• 대한토목학회논문집
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• 제29권3A호
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• pp.181-188
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• 2009

본 연구에서는 현수교의 합리적인 시공방안 결정 및 구조안전성 평가에 대한 기초자료를 제시하였다. 기 연구된 현수교의 해석모델 및 신뢰성이론을 바탕으로 초기형상해석, 자유진동해석, 시공변수를 고려한 시공단계해석 및 신뢰성해석 등을 수행 할 수 있는 수치해석프로그램을 개발하였다. 현수교의 시공방안은 보강형의 시공순서, 시공방향 및 주경간과 측경간의 동시 시공성 등의 다양한 시공변수를 고려하여 설정하였다. 시공방안에 따른 동적시공단계해석은 작성된 해석프로그램에 의해 수행하였으며 주요부재의 응답특성을 검토하여 각각의 시공방안에 대한 장 단점을 제시하였다. 시공단계별 구조신뢰성해석은 자연적 불확실성을 고려하여 신뢰성지수 및 파괴확률을 산정함으로써, 설정된 시공방안에 따른 현수교의 안전성을 정량적으로 평가하였다. 아울러, 인위적 불확실성을 고려하여 산정된 해석결과에 대해 재평가하였으며, 시공단계 위험성의 주요 퍼센트 분포를 빈도수 히스토그램을 이용하여 제시하였다.

• Wind and Structures
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• 제38권1호
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• pp.43-58
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• 2024

To ensure the flutter stability of three-tower suspension bridges under skew wind, by using the computational procedure of 3D refined flutter analysis of long-span bridges under skew wind, in which structural nonlinearity, the static wind action(also known as the aerostatic effect) and the full-mode coupling effect etc., are fully considered, the flutter stability of a three-tower suspension bridge-the Taizhou Bridge over the Yangtze River in completion and during the deck erection is numerically investigated under the constant uniform skew wind, and the influences of skew wind and aerostatic effects on the flutter stability of the bridge under the service and construction conditions are assessed. The results show that the flutter critical wind speeds of three-tower suspension bridge under service and construction conditions fluctuate with the increase of wind yaw angle instead of a monotonous cosine rule as the decomposition method proposed, and reach the minimum mostly in the case of skew wind. Both the skew wind and aerostatic effects significantly reduce the flutter stability of three-tower suspension bridge under the service and construction conditions, and the combined skew wind and aerostatic effects further deteriorate the flutter stability. Both the skew wind and aerostatic effects do not change the evolution of flutter stability of the bridge during the deck erection, and compared to the service condition, they lead to a greater decrease of flutter critical wind speed of the bridge during deck erection, and the influence of the combined skew wind and aerostatic effects is more prominent. Therefore, the skew wind and aerostatic effects must be considered accurately in the flutter analysis of three-tower suspension bridges.

• 콘크리트학회논문집
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• 제16권6호
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• pp.867-873
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• 2004

It has been known that debonding failures between CFS(Carbon Fiber Sheet) and concrete in the strengthened RC beams are initiated by the peeling of the sheets in the region of combined large moment and shear forces, being accompanied by the large shear deformation after flexural cracks. These shear deformation effects are seldom occurred in small-scale model tests, but debondings due to the large shear deformation effects are often observed in a full-scale model tests. The premature debonding failure of CFS, therefore, must be avoided to confirm the design strength of full-scale RC beam in strengthening designs. The reinforcing details, so- called 'U-Shape fiber wrap at mid-span' which wrapped the RC flexural members around the webs and tension face at critical section with CFS additionally, were proposed in this study to prevent the debonding of CFS. Other reinforcing detail, so called 'U-Shape fiber wrap at beam end' were included in this tests and comparisons were made between them.

• 한국공간구조학회논문집
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• 제19권4호
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• pp.69-76
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• 2019

A stadium roof that uses the pin-jointed spatial truss system has to be designed by taking into account the unstable phenomenon due to the geometrical non-linearity of the long span. This phenomenon is mainly studied in the single-free-node model (SFN) or double-free-node model (DFN). Unlike the simple SFN model, the more complex DFN model has a higher order of characteristic equations, making analysis of the system's stability complicated. However, various symmetric conditions can allow limited analysis of these problems. Thus, this research looks at the stability of the DFN model which is assumed to be symmetric in shape, and its load and equilibrium state. Its governing system is expressed by nonlinear differential equations to show the double Duffing effect. To investigate the dynamic behavior and characteristics, we normalize the system of the model in terms of space and time. The equilibrium points of the system unloaded or symmetrically loaded are calculated exactly. Furthermore, the stability of these points via the roots of the characteristic equation of a Jacobian matrix are classified.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.879-884
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• 2001

The use of recycled-aggregate concrete is increasing faster than the development of appropriate design recommendations. In addition, recycled-aggregate and higher compressive strengths are two of the most desired characteristics to improve the use of concrete as a construction material. The paper reports limited experimental data on the shear capacity of high-strength recycled aggregate concrete beams. Ten beams were tested to determine their diagonal cracking and ultimate shear capacities. The variable in the test program were concrete strength(300, 500 and 700kgf/$cm^{2}$), and shear span/depth ratio (a/d : 2.0, 3.0 and 4.0). Test results indicate that the ACI Building code prediction of Eq.(11-3) and (11-5) for high-strength recycled aggregate concretes are unconservative for all beams (with concrete strength 300, 500 and 700kgf/$cm^{2}$, a/d ratios 2.0, 3.0 and 4.0). But Zsutty Equation for high-strength recycled aggregate concretes is conservative for all beams. The results of the experimental investigation on the cracking patterns for beams show that the angle that the critical inclined crack makes with the horizontal axis decreases with increasing a/d.

• Smart Structures and Systems
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• 제14권5호
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• pp.917-942
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• 2014

Multivariate statistics based damage detection algorithms employed in conjunction with novel sensing technologies are attracting more attention for long term Structural Health Monitoring of civil infrastructure. In this study, two practical data driven methods are investigated utilizing strain data captured from a 4-span bridge model by Fiber Bragg Grating (FBG) sensors as part of a bridge health monitoring study. The most common and critical bridge damage scenarios were simulated on the representative bridge model equipped with FBG sensors. A high speed FBG interrogator system is developed by the authors to collect the strain responses under moving vehicle loads using FBG sensors. Two data driven methods, Moving Principal Component Analysis (MPCA) and Moving Cross Correlation Analysis (MCCA), are coded and implemented to handle and process the large amount of data. The efficiency of the SHM system with FBG sensors, MPCA and MCCA methods for detecting and localizing damage is explored with several experiments. Based on the findings presented in this paper, the MPCA and MCCA coupled with FBG sensors can be deemed to deliver promising results to detect both local and global damage implemented on the bridge structure.

• Journal of Korean Neurosurgical Society
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• 제41권4호
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• pp.217-223
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• 2007

Objective : The apparent increase in the incidence of the intracranial meningiomas in the elderly is due in part to improved diagnostic tools and improved span of life. The authors carried out a retrospect study to validate the use of the Clinical-Radiological Grading System [CRGS] as a clinical tool to orientate surgical decision making in elderly patients and to explore prognostic factors of survival. Methods : From January 1997 to January 2006, the authors consecutively recruited and surgically treated 20 patients older than 65 years of age with radiologic findings of intracranial meningiomas and a preoperative evaluation based on the CRGS. Results : High CRGS score was associated with a higher probability of good outcome [p=0.004] and a lower probability of postoperative complications [p=0.049]. Among the different subset items of the CRGS score, larger maximum tumor diameters [$D{\geqq}4cm$] and the presence of a severe peritumoral edema were associated with incidence rate of postoperative poor outcome and complications [p<0.05]. Additionally, the critical location of the tumor was also correlated with poor outcome [p<0.05]. Conclusion : A CRGS score higher than 13 is a good prognostic indication of survival. The CRGS score is a useful and practical tool for the selection of elderly patients affected by intracranial meningiomas as surgical candidates.

• Steel and Composite Structures
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• 제27권5호
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• pp.545-554
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• 2018

This study presents a novel method of improving the strength and stiffness of cold-formed steel (CFS) beams. Flexural members are primary members in most of the structures. Hence, there is an urgent need in the CFS industry to look beyond the conventional CFS beam sections and develop novel techniques to address the severe local buckling problems that exist in CFS flexural members. The primary objective of this study was to develop new CFS composite beam sections with improved structural performance and economy. This paper presents an experimental study conducted on different CFS composite beams with simply supported end conditions under four point loading. Material properties and geometric imperfections of the models were measured. The test strengths of the models are compared with the design strengths predicted by using Australian/New Zealand Standard for cold-formed steel structures. Furthermore, to ensure high precision testing, a special testing rig was also developed for testing of long span beams. The description of test models, testing rig features and test results are presented here. For better interpretation of results, a comparison of the test results with a hot rolled section is also presented. The test results have shown that the proposed CFS composite beams are promising both in terms of better structural performance as well as economy.

• 한국공간구조학회논문집
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• 제6권2호
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• pp.93-105
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• 2006

본 연구는 보강 조적벽체의 지진거동에 대한 실험적 연구로써, 기둥의 보강, 조적벽체의 보강, 횡하중 높이에 대한 역학적 특성을 분석하였다. 시험체는 구멍이 있는 콘크리트 블록으로 만들었고, 전단 스팬비, 횡하중 높이의 영향, 보강기둥 및 벽체 철근 보강비에 대한 구조적 특성을 파악할 수 있도록 하였다. 벽체의 횡력에 대한 하중점의 벽체 높이의 0.67, 1.08 및 1.1배로 하였다. 수평방향의 철근비는 0, 0.08, 0.18, 수직 방향의 철근비는 0.18, 0.36, 0.64로 하였다.

• 건축역사연구
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• 제10권2호
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• pp.55-71
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• 2001

This study reviewed the preservation status of the Early Western Style Architecture in Korea based on the on-site research of church buildings which are registered as National Cultural Properties. I have investigated 21 church buildings regarding the frequency, content and concept of restoration. The results are summarized as follows First, the churches have been restored extensively in every 17 years on the average. Second, the main restorations are replacement of bricks, painting, waterproofing, repair of roof and timber. And the main changes are extension of plan, removal of Interior posts, and replacement of floor. Third, the main concept of restorations are historical restoration(62%), critical restoration(23%), stylistic restoration(14%). Forth, the category of restoration have been changed, that is extending of incompletion (1st stage), functional improvement and extension of the span of life(2nd stage), improvement of facilities(3rd stage), restoration to the original state and conservation(4th stage). Fifth, the issues of repairing techniques are revival and replacement of weathered bricks, the removal of painting, and structural reinforcement. This study will be able to be used as the fundamental materials to improve the techniques of restoration of Early Western style masonry buildings.