• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.399-406
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• 1999

Recently, the construction of the several highway bridges in the karst area have encountered severe problems associated with cavities and sinkholes. To solve this problems, it is important to understand the distribution characteristics of cavities in the construction site on limestone area. This paper briefly describes the different types, the distribution control factors and the infill sediment types of lime-cavities in the study area, bridge site in the karst area and propose the effective method of survey design. Cavity system may be divided into two main groups, 1)'slot and cave system'and 2)'sinkhole and cave system'. And the shape, the size and the distribution pattern of cavity are controlled by three main factors - rock type, geological structure and ground water condition. Additionally, infill sediment may be considered as one of the important design factors for foundation design and divided into four types by sediment properties. There are geophysical thechnics and geologic survey and drilling test, etc. by the survey method to interpretate characteristics of cavity system, and this methods are optimally designed at the site investigation stage.

• 한국조경학회지
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• 제30권2호
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• pp.1-11
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• 2002

The purpose of this study is to investigate landscape image and define elements of difference in visual preference of bridges on the Han River. To do this end, video was used as a media for the evaluation of the landscape image of 16 bridges on the Han River using a Semantic Differential scale. Data is collected by 50 students from Woosuk University, majoring landscape architecture. Final analysis utilized a total of 704 samples of data. Data is analyzed through descriptive statistics, and spatial image is analyzed by factor analysis algorithm Principle component analysis using Varimax method is applied far extraction and factor rotation. T-test is used to find the difference between the bridge type of preference with the data of factor score. Logistic regression is used to select the factors that influences the visual preference among the image factors. The results of this study can be summarized as follows; The image of whole bridges on the Han River is somewhat orderly, sequential and open. The degree of visual preference of unique bridge type is higher than normal but there are some differences in visual preference within the same type of structure. This suggests that the surrounding landscape is one of the important factor for visual preference. Factors covering the image of bridge are found to be 'aesthetic',　'structure','spatial factor', and 'shape'. Total variance is obtained as 60.4%. The aesthetic variables are the most important factor for visual preference and the structural factor presents no significant difference in visual preference between more preferred and less preferred bridges. Since the collapse of Songsu Bridge, we thought the structural factor is very important but the results of this study suggest that it is more important to consider the aesthetic and spatial factors of the bridge to increase the visual preference when planning and designing bridges. Simulations with more detailed data about surroundings should be utilized practical design.

• 한국철도학회논문집
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• 제12권1호
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• pp.129-134
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• 2009

공용기간동안 철도교량의 안전성 및 사용성을 확보하기 위해서는 지속적인 감시를 통하여 교량의 구조적 성능을 유지하는 것이 필요하다. 구조물의 구조적 건전성을 감시하기 위하여 현재까지 개발된 대부분의 방법들은 모달 응답을 이용하고 있으나, 이러한 모달응답은 별도의 추출 과정이 필요하며 실제 구조물에서 얻을 수 있는 수가 제한된 다는 단점이 있다. 이 논문에서는 열차이동하중으로 인한 시간영역의 변형형상을 이용하여 자유진동응답에 기반한 손상평가방법의 적용성을 검토하였다. 검토된 방법은 이동하중으로 인한 시간영역의 변형응답을 이용하므로 별도의 모달 응답 추출과정이 필요 없어 실제 구조물에 적용이 용이하다. 제시된 방법의 적용성은 단순판형교 수치예제를 이용하여 검증하였다.

• Computers and Concrete
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• 제15권2호
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• pp.231-257
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• 2015

This paper discusses the spatial variability of the carbonation depth caused by the mesoscopic structure of the concrete and the influence of the spatial variability on the thickness of the concrete cover. To conduct the research, a method to generate the random aggregate structure (RAS) based on polygonal particles and a simplified numerical model of the concrete carbonation at meso-scale are firstly developed. Based on the method and model, the effect of the aggregate properties including shape, content and gradation on the spatial variability of the carbonation depth is comprehensively studied. The results show that a larger degree of the spatial variability will be obtained by using (1) the aggregates with a larger aspect ratio; (2) a larger aggregate content; (3) the gradation which has more large particles. The proper sample size and model size used in the analysis are also studied. Finally, a case study is conducted to demonstrate the influence of the spatial variability of the carbonation depth on the proper thickness of the concrete cover. The research in this paper not only provides suggestions on how to decrease the spatial variability, but also proposes the method to consider the effect of the spatial variability in designing the thickness of the concrete cover.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.20-27
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• 2005

Solar radiation causes non-uniform temperature distribution in the structure, depending on the shape of the structure and its shadows. Especially in cases of curved steel box girder bridges, non-uniform temperature distribution due to solar radiation can reduce bridge life and serviceability when combined with another load combination. In this study, the method for predicting the temperature distribution of curved bridges developed by Kim et al., was used to predict the non-uniform temperature distribution which served as a basis for structural analysis of 3-D bridge behavior. In order to seek the most unfavorable conditions of solar radiation, observation data from the Korea Meteorological Administration for solar radiation were analyzed. The region of the most high solar radiation condition was selected and its one year variation of the solar radiation data was considered. From this analysis, the most unfavorable solar radiation condition with lower solar altitude and intense solar radiation was selected. Based on the selected solar radiation condition, structural behavior of curved bridges with diverse bridge direction, span length, radius and support conditions are analyzed.

• Computers and Concrete
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• 제2권2호
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• pp.125-146
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• 2005

The objective of this paper is setting out, for a cable-stayed bridge with a curtain suspension, a method to determine the modes of vibration of the structure. The system of differential equations governing the vibrations of the bridge, derived by means of a variational formulation in a nonlinear field, is reported in Appendix C. The whole analysis results from the application of Hamilton's principle, using the expressions of potential and kinetic energies and of the virtual work made by viscous damping forces of the various parts of the bridge (Monaco and Fiore 2003). This paper focuses on the equation concerning the transversal motion of the girder of the cable-stayed bridge and in particular on its final form obtained, restrictedly to the linear case, neglecting some quantities affecting the solution in a non-remarkable way. In the hypotheses of normal mode of vibration and of steady-state, we propose the resolution of this equation by a particular method based on a numerical approach. Respecting the boundary conditions, we derive, for each mode of vibration, the corresponding frequency, both natural and damped, the shape-function of the girder axis and the exponential function governing the variability of motion amplitude in time. Finally the results so obtained are compared with those deriving from the dynamic analysis performed by a finite elements calculation program.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.277-282
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• 2007

In recent years, dramatic advances in information technology have motivated the construction industry to improve its productivity. Most construction companies are trying to utilize some new information technologies for enhancing the structure quality, shortening construction time, and reducing the construction cost. Digital Mock-Up (DMU) technology utilizes 3D CAD/CAM system that shows the shape of a structure on the computer screen. By modeling and assembling the structure in 3D dimensional environments, some errors in design can be found before or during construction. In this paper, DMU technology was applied to the detail design and construction of In-Cheon Bridge and its effectiveness was evaluated. All components of a PSC box girder segment were modeled and assembled by using of 3D CAD tools and then, some interferences between components and errors were found and revised appropriately before construction. Consequently, DMU technology would improve the quality of the structure and reduce time and cost for construction.

• 한국조경학회지
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• 제30권5호
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• pp.31-38
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• 2002

This study attempts to grasp the correlation between the image of bridges and bridge landscapes with their surroundings during day and nighttime viewing, and to understand the psychological influence of nighttime lighting through quantitative analysis. In addition, it presents a design to construct bridges in order to increase viewers enjoyment of bridge landscapes lit at night. To attain this objective and contrive generalization of the results, this paper selects 8 of 9 bridges with lightings in Seoul and excludes bridges constructed by 2004. The criteria for selection of the viewpoints is that each must be within easy reach of bridges, and must allow viewers to recognize surrounding landscape details both in daylight and at night. As well, the pictures of bridges are taken in the terraced land by the riverside. The study selects 16 pictures, judged to be of similar quality and angle, to establish the conditions of luminosity, color, definition and angle. The results are as follows. First, viewers preferences of night landscapes are higher than day landscapes due to the effect of lighting. By day, viewers preferred bridges with various structures such as cable-stayed bridges and arch bridges more than simple bridges like girder bridges. Viewers also indicated preferences for lightings which feature a unique color and which are harmonized with their surroundings. Second, components representing the images of bridge landscape are classified into three types, 'beauty', 'system' and 'agreeableness'. Third, the factors affecting preference are the shape of bridge by day and lighting at night. Esthetic appeal is the most important factor in visual preference so each bridges own esthetic appeal and surroundings must be considered. Thus, a complete plan must be created which considers safety, beauty and the local surroundings. In addition, when the lighting of a bridge is selected, the design of the bridge landscape must consider various lighting schemes to harmonize the upper and lower parts of the structure. At this point, the study reveals the basic elements of bridge planning in order to increase appreciation of the bridge landscape.

• 대한치과보철학회지
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• 제36권1호
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• pp.104-119
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• 1998

The purpose of this study was pertinent design of the framework of the fixed bone anchored bridge using implants in the edentulous mandible through analysis of stress distribution by the three dimensional finite element analysis method. The results were as follows: 1. The L-shaped framework was favorable in restoring the edentulous mandible by implants and fixed bone anchored bridge. 2. The structure of the framework should be designed to endure the occlusal load because of stress concentration at the most distal abutment of the framework. 3. The stress at the distal implant where cantilever starts was twice as much as that of other portions. 4. Compressive stress was generated on the framework of the mesial side of the distal implant and extrusive force was induced to the mesially positioned implants. 5. The height of vertical plate was high as possible as can be to distribute stresses concentrating bucco-lingually and labio-lingually in the framework between abutments, 6. Reinforcement of the horizontal plate thickness was needed because stress was loaded more on the horizontal plate than on the vertical plate of the framework. 7. Lengthening of the vertical plate can compensate for any limitations in horizontal plate width.

• Wind and Structures
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• 제19권3호
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• pp.233-247
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• 2014

Vortex-induced oscillation is a type of aeroelastic phenomenon, to which extended structures such as long-span bridges are most susceptible. The vortex-induced vibration (VIV) behaviors of a concerned bridge were investigated conventionally in virtue of wind tunnel tests on string-mounted sectional models. This necessitates the building of a linkage between the response of the sectional model and that of the prototype structure. Although many released literatures have related to this issue and provided suggestions, there is a lack of consistency among them. In this study, some theoretical models describing the vortex-induced structural motion, including the linear empirical model, the nonlinear empirical model and the modified (or generalized) nonlinear empirical model, are firstly reviewed. Then, the concept of equivalent mass density is introduced based on the principle that an equal input of energy should result in identical structural amplitudes. Based on these, the theoretical linkages between the amplitude of a section model and that corresponding to the prototype bridge are discussed with different analytical models. Theoretical derivation indicates that such connections are dependent mainly on two factors, one is the presupposed shape of deformation, and the other is the theoretical VIV model employed. The theoretical analysis in this study shows that, in comparison to the nonlinear empirical models, the linear one can result in obvious larger estimations of the full bridges' responses, especially in cases of cable-stayed bridges.