• Steel and Composite Structures
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• v.27 no.5
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• pp.633-646
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• 2018

This study investigated the seismic performance of a hybrid damper composed of a steel slit plate and friction pads, and an optimum retrofit scheme was developed based on life cycle cost. A sample hybrid damper was tested under cyclic loading to confirm its validity as a damping device and to construct its nonlinear analysis model. The effectiveness of the optimum damper distribution schemes was investigated by comparing the seismic fragility and the life cycle costs of the model structure before and after the retrofit. The test results showed that the damper behaved stably throughout the loading history. Numerical analysis results showed that the slit-friction hybrid dampers optimally distributed based on life cycle cost proved to be effective in minimizing the failure probability and the repair cost after earthquakes.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.659-664
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• 1997

RC structures can deteriorate for many defective factors. In the repair and retrofit works of concrete, epoxy resins are widely used as repair materials. The object of this study is to investigate the material properties and durabilities of epoxy resins which are commonly used in repairing concrete. The material properties such as line-expansion modulus, viscosity, microstructure and physical parameter as well as the durabilities such as gravity change, tensile strength, elongation change were carried out.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.71-80
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• 2007

Because of the characteristics relating to high tensile ductility, High Performance Fiber Reinforced Cementitious Composites (HPFRCC) are studied to be adopted in repair and retrofit of buildings. A series of three shear wall specimens was tested under constant axial stress and reversed cyclic lateral loading in order to evaluate the seismic retrofit that had been proposed for the shear wall with the opening. The retrofit involved the use of newly developed ECC and MDF(Macro Defect Free), both of which are sprayed through the high pressure pump, over the entire face of the wall. The results indicate that two difference types of retrofitting strategy make the different effects of a rise in the strength and ductility of each specimen.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.50-55
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• 2008

In order to investigate and estimate the cause of fatigue crack occurred to curved girder bridge that is used during 20 years, in this study, filed tests to obtain the characteristic of stress hysteresis were performed under the real traffic flows. From these test results, we analyzed the cause of fatigue crack for various fatigue crack patterns. Also, the characteristic of structural behavior for the curved girder bridge were examined from the FE analysis. In addition, to retrofit various fatigue cracks occurred in the bridge, FE analyses considering the characteristics of crack patterns were performed and retrofitting methods were suggested.

• Journal of Korean Association for Spatial Structures
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• v.20 no.4
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• pp.177-184
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• 2020

This study evaluates safety assessment before and after repair of Seonamsa temple seungseon bridge, which refer to the representative Hongye bridge in Korea. In this approach natural frequency of the structure were considered in the modeling procedure. Trial & error method is applied to obtain the approximate natural frequency before and after retrofit construction. Stiffness of the actual structure was examined to account for the dynamic characteristics of Hongye bridge measured in the field and adjusting parameters in computer modeling. The safety and usability of the stone structure in terms of load bearing capacity and displacement were examined.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.397-400
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• 2006

Most of the civil structures in Korea and abroad have many kinds of damages when they are facing over-loaded traffics, long-term serviceability, and severe environmental conditions. Repair, rehabilitation, and retrofit are important for maintaining the serviceability of structures. In recent year, VES-LMC has been widely used as repair material for bridge deck repair and rehabilitation, because the VES-LMC has a various benefits such as traffic opening after 3 hours of curing, higher durability and bond strength. In case of any structure repaired or rehabilitated with VES-LMC, those were influenced capacity of bond between the base layer of slab and VES-LMC as well as physical properties of each other materials. The capacity of bond depended on purity of interface, micro cracks, curing of VES-LMC and so like. A kind of popular concrete repair technique, High pressure water jetting equipment is extremely efficient at removing damaged concrete. Removing damaged or poor quality concrete from sensitive structures such as bridge, tunnels, multi-story car parking decks and runways, using the high pressure water jetting could remove damaged or poor quality concrete remaining healthy and sound concrete. Accordingly, the purpose of this study is that it was to evaluate effect of hydrodemolition on the bond strength of VES-LMC overlay compared with effects of other method such as breaker, untreated. Also, it was evaluated the effect of surface moisture.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.05a
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• pp.227-232
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• 1998

강상형교(Steel Box Girder Bridge)는 휨강성 및 비틀림강성이 I형이나 II형 단면에 비해서 현저하게 크고 가설시의 안전성도 우수하며, 완성후의 내하력도 크다는 장점을 갖고 있어 지간이 40-80m인 교량에 적용되는 대표적인 교량형식이며, 또한 경제적, 구조적인 특성을 고려하여 대분분이 연속교 형식으로 건설되고 있다. (중략)

• Earthquakes and Structures
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• v.10 no.3
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• pp.613-628
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• 2016

The effectiveness of the use of modern repair schemes for the seismic retrofit of existing RC structures were assessed on a comparative experimental study of carbon fiber-reinforced polymer (CFRP) strips and sheets for the repair of reinforced concrete members of RC frames, damaged because of cyclic loading. Two virgin, single - story, one - bay, 1/3 - scale frame specimens were tested under cyclic horizontal loading, up to a drift level of 4%. Then, virgin specimens, B and F, respectively, were repaired and retested in the same way. One, specimen RB, was repaired with epoxy injections and CFRP strips and one, specimen RF, was repaired with epoxy injections and CFRP sheets. The two specimens are used to examine the differences between the structural behavior of frames repaired using CFRP strips and frames repaired using CFRP sheets. Both qualitative and quantitative conclusions, based on the observed maximum loads, loading and reloading stiffness, hysteretic energy absorption and failure mechanisms are presented and compared. The repaired frames recovered their strength, stiffness and energy dissipated reasonably. The use of CFRP sheets was found more effective than CFRP strips, due to the proper anchorage.

• Structural Engineering and Mechanics
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• v.70 no.2
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• pp.133-141
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• 2019

The aim of the present paper is to present the cyclic behavior of strengthened reinforced concrete shear wall test specimen, which was reinforced with cold drawn welded wire mesh fabric. Two reinforced concrete shear wall specimens have been tested in the present study. The walls were tested under reversed cyclic loading with loading applied near the tip of the walls. The control wall is tested in its original state to serve as a baseline for the evaluation of the repair and strengthening techniques. The two test specimens include a control wall and a repaired wall. The control wall test specimen was designed and detailed to simulate non-ductile reinforced concrete shear walls that do not meet the modern seismic provisions. The response of the original wall was associated with the brittle failure. The control shear wall was repaired by addition of the reinforcements and the concrete and then it was reloaded. The effectiveness of the repair technique was investigated. Test results indicate that there can be a near full restoration of the walls' strength. The data from this test, augmenting other data available in the literature, will be useful in calibrating improved analytical methods as they are developed.

• Earthquakes and Structures
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• v.15 no.6
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• pp.617-627
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• 2018

After earthquakes FRP sheets are often used for the rehabilitation of damaged Reinforced Concrete (RC) beamcolumn connections. Connections with minor to moderate damage are often dealt with by applying FRP sheets after a superficial repair of the cracks using resin paste or high strength mortar but without infusion of thin resin solution under pressure into the cracking system. This technique is usually adopted in these cases due to the fast and easy-to-apply procedure. The experimental investigation reported herein aims at evaluating the effectiveness of repairing the damaged beam-column connections using FRP sheets after a meticulous but superficial repair of their cracking system using resin paste. The investigation comprises experimental results of 10 full scale beam-column joint specimens; five original joints and the corresponding retrofitted ones. The repair technique has been applied to RC joints with different joint reinforcement arrangements with minor to severe damage brought about by cyclic loading for the purposes of this work. Aiming at quantitative concluding remarks about the effectiveness of the repair technique, data concerning response loads, loading stiffness and energy absorption values have been acquired and commented upon. Furthermore, comparisons of damage index values and values of equivalent viscous damping, as obtained during the test of the original specimens, with the corresponding ones observed in the loading of the repaired ones have also been evaluated and commented. Based on these comparisons, it is deduced that the technique under investigation can be considered to be a rather satisfactory repair technique for joints with minor to moderate damage taking into account the rapid, convenient and easy-to-apply character of its application.