• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.93-104
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• 2008

study deals with the reliability assesment for the 5-year phases of a suspension bridge construction in Korea. The main objectives of this study are; (1) the evaluation of the reliability of a suspension bridge by considering an ultimate limit state for the fracture of main cable wires, (2) the determination of the critical phases among 28 construction stages for the deck erection, and (3) the evaluation of the reliability of the limit state for the erection control during construction stages. The research and the design of the suspension bridge have been focused on the state of construction mainly based on empirical data. Based on the recent survey of the distribution of accidents in Korean railways, over 80% of the accidents related to the uncertainties in human error, planning, design, materials and loads during construction have ben reported before the completion of construction. While many researches have evaluated the safety of bridges, the uncertainties in the construction phases have not been well treated in a guidelines or a specifications. An improved adaptive response surface method is used for the risk assessment in the construction phases of the target suspension bridge.

• Physical Therapy Rehabilitation Science
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• v.5 no.2
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• pp.70-77
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• 2016

Objective: The purpose of this study was to compare the activation of trunk and gluteal muscles during bridge exercises with a sling (BS), single-legged bridge exercise with a sling (SBS), single-legged bridge exercise (SB), and general bridge exercise (GB). Design: Cross-sectional study. Methods: Twenty-five healthy participants (19 males and 6 females, aged 27.8 [4.78]) voluntarily participated in this study. In the bridging exercise, each subject lifted their pelvis with their legs and feet in contact with the sling or normal surface. The electrical activities of the erector spinae (ES), gluteus maximus (GM), external oblique (EO), and internal oblique (IO) muscles during the bridging exercises on the 2 surfaces were measured using surface electromyography. Subjects practiced each of the four bridge condition three times in random order and average values were obtained. Results: On the ipsilateral side, activities of the IO, EO, and ES during SBS was significantly higher than those during BS, SB, and GB (p<0.05). Activities of the IO and EO during SB was significantly higher than those during BS and GB (p<0.05). On the contralateral side, activities of the GM and EO during SB and SBS was significantly higher than that during BS and GB (p<0.05). These results verify the theory that the use of sling and single leg lift increases the activation trunk and gluteal muscles during bridging exercises. Conclusions: The single-legged bridge exercise with a sling can be recommended as an effective method to facilitate trunk and gluteal muscle activities.

• Structural Monitoring and Maintenance
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• v.2 no.1
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• pp.19-34
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• 2015

One of the main causes of a limited use of nondestructive evaluation (NDE) technologies in bridge deck assessment is the speed of data collection and analysis. The paper describes development and implementation of the RABIT (Robotics Assisted Bridge Inspection Tool) for data collection using multiple NDE technologies. The system is designed to characterize three most common deterioration types in concrete bridge decks: rebar corrosion, delamination, and concrete degradation. It implements four NDE technologies: electrical resistivity (ER), impact echo (IE), ground-penetrating radar (GPR), and ultrasonic surface waves (USW) method. The technologies are used in a complementary way to enhance the interpretation. In addition, the system utilizes advanced vision to complement traditional visual inspection. Finally, the RABIT collects data at a significantly higher speed than it is done using traditional NDE equipment. The robotic system is complemented by an advanced data interpretation. The associated platform for the enhanced interpretation of condition assessment in concrete bridge decks utilizes data integration, fusion, and deterioration and defect visualization. This paper concentrates on the validation and field implementation of two NDE technologies. The first one is IE used in the delamination detection and characterization, while the second one is the USW method used in the assessment of concrete quality. The validation of performance of the two methods was conducted on a 9 m long and 3.6 m wide fabricated bridge structure with numerous artificial defects embedded in the deck.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.6
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• pp.1-8
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• 2006

The study is to analyze the surface luminance of the illuminated bridges according to the change of view point using luminance measurements with instrument CS-100 and ProMetric 1400. For the purpose the illuminated bridges of the structure type were sleceted. Also, the view points were classified the three types which are a perspective view, a building view, a driver view. The luminance of the surrounding sky, surface of river, upper structure or bridge, girder side, and pier or the objects was measured. As a result of this study, The Kwangjin and Dongho Bridge showed the luminance distribution of a perspective view was high. And the Olympic and Dongjac bridge the luminance distribution of building view was high. The luminance effect of the girder bridge that has no upper structure was distinguished for the perspective view, and the cable-stayed girder bridge and the arch bridge were characterized as the building view.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1697-1702
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• 2010

It has been recognized for decades that the spherical bearing which is sliding on curved surface in the intrinsic behavior is optimized for the railway bridge requiring a large slope deflection. However, the spherical bearing is easily corrosived at the PSC girder bridge which is exposed to the outside so the normal function of bridge bearing is not fulfilled fully. It is common that the corrosion is happened at the operating plate of steel bridge bearing and generally it is necessary to replace the bridge bearing after 20~25 years. Accordingly, It costs multi billion dollars for maintenance each year and the necessity of improvement become a issue. Korea Rail Network Authority(KR) suggested to apply the Elastomeric bearing instead of Spherical bearing through the task of construction site of 2006. But the normal Elastomeric bearing is optimized for the Highway bridge so it needs the special consideration to satisfy each design condition required by railway bridge. As the result of examination of Elastomeric bearing at the railway bridge construction site, the stress is decreased by effective dispersion of earthquakes and the maintenance fee is also decreased.

• International Journal of Highway Engineering
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• v.3 no.3 s.9
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• pp.135-146
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• 2001

This study focused on the investigation of compressive and flexural strengths development, and bond strength of latex modified concrete in order to validate the feasibility of application into concrete bridge deck overlay. Pull-out bond test was used for evaluating the bond strength of latex modified concrete to substrate. The main experimental variables were latex-cement ratio, surface preparation and moisture levels. The compressive strength of latex modified concrete decreased slightly and the flexural strength increased as the latex content increased from 5% to 20%. This might be due to the flexibility latex filled in voids and interconnections of hydrated cement and aggregates by a film of latex particles, respectively. In general, increasing the amount of latex will produce concrete with increased tensile and flexural strength and lower modulus of elasticity. Significant improvements in bond strength between new and existing concrete were achieved through the modification of the new concrete bridge deck overlay by latex polymers. The effect of surface preparation on bond of latex modified concrete to conventional concrete were significant at the conditions by sand paper and wire brush. A better bond could be achieved by rough surface rather than smooth. The saturated condition of surface is the most appropriate moisture level among the considered followed by dry condition and wet condition.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.721-726
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• 2002

The topic on today is dynamic response analysis of curved bridge-AGT(Automated Guide-way Transit) vehicle interaction system. Rubber wheel type AGT vehicle is adopted in this study, and the vehicle is idealized as three dimensional eleven DOF model. Three types of composited steel box girder bridges are modelized with F.E. method. And three types of artificially generated surface roughnesses are adopted for analysis. The dynamic equations of curved bridge, AGT vehicle and surface roughness are derived by using Lagrange's equation of motion. And the equations are solved by Newmark-${\beta}$ method. As a result, The dynamic increasement factor is inverse proportional to radius curvature.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.757-767
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• 2016

The power spectral density (PSD) for the road surface roughness on the bridges of minor roads in Wonju city and Hoengseong-gun, Gangwon-do is presented. To obtain the PSD, the road surface roughness on 18 different bridges with various superstructure type and span is measured by GPS at every 10 to 30cm interval. Assuming the PSD as the stationary normal probability process with zero mean value, the PSD of measured road surface roughness is obtained by applying the Maximum Entropy Method (MEM). A simple formula in evaluating the PSD of RC slab bridge, Rahmen bridge and PSC I-girder bridge which is applicable to the dynamic response analysis of bridges considering the road surface roughness is proposed. Using the calculated PSD curves, the road surface conditions on the 18 bridges are evaluated. The statistical relationship between the PSD and the IRI is presented by applying linear regression and correlation analysis.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.125-132
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• 1998

In this study the fire, due to overturning of oil tanker on the bridge induced heat transfer analysis and thermal stress analysis are carried out. The results of analysis for fire history of 1 hour present very large thermal gradient near the surface. However, the temperature increase of tendon & rebar that is the main resistant member of bridge is not sufficient to change material properties. The Von-Mises yield criteria is used to calculate the depth of delamination, The depth of delamination is about 4cm at center of fire and this value is close to measured value.

• Korean Journal of Environmental Biology
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• v.23 no.2 s.58
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• pp.93-97
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• 2005

Zooplankton dynamics were investigated based on samples collected monthly during the period between November 1998 and October 1999 at 15 stations in Gwangyang and Sachon Bay. Zooplankters were quantitatively collected with horizontal towing through the surface and oblique hauling from the bottom to surface at each station, simultaneously. A total of 88 taxa of zooplankton were distributed and 60 taxa were identified to species. Copepods showed the prosperity in species number of 52 species. Number of taxa occurred in samples hauled obliquely always showed $2\~5$ more species than those captured in the surface except for stations near the Namhae bridge. In waters near Namhae bridge, fast current seemed to mix waters vertically. Seasonally these differences were more distinct in the spring and summer than those in other seasons possibly due to the stratification in warmer seasons. In quantitative aspects, differences between two layers seemed to be obscure. Spatial and temporal variations in species diversity of copepods showed more prosperity in pelagic realm than those in the surface. Our collection carrying out in day time might be one of the important reason to cause these differences in zooplankton dynamics between two layers.