• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.561-568
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• 2005

The object of this paper is to determine appropriateness for use of high-strength tensile bar as a tension web member. The gap K-joint of tensile bar types were compared with gap K-joint of square hollow section (SHS) types. For the same width-to-thickness ratio ($2{\gamma}=33.3$ ), tests were performed on four specimens of the SHS type and eight specimens of the tensile bar type. The comparison of capacity with the experimental results showed a capacity of the SHS type joint to be higher than that of the tensile bartype joint for the same brace-to-chord width ratio. Moreover, the capacity of the SHS type joints increased proportionally to the width ratio ${\beta}$), while tensile bar type joints increased as the tension width ratio (${\beta}2$). In failure mode, SHS-type specimens showed local buckling of the compression brace and plastic failure was observed between the tension brace and chord face, and with the tensile bar type specimens there appeared punching shear failure of the chord face at the toe of the connection plate. It is, therefore, concluded that width-to-thickness ratio should be lower than that of the hollow-section type and the relation between tension and compression width ratio should be considered.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.16-24
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• 2021

This experimental study was conducted to evaluate the in-plane and out-of-plane seismic performances of an unreinforced masonry walls (URMs) strengthened with prestressed steel-bar truss systems developed in the present investigation. The truss systems were installed on both faces of the walls. All the wall specimens were subjected to lateral in-plane or out-of-plane cyclic loads at the fixed gravity stress of 0.25 MPa. The seismic performance of the strengthened specimens was compared to that measured in the counterpart URM. When compared with the lateral load-displacement curve of the URM, the strengthened walls exhibited the following improvements: 190% for initial stiffness, 180% for peak strength, 610% for accumulated energy dissipation capacity, and 510% for equivalent damping ratio under the in-plane state; the corresponding improvements under the out-of-plane state were 230% for initial stiffness, 190% for peak strength, 240% for accumulated energy dissipation capacity, and 120% for equivalent damping ratio, respectively. These results indicate that the developed technique is very promising in enhancing the overall seismic performance of URM.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.1-9
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• 2020

In this study, a seismic reinforcement system was developed considering the rocking behavior of walls. The rocking behavior is to rotate left and right around the vertical axis of the wall, and the development system is a method of dissipating energy by installing a damper to a large displacement part. Developed steel rod damper was used, and steel rod diameter and length(aspect ratio) were selected as variables. As a result of the experiment, it was evaluated to have excellent seismic performance when the damper length was 260mm.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.259-270
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• 2007

This paper presents an analytical method of evaluating the flexural behavior of RC (reinforced concrete) beams strengthened with high-strengh bars. The former experimental results were used to compare with the analytical results. The experimental results also outline the advantages of externally strengtheng method with high-strenght bars. To evaluate the flexural behavior of RC beams strenghtend with unbonded high-strength bars, this paper proposes a method involving a simple strength-summation method. This method basically assumes that the total strength of RC beams strengthened with high-strength bars is equal to the sum of the strengths of the RC beams and the high-strength bars. This analytical method also includes the effects of compressive force due to the tension from high-strength bars. A comparison of the analytical and experimental results leads to the conclusion that the simple strength-summation mothod can simulate the flexural behavior of RC beams strengthened with high-strength bars with a good level of accuracy.

• Journal of the Korean GEO-environmental Society
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• v.25 no.4
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• pp.29-35
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• 2024

This is an analytical study to confirm the passive resistance effect before post-tensioning of steel bar anchors. When using a steel bar as a permanent anchor, if displacement occurs within the slope even before the head load is applied, the displacement is suppressed by the passive resistance caused by the interaction between the steel bar, grout, and surrounding soil. Accordingly, the shape of the failure surface and changes in the safety factor were examined using limit equilibrium analysis and finite element analysis targeting sites where steel bar anchors were actually applied. It was found that the safety factor of the slope reinforced with steel bar anchors is 2.02 using finite element analysis, which is about 5.9% smaller than 2.14 using limit equilibrium analysis. Also, the location of the failure surface was found to be deeper compared to the unreinforced slope. Likewise, the factor of safety has a 153% and 163% increase using finite element method and limit equilibrium analysis, respectively. In addition, the maximum displacement occurs in the lower unreinforced section within the slope, and the displacement is found to be reduced by 42 to 83% at the location where the steel bar anchors are installed.

• Journal of Biomedical Engineering Research
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• v.25 no.1
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• pp.71-76
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• 2004

In order to investigate the Post-operative changes in scoliotic spine according to selection of fusion level a mathematical finite element model of King-Moe type II scoliotics spine system was developed. By utilizing this finite element scoliosis model surgical correction simulation procedures of pedicle fixation and derotation were simulated. In consequence of the calculation by changing the fusion Levels, postoperative changes like Cobb angle, apical vertebrae axial rotation (AVAR), thoracic kyphosis, and rib hump were Qualitatively analyzed. In the analysis of operative kinematics, the decrease or Cobb angle was most prominent in distraction than in deroation. Applying the rod derotation only was not effective in decrease of Cobb angle but just caused increase of At AR and rib hump. From the operative simulation, co-action or distraction and translation during rod insertion has major impact on Cobb angle decrease and maintenance of kyphosis. With rod rotation, Cobb angle decrease was obtained, but combined increase of AVAR and rib hump was simulation observed as well. The case of most extended instrumentation range with 60o rod rotation produced double decrease of Cobb angle, but the increase of rib hump and AYAR occurred corresponding1y. The optimum selection of fusion level was proved as one level less than inflection position of the thoracic spine curvature.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.17-26
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• 2020

This study examined the structural effectiveness of the unbonded technique originally developed for seismic strengthening of unreinforced masonry walls on the basis of the prestressed steel bars and glass fiber (GF) grids. The masonry walls were strengthened by using individual steel bars or GF grids and their combination. Test results showed that the proposed technique was favorable in enhancing the strength, stiffness, and ductility of the masonry walls. When compared with the lateral load capacity, stiffness at the ascending branch of the lateral load-displacement curve, and energy dissipation capacity of the unstrengthened control wall, the increasing ratios were 110%, 120%, and 360%, respectively, for the walls strengthened with the individual GF grids, 140%, 130%, and 510%, respectively, for the walls strengthened with the individual steel bars, and 160%, 130%, and 840%, respectively, for the walls strengthened with the combination of steel bars and GF grids. The measured lateral load capacities of masonry walls strengthened with the developed technique were in relatively good agreement with the predictions by the equations proposed by Yang et al. Overall, the developed technique is quite promising in enhancing the seismic performance of unreinforced masonry walls.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.361-364
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• 2008

This study was performed to estimate the anchorage behavior for Bi Prestressed Concrete Girder(Bicon girder) which could introduce effectively prestressed forces into concrete girders. A bicon girder is manufactured by means of introducing pure bending moment that prestress simultaneously the compressive member(steel bar) and the tensile member(steel tendon). Therefore, the steel bar and the steel tendon must be unified in both ends and compressive and tensile force be offset. Anchorage dimension of 6 test specimens was designed under PTI specification which defined maximum stress and deformation to estimate structural behavior. Test results showed that the stress and the deformation of anchorage were within limits if the steel bar behaviored elastically.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.66-73
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• 2022

In this study, the experimental results of 7 dampers with the same strut height and similar cross-sectional area were compared based on the existing research results on steel dampers with rocking behavior. As steel plate dampers, SI-260, SV-260, SS-260 without Lateral deformation prevention detail(Ldpd), I-1, V-1, S-1 with Ldpd, and R20-260 with steel rod damper were evaluated. In addition, R15-260, which has a cross-sectional area of 0.56 times than other dampers, was also reviewed to appropriately evaluate the behavior of the steel rod damper. An important study result is the application superiority of the steel rod damper, which improved the unidirectional behavior of the steel plate dampers. This was proved in the moment-resistance capacity and displacement ratio evaluation. As a result of the evaluation, the R20-260, a steel bar damper, was evaluated as having the best performance. In addition, it is judged to have sufficient seismic resistance as it shows deformability up to a displacement ratio of 2.0.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3A
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• pp.383-390
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• 2008

A Precast Prefabricated Bridge Column using steel tube and prestressing bar was proposed for the application of precast method on substructure. A column specimen designed by the proposed bridge column system was made and performed a quasi-static test. The failure mode appeared to be a flexural failure and there is no damage on column segment connection. And it is good use of the self-centering ability by prestressing force. Test results showed that a column specimen satisfy the earthquake specification, and the structural stability was verified. Nonlinear finite element analysis was performed and compared with the test results. Force-displacement relation and location of crack from the analysis results were compared with the test results and it agreed well. The quantitative analysis was also performed by a parametric study using this modeling technique.