• Proceedings of the KSR Conference
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• 2008.11b
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• pp.864-869
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• 2008

Magnetic Levitated(Maglev) Vehicle, which utilizes electromagnetic forces between dual-pole electromagnets and a steel rail, generally runs on guideway structures. A prototype of an Urban Maglev Vehicle has been developed and tested in Korea, This study was conducted as a cooperation research subject of the 3-1 subject, performance improvement of maglev track structures, of the Center for Urban Maglev Program, statred in 2006. As the Maglev load is distributed rather than concentrated, a field test was conducted on Simple Span PSC-BOX Girder Bridge(L=25.0m) of the Expo-Maglev test track in Daejeon to examine the dynamic effect of the Maglev load on the bridge. Numerical analyses were also performed up to the maximum passing speed of 110 km/h by 10 km/h increments of Maglev Vehicle using Finite Element model of bridge, and girder deflections, accelerations and Dynamic Amplification Factor (DAF) are analysed.

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.13-22
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• 2000

In order to resolve the problem of increasing traffic entailed by the economic development, road system is reorganization and new highways are built, and long span bridges over 40m are being constructed in environmental and aesthetic considerations. Most long span bridges that are currently being constructed are in general steel box girder and preflex girder bridges; however these types of breiges are less efficiency than PSC I-type girder bridges in terms of construction cost and maintenance. Therefore, in these study, structural efficiency of PSC I-type girders based on section parameters, concrete compressive strength and other design parameter is observed to develope new PSC I-type girder for long span bridges. As a results of analysis, most important design parameters that control the stress of the girder are found to be the top flange width and the height of girder. In this light, the relationship between the two variables is determined and cross-section details of the girder that most appropriates for the long span bridges are proposed. The use of high strength concrete appears to increase the general design span however the increase rate of the span from increasing concrete ultimate strength appears to be reduced depending on the span. Also, the optimal girder spacing is determined through the parameter studies of design span using the proposed girder.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.433-442
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• 2013

This paper presents experimental research work for the evaluation of one-dimensional and two-dimensional acoustic source locations with 50m length of a precast prestressed concrete box girder. Acoustic events are generated by the impacts of Schmidt Hammer and the impact signals are detected by acoustic emission sensors mounted on the concrete web surface of PSC box girder with the average spacing of 9.34m. Based on the amplitude of detected acoustic signals, considering the noises developed in PSC box girder bridges, the arrival times of acoustic signals are estimated by the first arrival times of 0Volt, 0.5Volt, and 1.0Volt amplitude in each signal. Using Least Square Method, the velocities and the source locations of acoustic signals are evaluated. Based on the test results, the spacing of AE sensors and the AE sensor networks are discussed to reduce the source location errors.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.191-201
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• 2001

In spite of the increasing construction of segmental PSC box girder bridges, the techniques associated with real-time monitoring, construction control and safety assessment during construction have been less developed compared with the construction techniques. Thus, the development of an integrated system including real-time measurement and monitoring, control and safety assessment system during construction is necessary fur more safe and precise construction of the bridges. This study presents a prototype integrated monitoring system for preventing abnormal behavior and accidents under construction stages, that consist of behavior control system for precise construction, reliability-based safety assessment system, and structural analysis. Also, a prototype software system is developed on the basis of the proposed model. It is successfully applied to the Sea-Hae Grand Bridge built by FCM. The integrated system model and software system can be utilized for the safe and precise construction of segmental PSC bridges during construction.

• Journal of Korean Society of Steel Construction
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• v.18 no.2
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• pp.181-189
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• 2006

This study analyzes the effects of the curvature friction coefficient, the wobble friction coefficient, and the increased strength of concrete, reinforced tendon on optimum de signs by using the optimum-design program, to minimize the cost of a PSC box girder bridge using the full staging method. The objective of this study is to find a proper tendon for the friction coefficient, and thereafter, to indicate the direction of the study development about tendons and to indicate the direction of a study on the increased strength of used materials. This program used the SUMT procedure and Kavlie's extended-penalty function to allow infeasible design points in the process. Powel's direct method was used in searching design points, and the gradient approximate method was used to reduce the design hours.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.251-256
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• 1999

In the preliminary design stage of Prestressed Concrete (PSC) Box Girder Bridges, the design factors(including depth, thickness of web, and jacking force) decided by inexperience designer could heavily affect the final design factors. So there is a possibility that the design ends up with an excessively wasteful design. To aim at an economical design with preventing an excessive design, the optimal design program has been developed by using ADS optimal program and SPCFRAME(PSC Bridge analysis program) in these studies. The optimal design program automatically calculates economically optimized design studies. The optimal design program automatically calculates economically optimized design factors by introducing the optimal design techniques of PSC box girder bridge design. The objective function for optimal design is material cost of box girder and constrained functions are constituted with design specifications and workability. The optimal design techniques used the Sequential Unconstraint Minimization Technique (SUMT) with performing the optimal design program. In this study, We designed unprismatic section bridge and prismatic section bridge in the same design condition by optimal design program developed in this study. By analyzing the results we suggested the practical form of tendon's layout comparing the optimal desingns on the basis of each tendon's layout.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.54-60
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• 1998

PSC box bridges by MSS construction method in high-speed railway may not be cast in place at one step. Web and bottom flange(U member) in the cross section are cast in place at first, then top flange will be cast in place later with some time lag. In this section, stress distributions of U member and top flange are different with those in generally complete cast in place cross section. In the composite section composed of two different aged members, the redistribution of stresses takes place. This results from time-dependent strain characteristics of concrete and the effects of forces applied at the various stages. For comparison in the present paper, two models, one with the composite cross section and the other with generally complete cast in place cross section, are analyzed. The longitudinal stress differences of two models on considering construction stages are compared. As the analysis results show the considerable differences in the stresses of cross section between two models, the composition of cross section is considered for rational design of PSC box girder bridge.

• International Journal of Concrete Structures and Materials
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• v.10 no.sup3
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• pp.1-17
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• 2016

Recently, advanced transit systems are being constructed to reduce traffic congestions in metropolitan areas. For these projects, curved bridges with various curvatures are required. Many curved bridges in the past were constructed using aesthetically unpleasant straight beams with curved slabs or expensive curved steel box girders with curved slabs. Therefore, many recent studies have been performed to develop less expensive and very safe precast prestressed concrete (PSC) curved girder. One method of reducing the construction cost of a PSC curved girder is to use a reusable formwork that can easily be adjusted to change the curvature and length of a girder. A reusable and curvature/dimension adjustable formwork called Multi-tasking formwork is developed for constructing efficient precast PSC curved girders. With the Multi-tasking formwork, two 40 m precast PSC box girders with different curvatures were constructed to build a two-girder curved bridge for a static flexural test to evaluate its safety and serviceability performance. The static flexural test results showed that the initial cracking load was 1400 kN, exceeding the design cracking load of 450 kN. Also, the code allowed deflection of 50 mm occurred at a load of 1800 kN, verifying the safety and serviceability of the precast PSC curved bridge constructed using the multi-tasking formwork.

• Magazine of the Korea Concrete Institute
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• v.20 no.3
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• pp.34-39
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• 2008

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3A
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• pp.243-250
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• 2009

The purpose of this study is to investigate several strategies that can be used to extend the span of conventional PSC girder bridge and to propose a systematic procedure to evaluate the effect of each strategy on the span. In the preceding companion paper, fundamental equations were derived which constitute the assessment graphs and a possible domain for the design. Quantitative evaluation for extension of the span follows here by adopting a sample PSC girder bridge. It apparently shows a number of advantages of the proposed scheme in finding out why and how each strategy contributes to the span extension and in suggesting further improvement for a longer span. The results imply that increasing the strength of a girder, the multistage prestressing with the secondary tendons prestressed before composite action with a deck, and Decked PSC girder are very effective among the strategies examined. It is expected that the span of the PSC girder bridge can be well extended up to 50 m to 70 m which corresponds to a span of the conventional box girder bridges.