• Proceedings of KOSOMES biannual meeting
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• 2008.05a
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• pp.61-67
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• 2008

This study analyzes the characteristics of material transportation between Busan new-port and Nakdong river estuary. Measurements of water temperate, salinity, turbidity, and tide is also analyzed to determine the characteristics of sea water and described the tidal current between two regions. For the purpose of indicating characteristics of tidal current numerical modeling is used. From the observed results, the total volume transport of sea water calculations revealed $184.71m^3/sec$ and residual volume transport was $(+)59.74m^3/sec$ during the 1st field measurement, and the total volume transport was $331.15m^3/sec$ and residual volume transport was $(-)28.88m^3/sec$ during the 2nd. The numerical simulation for three different topography cases are calculated. The results are summarized as follows: 1) The volume of material transportation about $0.7\sim18.4%$ is decreased as the depth of Busan new-port decrease (10 m). 2) The volume of material transportation about $3.5\sim21.9%$ is increased, as channel(water depth is 5 m) constructed to the Nakdong river estuary direction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.3
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• pp.12-20
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• 2023

This study presents basic data on how to secure stability by analyzing the change in tensile force of steel rod and the inclination characteristics of PSC BOX in the "Temporary fixation system using internal prestressing tendon", which is mainly applied to construction of superstructures by FCM. To date, it has been difficult to confirm the changes in tension force of the steel rod and the inclination of the PSC BOX because the steel rod was installed vertically inside the pier and the PSC BOX. Therefore, measurement of the change in length of the steel rod and the displacement of PSC BOX were performed using a micro-measured FBG sensor. Comparisons of the calculated tensile force and the residual tensile force of the steel rod revealed that the safety factor decreased in all bridges. The cause was mainly identified to be the loss of tensile force in fixation~1segment, and countermeasures are suggested. The analysis of the inclination characteristics showed that the inclination increased with the segment progresses even in bridges with sufficient safety factor, and the difference before and after the segment was confirmed. In addition, the increase in inclination was related to the loss of tension force in the steel rod, and the stress on the opposite sides of the inclination was further reduced. It is believed that upward tensile force is generated in the steel rod on the opposite side of the inclined side due to the unbalanced moment, causing the difference in stress of the steel rod between the two sides.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.513-523
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• 2010

For continuous I-girder bridges, a large negative bending moment is generated near pier region so that plastic hinge is first formed at this point. Then, the bending moment is redistributed when the I-girder has enough flexural ductility (or rotational capacity). However, for I-girder with high strength steel, it is known that the flexural ductility is considerably decreased by increasing the yield strength of material. Thus, it is necessary to conduct a study for guaranteeing proper flexural ductility of I-girder with high-strength steel. In this study, the evaluation of flexural ductility of negative moment region of I-girder with high strength steel where yield stress of steel is 680 MPa is presented based on the results of finite element analysis and experiment. From the results, it is found that the flexural ductility of the I-girder is significantly reduced due to the increase of elastic deformation and the decrease of plastic deformation ability of the material when the yield strength increases. In this study, the method to improve the flexural ductility of I-girder with high strength steel is proposed by an unequal installation of cross beam and an optimal position of cross beam is also suggested. Finally, the effects of the unequal installation of cross beam on the flexural ductility are discussed based on the experimental results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.3
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• pp.21-29
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• 2023

In this study, the stress characteristics of temporary fixed steel rods were analyzed in the "temporary fixing system using internal prestressing tension", which is mainly applied to the construction of superstructures by FCM. It was difficult to confirm the changes in initial tensile force in this system because the steel rod was internally connected to the pier and the PSC BOX. Therefore, measurement was performed before and after the completion of each segment using an FBG sensor to measure the change in the micro length of the steel rod. The results of the analysis showed that 75% to 90% of the maximum vertical contraction of the steel rod that occurred until the completion of the cantilever segment occurred in the fixing ~ 1segment, and the maximum loss of initial prestressing force was 39%. Such excessive loss of tension force to 1 segment means that tension is needed to improve the precision of construction during the fixation, and re-tension is needed to secure stability for conduction of cantilever segments after the completion of 1segment. In the 2 ~ last segment, the stress of the steel rod decreased gradually, and in the summer, the decrease in stress tended to partially recover due to the increase in the length of the steel rod corresponding to the increase in the vertical volume of PSC BOX. The dominant factor in the stress change in 2~ last segment in this phenomenon is judged to be the change in the length of the steel rod according to the temperature. Unlike the change in length, the relaxation was 1.2-2.7%, which was mostly offset by the opposite stress corresponding to the temperature stress. Therefore, a plan was proposed to improve the internal stress, such as adjusting the fixation time.