• Proceedings of the Korean Society of Laser Processing Conference
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• 2001.05a
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• pp.16-21
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• 2001

• Journal of the Korea Concrete Institute
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• v.26 no.6
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• pp.695-705
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• 2014

Precast concrete (PC) beam-column connections using ductile rods are proposed for earthquake zone. An existing beam-column connection, two PC specimens designed by considering failure modes and a conventional RC specimen were tested under cyclic loading to evaluate the seismic performance. The specimens were designed to satisfy the requirements of current design code. The variables are the yield strength of longitudinal reinforcing bars of PC beams. The test results showed that the proposed system applying smaller yield strength of the longitudinal reinforcing bars at the PC beams than the ductile rods was satisfied with seismic criteria. The deformation capacity and energy dissipation capacity of the proposed PC beam-column connections were greater than those of the existing DDC system.

• Journal of the Korean Geosynthetics Society
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• v.7 no.3
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• pp.41-49
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• 2008

This study was carried out the model experiment in laboratory to evaluate the bearing capacity improvement of soft ground as altered constraint condition of reinforcements according to geotextile, georid, steel bar. As a results, the value of BCR was increased linearly as improvement of the stiffness of reinforcements, and the factor governed the increasement of BCR was the increasement of frictions between reinforcement and clay as far as the constrain conditions increased until T=85.6kg. Moreover, An angle of inclination, ${\theta}$, between reinforcement and horizontal surface was distributed from $38^{\circ}$ to $50^{\circ}$ for Geotextile, from $45^{\circ}$ to $50^{\circ}$ for Geogrid and from $14^{\circ}$ to $16^{\circ}$ for steel bar. A radius of heaving, r, of clay ground by vertical weight at side was distributed from 0.6m to 0.7m for Geotextile, from 0.5m to 0.8m for Geogrid, and from 2.4m to 3.0m for steel bar. In case of steel bar, r was 4 times that of Geotextile.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.823-829
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• 2002

The composite frame system with reinforced concrete column and steel beam has some advantages in the structural efficiency by complementing the shortcomings between the two systems. The system, however has also a lot of problems in practical design and construction process due to the material dissimilarities. Considering these circumstances, this research is aimed at the development of the composite structural system which enables the steel beams to be connected to the R/C columns with higher structural safety and economy. Basically the proposed connection system is composed of four split tees, structural angles reinforced by stiffener, high strength steel rods, connecting plates and shear plates. The structural tests have been carried out to verify the moment transfer mechanism from beam flange to steel rods or connecting plates through the angle reinforced by siffener. The four prototype specimens have been tested until the flange of beam reached the plastic states. From the tests, no distinct material dissimilarities between concrete and steel have been detected and the stress transfer through wide flange beam - structural angle - high strength steel rod or connecting plate is very favorable.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.603-610
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• 2006

The external unbonded strengthening offers advantages in speed and simplicity of installation over other strengthening techniques. Unlike externally bonded steel plate or carbon fiber sheet, surface preparation of the concrete for installation of high-tension bar is not required and installation is not affected by environmental conditions. Anchoring pin or anchoring plate are installed at the end of beam to connect the high-tension bar to concrete beam. The deviator are used in order that supplementary external bars would follow the curvature of the tested beam. A set often laboratory tests on reinforced concrete beam strengthened using the technique are reported. The main test parameters are the section area of strengthening bar, the depth of deviator and the number of deviators. The paper provides a general description of structural behavior of beams strengthened using the technique. The test result of strengthened beam are compared with those from a reference specimen. It is shown that the reinforcing technique can provide greater strength enhancements to unstrengthened beam and that the provision of deviator enhances efficiency. The ultimate moment of specimen with two deviators was higher than that of specimens with one deviator. It is also shown that the external bars enhance strength of beams in shear.

• 한국방재학회:학술대회논문집
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• 2009.02b
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• pp.113.2-113.2
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• 2009

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.1
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• pp.3-10
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• 2018

This experimental investigation was conducted to observe the shear strengthening behavior of pre-damaged reinforced concrete (RC) beams strengthened with externally post-tensioning steel rods. A total of six simply supported beams - two control beams and four post-tensioned beams using external steel rods - were tested to failure in shear. The external steel rods of 18 mm or 28 mm diameter were respectively employed as post-tensioning material. The four post-tensioned beams have a V-shaped profile with a deviator (or saddle pin) located at mid-span, and the post-tensioning system increased the low load-carrying capacity and overcame a little bit of deflection caused by damage. Concretely, the load-carrying capacity and flexural stiffness were respectively increased by about 25~57% and 263~387% due to the post-tensioning when compared with the unstrengthened control beams.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.2
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• pp.11-17
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• 2018

Concrete is the well-used material in many architectural and civil structures. The behavior of concrete does exhibit a different characteristic in compression and tension, and it also shows an inelastic-nonlinear behavior. In addition, the concrete properties vary slightly depending on the environmental factor and manufacturer. These properties of concrete make the modeling or simulation of concrete material difficult. In reinforced concrete, particularly, there is a difficulty in bond-slip relationship between concrete and steel. However, in this paper, reserving remainder of these limits the finite element analysis for reinforced concrete beams through ABAQUS simulation has been carried out with some assumptions. Assumptions include the perfect bond of steel and concrete as well as the concrete damaged plasticity (CDP) in concrete property. There is a reasonable agreement between the experimental and numerical results, although the analytical strength and external rod deformation are slightly overestimated. The average and standard deviation between two results are 1.05 and 0.05, respectively. And the models and the computations lead to the evolution of fracture in bending beam.

• 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.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.453-463
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• 2012

Steel-concrete composite rigid-frame bridge is a type of integral bridge having advantages in bridge maintenance and structural efficiency from eliminating expansion joints and bridge supports, the main problems in bridge maintenance. The typical steel-concrete composite rigid-frame bridge has the girder-abutment connection where a part of its steel girder is embedded in abutment for integrity. However, the detail of typical girder-abutment connection is complex and increases the construction cost, especially when a part of steel girder is embedded. Recently, a new type of bridge was proposed to compensate for the disadvantages of complex details and cost increase. The compensation are expected to improve efficiency of construction by simplifying the construction detail of the girder-abutment connection. In this study, a static load test has been carried out to examine the behavior of the girder-abutment connection using real-scale specimens. The results of the test showed that the girder-abutment connection of proposed girder bridge has sufficient flexural capacity and rebars to control concrete crack should be placed on the top of abutment.