• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.137-146
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• 2005

This study presents the shape iteration method and the updated Lagrangian methods to calculate the initial tension and the reference length of cables of cable-stayed bridges. The girders and towers of cable-stayed bridge are modelled as 3-dimensional frame elements and the cable as nonlinear truss element or Ernst's cable element. Compared with the initial tensions of cables by finite element method in this study and by trial-and error method in practices, the tensions by the former are shown to be a little less than the those by the latter. The reference lengths of cables by Ernst's cable elements are almost consistent with those of cables by nonlinear truss elements. And the reference length of cables in this study are almost consistent with the arc length of beam with the same initial tension. Therefore the reference lengths of cables in cable-stayed bridges are shown to be obtained simply by the theory of beam with the initial tension calculated in this study.

• Journal of the Korean Society for Railway
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• v.16 no.5
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• pp.394-401
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• 2013

Here we report the results of an experimental laboratory test to verify the applicability to railway bridges of a PSC I girder of which the upper flange thickness was increased to improve sectional performance. The thicker this flange is, the further upward the neutral axis is moved. If in this way the span length can be increased to 40m long, the bridge may be constructed with four girders instead of five. Therefore, construction cost could be lowered by reducing the weight of the long span structure due to increased sectional efficiency. It was also necessary to be certain that the dynamic performance of this relatively flexible structure would be applicable to railway bridges. Therefore numerical analysis, as well as static and dynamic tests, was carried out for a full-size PSC I girder. Based on these results, it was verified that the performance of the PSC I railway bridge satisfied the performance criteria of the design code.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.9
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• pp.776-787
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• 2002

Automation of welding process in shipyards is ultimately necessary, since the welding site is spatially enclosed by floors and girders, and therefore welding operators are exposed to hostile working conditions. To solve this problem, a welding mobile robot that can navigate autonomously within the enclosure has been developed. To achieve the welding task in the closed space, the robotic welding system needs a sensor system for the working environment recognition and the weld seam tracking, and a specially designed environment recognition strategy. In this paper, a three-dimensional laser vision system is developed based on the optical triangulation technology in order to provide robots with 3D work environmental map. Using this sensor system, a spatial filter based on neural network technology is designed for extracting the center of laser stripe, and evaluated in various situations. An environment modeling algorithm structure is proposed and tested, which is composed of the laser scanning module for 3D voxel modeling and the plane reconstruction module for mobile robot localization. Finally, an environmental recognition strategy for welding mobile robot is developed in order to recognize the work environments efficiently. The design of the sensor system, the algorithm for sensing the partially structured environment with plane segments, and the recognition strategy and tactics for sensing the work environment are described and discussed with a series of experiments in detail.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.283-293
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• 2006

Recently, various types of structural systems for skyscrapers are studied as the height and size of the building structures rapidly increase due to social and economical needs. The mega frame system among them, which is the structural system developed recently, is known as a suitable structural system for skyscrapers because this structural system has sufficient stiffness against the lateral forces by combination of mega members which consist of many columns and girders. Since the mega frame structure has significant numbers of elements and nodes, it takes tremendous times and computer memories to analyze and design the structures. Therefore, the exclusive structural analysis program for mega frame system is developed to reduce the efforts and time required for the analysis and design of mega frame structure. To this end, an efficient modelling technique using the characteristics of mega frame structures and an efficient analytical model, which uses a few DOFs selected by the user using the matrix condensation method, are developed in this study. Static and dynamic analyses are conducted using an example structure. The effectiveness and accuracy of the developed program we verified by the comparison between the results of the proposed method and the conventional method.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.5 s.51
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• pp.11-23
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• 2006

This paper evaluates the seismic response of multi-span prestressed concrete girder bridges typically found in the New Madrid Seismic Zone region of the central United States. Using detailed nonlinear analytical models and synthetic ground motion records for Memphis, TN, nonlinear response history analyses are performed for two levels of ground motion: 10% probability of exceedance (PE) in 50 years, and 2% probability of exceedance (PE) in 50 years. The results show that the bridge performance is very good fur the 10% PE in 50 years ground motion level. However, the performance for the 2% PE in 50 years ground motion is not so good because it results in highly inelastic behavior of the bridge. Impact between decks results in large ductility demands on the columns, and failure of the bearings that support the girders. It is found that making the superstructure continuous, which is commonly performed for reducing dead load moments and maintenance requirements, results in significant improvement in the seismic response of prestressed concrete girder bridges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.1
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• pp.69-76
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• 2020

Bridges which are components of road network consume large amounts of resources such as concrete and steel materials, which have large environmental impacts during construction. This causes a great environmental burden. In order to reduce the environmental impact caused by the construction of the bridge, the environmental impact should be reviewed based on reasonable data in the early design stage. The purpose of this study is to provide basic data for LCA-based environmental impact assessment in the process of selecting bridge type in the early design stage. For this purpose, design data for four types of PSC bridges (general PSC girder, IPC girder, e-Beam, DR girder) were collected and LCA was performed to analyze the basic unit value and impact factors of environmental load. The results of the analysis showed that the environmental impact of IPC girder was the smallest, and the environmental impact of e-Beam was 133.7% higher than that of IPC girder. In addition, concrete, reinforcement, PC strand, square timber, sheath pipe, and steel plate were derived as the main factors that generate 98.5% of the overall environmental impact of PSC girder.

• Computers and Concrete
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• v.19 no.6
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• pp.725-736
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• 2017

This paper presents the two-, three-, and four-lane transverse reduction factor based on FEA method, probability theory, and the recently actual traffic flow data. A total of 72 composite girder bridges with various spans, number of lanes, loading mode, and bridge type are analyzed with time-varying static load FEA method by ANSYS, and the probability models of vehicle load effects at arbitrary-time point are developed. Based on these probability models, in accordance to the principle of the same exceeding probability, the multi-lane transverse reduction factor of these composite girder bridges and the relationship between the multi-lane transverse reduction factor and the span of bridge are determined. Finally, the multi-lane transverse reduction factor obtained is compared with those from AASHTO LRFD, BS5400, JTG D60 or Eurocode. The results show that the vehicle load effect at arbitrary-time point follows lognormal distribution. The two-, three-, and four-lane transverse reduction factors calculated by using FEA method and probability respectively range between 0.781 and 1.027, 0.616 and 0.795, 0.468 and 0.645. Furthermore, a correlation between the FEA and AASHTO LRFD, BS5400, JTG D60 or Eurocode transverse reduction factors is made for composite girder bridges. For the two-, three-, and four-lane bridge cases, the Eurocode code underestimated the FEA transverse reduction factors by 27%, 25% and 13%, respectively. This underestimation is more pronounced in short-span bridges. The AASHTO LRFD, BS5400 and JTG D60 codes overestimated the FEA transverse reduction factors. The FEA results highlight the importance of considering span length in determining the multi-lane transverse reduction factors when designing two-lane or more composite girder bridges. This paper will assist bridge engineers in quantifying the adjustment factors used in analyzing and designing multi-lane composite girder bridges.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.169-176
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• 2006

Prestressed composite girder with concrete infilled steel tubes(PSC-CFT girder) is new type of bridge girder which enhances the resisting capacities due to the double composite action of PSC composite girder and concrete infilled tube. The flexural behaviors of PSC-CFT girder in the negative moment regions are investigated based on the experimental observations recently performed on two of 3.6m long specimens. The mechanical and structural roles and failure mechanism of the composite action are discussed through comparing the test results with those numerically predicted by the three methods of one and three-dimensional nonlinear finite element analysis, and section analysis method.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.167-175
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• 1999

Many composite girder bridges have been constructed for about thirty five years. Nowadays they are aged or deteriorated because of the increase in traffic and vehicle loads. In this study, the effect of strengthening with glass fiber sheet is investigated to estimate the possibility for applying to damaged prestressed concrete bridges. One normal and eight cracked specimens which had been preloaded were tested. The cracked specimens were strengthened with either external prestressing or bonding glass fiber sheet, or using both methods. The results showed that the maximum loads are almost same for both methods. So it seems that the strengthening with glass fiber sheet can be used for strengthening damaged prestressed concrete girders. It is important that proper devices should be selected to prevent glass fiber sheet from premature bonding failure below its maximum load, which is similar to end anchorage problem in external prestressing method. It is proved that the devices proposed in this paper have sufficient anchoring capability to increase load carrying capacity.

• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.109-116
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• 2014

The flexural behavior test of UHPC segmental box girder which has 160 MPa compressive strength and 15.4 m length was carried out. The effect of steel fibers in combination with reinforcing bars on improving the ductile performance of UHPC box girder was evaluated by comparing the flexural behavior of the UHPC segmental box girders made by the two kinds of mixing portion. The test variables are volume fraction of steel fibers and the arrangement of reinforcing bars. The behavior of UHPC box girder BF2 composed of 1% volume fraction of steel fibers and longitudinal reinforcing bars in web and upper flange with stirrup showed the similar ductile behavior with the girder BF1 composed of 2% volume fraction without stirrup in elastic stress region. But BF1 had the better stiffness and showed the more ductile behavior in inelastic stress region. Segmental interfaces of UHPC box girder have not any crack and slide until the final flexural collapse load.