• Journal of Korean Society of Steel Construction
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• v.16 no.3 s.70
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• pp.333-344
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• 2004

In civil engineering applications, the establishment of standards and procedures for analysis, design, fabrication, construction, and quality control are essential in facilitating the economic and efficient use of composite materials. Many bridge systems, including girders. cross beams, and concrete decks, function as specially orthotropic plates. in general, the analytical solution for such complex systems is very difficult to achieve. Thus, the finite difference method is used for the analysis of the problem. The rate of tensile strength reduction due to increased size is considered. Strength reduction is necessary to ensure the safe design of building structures. This paper suggests the use of a strength-failure analysis procedure using the reduced tensile strength. A numerical study is conducted for different cases. The Tasi-Wu failure criterion for stress space is also used.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.435-442
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• 2002

본 연구에서는 사장교의 제어기법 개발을 위한 구조물로 제공되는 벤치마크(benchmark) 사장교에 대해 복합제어 기법을 적용하였다. 이 벤치마크 문제에서는 2003년 완공 예정으로 미국 Missouri 주에 건설 중인 Cape Girardeau 교를 대상 구조물로 고려하였다. Cape Girardeau 교는 New Madrid 지진구역에 위치하고, Mississippi 강을 횡단하는 주요 교량이라는 점 때문에 설계단계에서부터 내진 문제에 대하여 자세하게 고려되었다. 상세 설계도면을 기반으로 하여 교량의 전체적인 거동 특성을 정확하게 나타낼 수 있는 3차원 모델이 만들어졌고, 사장교의 제어 성능에 관련된 평가 기준이 수립되었다. 본 연구에서 사용한 복합제어 기법이란 지진하중으로 인해 구조물에 발생되는 하중을 줄이기 위한 수동제어 기법과 상판변위와 같은 구조물의 응답을 추가적으로 제어하기 위한 능동제어 기법이 결합된 제어방법이다. 수동제어 장치로는 현재 일반적으로 많이 사용되고 있는 납고무받침(lead rubber bearing)을 사용하였다. 능동제어 방법에는 $H_2$/LQG 제어 알고리듬(algorithm)을 사용하였다. 수치해석 결과 제안방법의 성능은 수동제어 방법에 비해 매우 효과적이며, 능동제어 방법에 비해서는 좀더 좋은 제어성능을 나타내었다. 또한, 복합제어 방법은 수동제어 부분 때문에 능동제어 방법에 비해 좀더 신뢰할 수 있는 제어 방법이다. 따라서 제안된 제어방법은 지진하중을 받는 사장교의 제어를 위해 효과적으로 사용될 수 있다.

• Composites Research
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• v.12 no.4
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• pp.33-41
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• 1999

In this paper, a simple but accurate method of vibration analysis of structural elements with or without attached mass/masses is presented. The method used has been developed by D.H., Kim since 1974. This method is very effective for the plates with arbitrary conditions and irregular sections. This method is applied to the special orthotropic plate with two opposite edges simply supported and the other two opposite edges free. Such plate represents the most of the simply supported bridges/decks, including concrete and girders-cross beam systems. Detailed illustration is given for beams and plates for easy understanding. Some laminate orientation for which the special orthotropic equations can be applied are identified.

• International Journal of Highway Engineering
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• v.6 no.1 s.19
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• pp.13-23
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• 2004

This paper presents the results of a study that was performed to evaluate structural behaviors and related distress of asphalt pavements on concrete bridge deck based on the visual inspection and 3-dimensional finite element analysis. As a result, three most failure types were found such as permanent deformation, potholes, and fatigue crackings. In addition, the failure mechanisms of different types of concrete bridge deck were investigated. An increase in fatigue of asphalt pavements on concrete bridge deck was observed and confirmed by the results from the visual inspections. In consequence, the aging and stripping of asphalt surfacing materials are relatively dominant factors on fatigue rather than traffic loadings.

• Journal of the Korean Society for Railway
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• v.20 no.4
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• pp.521-528
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• 2017

In this study, vertical loading tests were conducted to investigate the nonlinear behaviors of the fastening systems that have generally been used in the concrete track of domestic railway lines. Nonlinear load-displacement curve models were derived based on the test results. The uplift forces generated in the fastening systems were evaluated by applying the derived nonlinear models as well as the existing linear models. The influence of the factors on the maximum uplift force of the fastening system was analyzed through a parameter study on the distance between neighboring sleepers, the horizontal distance between the center of the bearing and the nearest fastening system from the deck end, and the height of the bridge girder. From the evaluation results it is known that, for economical track and bridge design, due to deck end deformation, it is necessary to consider the nonlinear behavior of the fastening system in the calculation of the uplift force of the fastening systems.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.793-804
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• 2006

Various PSC and steel-concrete composite railway bridges are being developed for short-medium spans with structural and economic efficiency. According to the design concept, the prestressed composite girder bridge has the advantages of being lightweight and having low girder depth, with the capacity for long spans. However, the dynamic behavior under a passing train is one of the critical issues concerning these railway bridges designed with more flexibility. Therefore, it is very important to evaluate the modal parameters before performing dynamic analyses. In this paper, real-scale prestressed composite girders were fabricated as a test model and modal testing was carried out to evaluate modal parameters including natural frequency and modal damping ratio. During the modal testing, a digitally controlled vibration exciter as well as an impact hammer was applied to obtain frequency-response functions, and the modal parameters were also evaluated after the fracture of test models. With application of reliable properties from modal tests, the estimation of dynamic performances of prestressed composite girder railway bridges can be obtained from various parametric studies on dynamic behavior under the passage of a moving train.

• Journal of Digital Contents Society
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• v.18 no.6
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• pp.1041-1047
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• 2017

There are many methods for surveying the status of a road, and the use of unmanned aerial vehicle (UAV) photo is one such method. When the UAV images are too large to be processed and suspected to be redundant, a texture extraction technique is used to transform the data into a reduced set of feature representations. This is an important task in 3D simulation using UAV images because a huge amount of data can be inputted. This paper presents a texture extraction method from UAV images to obtain high-resolution images of bridges. The proposed method is in three steps: firstly, we use the 3D bridge model from the V-World database; secondly, textures are extracted from oriented UAV images; and finally, the extracted textures from each image are blended. The result of our study can be used to update V-World textures to a high-resolution image.

• Magazine of the Korea Concrete Institute
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• v.8 no.1
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• pp.138-144
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• 1996

At present, waterproof is absolutely needed to minimize the carbonation of bridge decks in Kor ea. In this research indoor experiments for penetrative waterproof admixture out of available methods are carried out to evaluate the resisting characteristics against natural arid artificial car bona ting conditions. The test results show that the optimal time of waterproof is 14 days after the concrete construc. tion but reconsideration is necessary for the application to high strength concrete because of the reduction in penetration of waterproof admixture. The results also show that the penetrat ive waterproof admixture has srrong resistance to the acid rain. However the waterproof capability of the admixture is not permanent especially under the natural exposure. Therefore the slab of a bridge should be paved with asphalt concrete. Other noticeable effects are the increase of heat and abrasion resistances from the use of the waterproof agents.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.10a
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• pp.87-94
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• 1994

During the construction of externally prestressed 7-span continuous segmental bridge, cracks beyond permissible limit were found at anchor zone of expansion joint segment. To eliminate this problem, tension side of diaphragm was prestressed by post-tensioning bars in vertical and horizontal direction. To investigate this remedy is acceptable, stresses of reinforcing bars and concrete surface were measured for the real structure in the field. The measurement was performed through each step of prestressing sequence during construction. Also to investigage stresses induced by live load, static load test was performed and the results was analyzed. In this paper it will be presented the procedure and results for this experimental study along with comparison with analytical study.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.182-187
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• 1993

Recent increasing traffic volumes have made many bridges on highway be widened. In widening of existing bridges, construction joints between old and new parts of concrete slabs are subjected to repeated traffic loads during placing and during of concrete. Therefore, the main goal of this paper is given to investigate the variation of the shear strength of widening deck. As a result, the occurrence of cracks in vibrating specimen is faster than that of non-vibrating one, and most of cracks are occurred at new concrete. And the difference of shear strength in vibrating specimen is larger than non-vibrating one, but the difference is negligible. Also, it shows the same result about direct and non-shrinkage joint specimen test.