• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.609-614
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• 1997

Recently, many researchers have performed R&D about strengthening of R/C with steel plates, carbon fiber sheets. aramid fiber sheets and glass fiber sheets, and so on. However most of research were limited in study of flexural strengthening of R/C beams. This paper shows the results of an experimental study on shear reinforcement of deep beams using Glass Fiber Sheet in relation to shear-span ratio. strengthening orientation and anchorage. The results prove that shear failure is governed by reinforced orientation. adherence and anchorage. Additional anchorage of fibers does not only cause the improvement in the internal resistance, but also control the brittle shear failure of specimen after reaching the maximum load.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.327-330
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• 2005

Bond failure of reinforcing bar generally take place by splitting of the concrete cover as bond force between concrete and reinforcing bars exceeds the confinement of the concrete cover and reinforcement. However, the confinement force in practice has a limitation. Thus, the only variable is the bearing area corresponding to the change of bond force. In this study, to the evaluate anchorage strength of high relative rib area bars, hook bond test specimens are tested and the results are discussed. Higher rib height bars when bars are confined showed higher anchorage strength than lower rib higher bars.

• Structural Engineering and Mechanics
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• v.41 no.3
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• pp.407-420
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• 2012

This study investigated possible ways to replace conventional stirrups used on high-strength concrete members with improved reinforcing materials. Headed bar and high-strength steel were chosen to substitute for conventional stirrups, and an experimental comparison between the shear behavior of high-strength concrete large beams reinforced with conventional stirrups and the chosen stirrup substitutes was made. Test results indicated that the headed bar and the high-strength steel led to a significant reserve of shear strength and a good redistribution of shear between stirrups after shear cracking. This is due to the headed bar providing excellent end anchorage and the high-strength steel successfully resisting higher and sudden shear transmission from the concrete to the shear reinforcement. Experimental results presented in this paper were also compared with various prediction models for shear strength of concrete members.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.12
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• pp.21-26
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• 2018

For evaluating equations of bursting force in different codes, comparative study of the formulas was conducted. Because the equations does not consider variables such as shape of anchorages and duct, a relation between the bursting forces and the variables has to be analyzed. In this paper, the bursting forces equation was proposed by finite element analysis. As evaluation through comparison of the proposed equation with the previous ones and an experiment, it was figured out that bursting force computed by the proposed equation could be used for design of reinforcement in the anchorage zone.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.2
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• pp.51-58
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• 2022

Flat plate slab is cost-efficient structural system widely used in high rise building, apartment and parking garages. But flat plate-column connections are so weak against punching shear failure that it may cause collapse of overall structure. In this study, spiral type shear reinforcement which increases the shear strength and ductility of the plate-column connection and has good workability was proposed. And experimental test was performed to verify the punching shear capacity of spiral type shear reinforcement. The current code does not accurately estimate the punching shear strength of slab-column connection with shear reinforcement because slab is so slender that punching failure may occurred before shear reinforcement reached yield stress. Therefore modified equation of ACI code for punching shear strength was proposed base on finite element analysis using LUSAS program, and data analysis from CEB-FIP database.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.493-494
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• 2009

Two strengthened columns and an unstrengthened control column were tested to failure under cyclic lateral load combined with a constant axial load to effect of anchorage of T-shaped steel plate in the strengthened column using wire rope units. Main variables considered were anchorage method of T-shaped steel plate. Tested columns were compared with those of conventionally tied columns tested by research of before. Test results showed that lateral load capacity and the displacement ductility ratio of anchorage of T-shaped steel plate in the strengthened column increased 40% and 130% than unstrengthened column, respectively. In particular, at the same effective lateral reinforcement index, a much ductility ratio was observed in the strengthened columns than in the tied columns.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.667-675
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• 2012

Flat plate are being used more in buildings requiring a high level of technical installations or in buildings needing changeable room arrangements during their life time such as office buildings. The main problem in flat plate is its weak resistance against a punching failure at its slab-column connections. Therefore, in this research, an experimental study on full-scale interior slab-column connection was performed. Three types of shear reinforcements were tested to prevent brittle punching shear failure that could lead to collapse of the structure. A series of four flat plate specimens including a specimen without shear reinforcement and three specimens with shear reinforcements were tested. The slabs were tested up to failure using monotonic vertical shear loading. The presences of the shear reinforcements substantially increased punching shear capacity and ductility of the interior slabcolumn connections. The test results showed that a slab that did not have enough bond length failed before shear reinforcement yielded due to anchorage slip. Also, FEM analyses were performed to study an effect of slab thickness and concrete compressive strength on the flat plate slab. The analytical study results were used to propose a method to calculate performance capacity of shear reinforcement in slab-column connection.

• The korean journal of orthodontics
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• v.44 no.2
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• pp.88-95
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• 2014

Objective: The purpose of this study was to compare the treatment duration and dentoskeletal changes between two different anchorage systems used to treat maxillary dentoalveolar protrusion and to examine the effectiveness of en-masse retraction using two miniscrews placed in the midpalatal suture. Methods: Fifty-seven patients (9 men, 48 women), who had undergone level anchorage system treatment at Aichi-Gakuin University Dental Hospital (Nagoya, Japan) were divided into two groups according to the method of maxillary posterior anchorage reinforcement: midpalatal miniscrews (25 patients, mean age 22 years) and conventional anchorage (32 patients, mean age 19 years). The en-masse retraction period, overall treatment duration, pre-treatment effective ANB angle, and change in the effective ANB angle were compared with an independent-samples t -test. Results: Compared to the headgear group, the duration of en-masse retraction was longer by approximately 4 months in the miniscrew group (p < 0.001). However, we found no significant difference in the total treatment duration between the groups. Moreover, a greater change in the effective ANB angle was observed in patients treated with miniscrews than in those treated with the conventional method (p < 0.05). Conclusions: The level anchorage system treatment using miniscrews placed in the midpalatal area will allow orthodontists more time to control the anterior teeth during en-masse retraction, without increasing the total treatment duration. Furthermore, it achieves better dentoskeletal control than does the conventional anchorage method, thereby improving the quality of the treatment results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.3
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• pp.188-193
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• 1998

An experimental study was performed on the pull-out behavior of 90-deg standard hooks from exterior beam-column connections. The effects of lateral confinement and fiber reinforcement of joint area were investigated. It was concluded ; (1) Substitution of the transverse column (confining) reinforcement with steel fibers at the joint region effectively reduces the extent of cracking in exterior joints caused by pull-out of hooked bars; and (2) The strength and ductility of hooked bars under pull-out forces are positively influenced by substituting the conventional confining reinforcement of exterior joints with steel fibers. Application of steel fibers to exterior joints seems to be an effective technique for improving the anchorage conditions of hooked bars, and also for reducing the congestion of reinforcement in exterior beam-column connections.

• International Journal of Concrete Structures and Materials
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• v.9 no.4
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• pp.415-425
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• 2015

Reinforced concrete beams with insufficient shear reinforcement were strengthened using glass fiber reinforced polymer (GFRP) plates. In the study, the effect of the number of bolts on the load capacity, energy dissipation, and stiffness of reinforced concrete beams were investigated by using anchor bolt of different numbers. Three strengthened with GFRP specimens, one flexural reference specimen designed in accordance to Regulation on Buildings Constructed in Disaster Areas rules, and one shear reinforcement insufficient reference specimen was tested. Anchorage was made on the surfaces of the beams in strengthened specimens using 2, 3 and 4 bolts respectively. All beams were tested under monotonic loads. Results obtained from the tests of strengthened concrete beams were compared with the result of good flexural reference specimen. The beam in which 4 bolts were used in adhering GFRP plates on beam surfaces carried approximately equal loads with the beam named as a flexural reference. The amount of energy dissipated by strengthened DE5 specimen was 96 % of the amount of energy dissipated by DE1 reference specimen. Strengthened DE5 specimen initial stiffness equal to DE1 reference specimen initial stiffness, but strengthened DE5 specimen yield stiffness about 4 % lower than DE1 reference specimen yield stiffness. Also, DE5 specimen exhibited ductile behavior and was fractured due to bending fracture. Upon the increase of the number of anchorages used in a strengthening collapsing manner of test specimens changed and load capacity and ductility thereof increased.