurred due to the deflection of the bracket. The differential settlement gave birth to remarkable secondary stress to the scaffold columns. It is resonable to locate all scaffold columns on the brackets, and if unavoidable situation is faced at a site, the horizontal members should not placed alone without columns on the brackets. Moreover, the structural analysis should be performed to ensure structural safety of bracket scaffolds before installation. In addition, the location of wall connection to the structures is recommended to the scaffolds columns installed on the brackets.