• Journal of the Korean Society of Radiology
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• v.10 no.5
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• pp.359-365
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• 2016

Fluoroscopy is performed when tissue or organ in the human body is examined, and it is used for diagnosis and procedure in back ailments. With regard to fluoroscopy equipment, distortion occurs on the peripheral part of fluoroscopic image rather than on its central part. This study measured distortion factors of vertical spacing ratio and distortion factor of diagonal spacing ratio before and after correction by applying a correction algorithm. According to measuring the vertical spacing ratio, post-correction standard deviation decreased by 0.04 in comparison with pre-correction one. Also measuring the diagonal spacing ratio, post-correction standard deviation decreased by 0.06 in comparison with pre-correction one. Consequently, the distortion of fluoroscopic image decreased after correction. A decrease in the distortion of image through the application of correction algorithm and the improvement of performance will be helpful in finding a correct position of lumbar puncture in nucleoplasty to treat lumbar disc herniation in the future.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.757-764
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• 2004

This paper deals with the numerical study on the displacement behavior of corner areas in an excavation site. Several corner areas always exist in the excavation site. The corner area has two free surfaces, which may become serious weak point from the viewpoint of structural stability. If the structural reinforcements are not applied adequately in corner areas, significant displacement of retaining wall could occur. What is worse, the collapse of retaining system rarely happens. In this paper, 3D numerical analyses were performed to investigate the effect of the arrangement of diagonal and normal strut. From the analysis results, it is found that the spacing between diagonal strut and normal strut should be less than 4m to avoid excessive displacement due to excavation.

• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.345-360
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• 2022

In this paper, the impact on seismic performance of an economical effective technique for retrofitting reinforced concrete (RC) columns using high-strength steel strips under high axial compression ratios was presented. The experimental program included a series of cyclic loading tests on one nonretrofitted control specimen and three retrofitted specimens. The effects of the axial compression ratio and spacing of the steel strips on the cyclic behavior of the specimens were studied. Based on the test results, the failure modes, hysteretic characteristics, strength and stiffness degradation, displacement ductility, and energy dissipation capacity of the specimens were analyzed in-depth. The analysis showed that the transverse confinement provided by the high-strength steel strips could effectively delay and restrain diagonal crack development and improve the failure mode, which was flexural-shear failure controlled by flexural failure with better ductility. The specimens retrofitted using high-strength steel strips showed more satisfactory seismic performance than the control specimen. The seismic performance and deformation capacity of the retrofitted RC columns increased with decreasing axial compression ratio and steel strip spacing. Based on the test results, a hysteretic model for RC columns that considers the transverse confinement of high-strength steel strips was then established. The hysteretic model showed good agreement with the experimental results, which verified the effectiveness of the proposed hysteretic model. Therefore, the aforementioned analysis can be used for the design of retrofitted RC columns.

• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.741-751
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• 2010

An experimental study was performed to investigate the earthquake resistance of the beam-column connections as a part of a precast concrete moment-resisting frame that uses precast concrete U-shaped shells for the beams. Five full-scale precast concrete specimens and one conventional monolithic concrete specimen were tested under cyclic loading. The parameters for this test were the reinforcement ratio, stirrup spacing, and end-strengthening details of the precast beam shell. The test results showed that regardless of the test parameters, the precast concrete beam-column connections showed good load-carrying capacity and deformation capacity, which were comparable to those of conventional monolithic concrete specimen. However, at large deformations, the beam-column connections of the precast concrete specimens were subjected to severe strength degradation due to diagonal shear cracks and the bond-slip of re-bars at the joint region. For this reason, the energy dissipation capacity and stiffness of the precast concrete specimens were significantly less than those of the cast-in-place specimen.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.83-90
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• 2007

The present study reports a simple unbonded-type shear strengthening technique for reinforced concrete beams using wire rope units. Fifteen beams failed in shear were repaired and strengthened with wire rope units, and then retested to failure. Influence of the prestressing force, orientation and spacing of wire rope units on the shear behavior of strengthened beams having shear span-to-depth ratios of 1.5, 2.5, or 3.25 were investigated. Test results showed that beams strengthened with wire rope units exhibited a higher shear strength and a larger post-failure deformation than the corresponding original beams. Inclined wire rope units was more effective for shear strength enhancement than vertical wire rope units. The increase of the prestressing force in wire rope units causes the decrease of the principal tensile stress in concrete, as a result, the diagonal tensile cracking strength of strengthened beams was higher than that of the corresponding original beams. Shear capacity of strengthened beams is compared with predictions obtained from ACI 318-05 and EC 2. Shear capacity of strengthened beams having shear span-to-depth ratio below 2.5 is reasonably predicted using ACI 318-05 formula. On the other hand, EC 2 overestimates the shear transfer capacity of wire rope units for beams having shear span-to-depth ratio above 2.5.