• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.11 no.3
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• pp.31-51
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• 1982

For studying this project, we selected a 2-storied detached house as a sample which was constructed in July 1976, the last year of the 3rd 5-years economic and social development plan and also the middle year between the years of the 1st oil crisis and the 2nd oil crisis, located In Gayang-dong, Daejeon City. The contents and scope of this project was to produce retrofit measures by theoretically analyzing the building energy use between both of pre-retrofit and post-retrofit conditions of this sample house, and to compare and analyze the predicated data with experimented data under post - retrofit condition. It is suggested in this report that we have to develop rational and practical retrofit measures for energy conservations in existing residences.

• Structural Engineering and Mechanics
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• v.73 no.3
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• pp.239-257
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• 2020

In the present study, an innovative steel bracket and haunch hybrid scheme is devised, for retrofitting of earthquake damaged deficient beam-column sub-assemblages. Formulations are presented for evaluating haunch force factor under combined load case of lateral and gravity loads for the design of double haunch retrofit. The strength hierarchies of control and retrofitted beam-column sub-assemblages are established to showcase the efficacy of the retrofit in reversing the undesirable strength hierarchy. Further, the efficacy of the proposed retrofit scheme is demonstrated through experimental investigations carried out on gravity load designed (GLD), non-ductile and ductile detailed beam-column sub-assemblages which were damaged under reverse cyclic loading. The maximum load carried by repaired and retrofitted GLD specimen in positive and negative cycle is 12% and 28% respectively higher than that of the control GLD specimen. Further, the retrofitted GLD specimen sustained load up to drift ratio of 5.88% compared with 2.94% drift sustained by control GLD specimen. Repaired and retrofitted non-ductile specimen, could attain the displacement ductility of three during positive cycle of loading and showed improved ductility well above the expected displacement ductility of three during negative cycle. The hybrid haunch retrofit restored the load carrying capacity of damaged ductile specimen to the original level of control specimen and improved the ductility closer to the expected displacement ductility of five. The total cumulative energy dissipated by repaired and retrofitted GLD, non-ductile and ductile specimens are respectively 6.5 times, 2.31 times, 1.21 times that of the corresponding undamaged control specimens. Further, the damage indices of the repaired and retrofitted specimens are found to be lower than that of the corresponding control specimens. The novel and innovative steel bracket and haunch hybrid retrofit scheme proposed in the present study demonstrated its effectiveness by attaining the required displacement ductility and load carrying capacity and would be an excellent candidate for post-earthquake retrofit of damaged existing RC structures designed according to different design evolutions.

• Structural Engineering and Mechanics
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• v.27 no.4
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• pp.393-408
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• 2007

This paper presents the findings of an experimental study to evaluate retrofit methods which address particular weaknesses that are often found in reinforced concrete structures, especially older structures, namely the lack of the required flexural and shear reinforcement within the columns and the lack of the required shear reinforcement within the joints. Thus, the use of a high-strength fiber jacket for cases of post-earthquake and pre-earthquake retrofitting of columns and beam-column joints was investigated experimentally. In this paper, the effectiveness of the two jacket styles was also compared.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.3
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• pp.133-141
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• 2013

This paper presents the seismic evaluation and prediction of a damaged piloti-type Reinforced Concrete (RC) building before and after post-retrofitting under successive earthquakes. For considering realistic successive earthquakes, the past records measured at the same station were combined. In this study, the damaged RC building due to the first earthquake was retrofitted with a buckling-restrained brace (BRB) before the second earthquake occurred. Nonlinear Time History Analysis (NTHA) was performed under the scaled intensity of the successive ground motions. Based on the extensive structural response data obtained form from the NTHA, the fragility relationships between the ground shaking intensity and the probability of reaching a pre-determined limit state was were derived. In addition, The the fragility curves of the pre-damaged building without and with the BRBs were employed to evaluate the effect of the successive earthquakes and the post-retrofit effect. Through the seismic assessment subjected to the successive records, it was observed that the seismic performance of the pre-damaged building was significantly affected by the severity of the damage from the first earthquake damages and the hysteresis behavior of the retrofit element.

• Journal of the Korean Society of Safety
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• v.17 no.2
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• pp.85-91
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• 2002

A research on the performance of retrofit anchors was conducted using adhesives for rehabilitation. From the pull-out tests of the chemical anchors, the effect of the hole diameter, spacer, temperature, moisture, embedment depth, and aging time were investigated. The spacer did not directly increased the pull-out load hilt increased post-yielding resistance therefore the ductility of the retrofit anchors. When the hole was cleaned and dried after the immersion, the pull-out load was greatly increased compared to the wet hole. A design equation was unposed depending on the embedment depth of the anchor bolt.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.3
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• pp.293-300
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• 2015

In this study, a series of forced vibration testing and ambient vibration measurement were performed at a lowrise masonry-infilled reinforced concrete frame structure before and after seismic retrofit and its dynamic properties were extracted using system identification techniques. Also, analytical models which show similar dynamic properties to the measures ones were constructed. The system identification results showed that damping ratios in x direction along which the dampers were installed has been increased. From the comparison between the analytical models, the effective stiffness of post-installed member and post-reinforced members(shear walls and damper frames) were only 50% of gross sectional stiffness of the members, which indicates that the these members were not fully integrated with the existing structure or members. In addition, support condition of post-installed footing has to be pinned in y direction to match the dynamic properties, which is seemingly caused by the change of fixity of the soil due to the installation of new footing.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.571-578
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• 2003

An effective seismic retrofit scheme for inverted V braced (or chevron type) steel frames was proposed by studying the redistribution of forces in the post-buckling range. The steel frames with chevron bracing are highly prone to soft story response once the compression brace buckles under earthquake loading. This paper shows that the seismic performance of such frames could be significantly improved by supplying tie bars to redistribute the inelastic deformation demand over the height of the building. A practical design method of the retrofit tie bars was also proposed by considering the sequence of buckling occurrence.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.157-163
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• 2003

Recently, the number of Prestressed Concrete(PSC) bridges needed repair and retrofit because of the increase of heavy traffic loads and aging of concrete materials. But there are a few related researches about strengthening PSC bridges. In this study, the practicability of strengthening methods for PSC beam were studied by the static experimental method. PSC beams in length of 6m were made with concrete slabs. Glass fiber sheeting and external post-tensioning methods were used for strengthening PSC beams. Some beams were strengthened after cracks to investigate the applicability for cracked bridges. As a result, there strengthening methods were efficient at increasing the cracking loads and the failure load, to decrease deflection and prevent cracks. In the case of using glass fiber retrofit methods, it should be careful in the anchorage problems for preventing the bonding failure.

• Steel and Composite Structures
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• v.52 no.5
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• pp.543-555
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• 2024

This study examines the seismic vulnerability of vertically irregular reinforced concrete (RC) frame buildings, focusing on the effectiveness of retrofitting techniques such as rocking walls (RWs) in mitigating soft story mechanisms. Utilizing a seven-story residential apartment as a prototype in a high-seismicity urban area, this research performs detailed nonlinear simulations to evaluate both regular and irregular structures, both before and after retrofitting. Pushover and nonlinear time history analyses were conducted using OpenSees software, with a suite of nine ground motion records to capture diverse seismic scenarios. The findings indicate that retrofitting with RWs significantly improves seismic performance: for instance, roof displacements at the Collapse Prevention (CP) level decreased by up to 23% in the irregular structure with retrofitting compared to its non-retrofitted counterpart. Additionally, interstory drift ratios were more uniform post-retrofit, with Drift Concentration Factor (DCF) values approaching 1.0 across all performance levels, reflecting reduced variability in seismic response. The global ductility of the retrofitted buildings improved, with displacement ductility ratios increasing by up to 29%. These results underscore the effectiveness of RWs in enhancing global ductility, mitigating soft story failures, and providing a more predictable deformation pattern during seismic events. The study thus provides valuable insights into the robustness and cost-effectiveness of using rocking walls for retrofitting irregular RC buildings.

• Computers and Concrete
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• v.18 no.5
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• pp.951-968
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• 2016

In this study, pullout capacities of post-installed deformed bars anchored in low strength concrete using different bonding materials are investigated experimentally. The experimental study was conducted under outdoor and indoor conditions; on the beams of an actual reinforced concrete building and on concrete bases constructed at Istanbul Technical University (ITU). Ready-mixed cement based anchorage mortar with modified polymers (M1), ordinary cement with modified polymer admixture (M2), and epoxy based anchorage mortar with two components (E) were used as bonding material. Furthermore, test results are compared with the predictions of current analytical models. Findings of the study showed that properly designed cement based mortars can be efficiently used for anchoring deformed bars in low quality concrete. It is important to note that the cost of cement based mortar is much lower with respect to conventional epoxy based anchorage materials.