• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.328-333
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• 1996

Concrete can be defective for several reasons, including an inadequate design, material selection of workmanship, failure to appreciate the hazards associated with prevailing enviromental conditions. Concrete can also deteriorate or be damaged in use. Thus, it is necessary to evaluate the safety of existing concrete strucutres. On the basis of these reasons, they must be performed for repair or rehabilitation. Presently, strengthening methods of R/C structure used in Korea, are an enlargement of concrete member, strengthening with steel plate or CFRP on the R/C structure. It has been widely estabilished that strengthening effect of CFRP is superior to steel plate in terms of it's lighter unit weight and higher tensile strength. But there are no construction results of CFRP on the civil R/C structure in Korea. The strengthening design technique with CFRP, it's const겨ction, and it's strengthening effect for deteriorated R/C rahmen bridge is introduced in this paper.

• International Journal of Concrete Structures and Materials
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• v.6 no.3
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• pp.199-207
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• 2012

Concrete is an economical construction material and for that reason it is widely used in buildings and infrastructures. The use of deicing salts, expansion joint failure, and freeze-thaw cycles have led to concrete bridge girders experiencing corrosion of steel reinforcement and becoming unsafe for driving. The goal of this research is to assess the effectiveness of current and possible repair techniques for the end region of damaged prestressed concrete girders. To do this, three American Association of State Highway and Transportation prestressed concrete girders were tested to failure, repaired, and retested. Three different repair materials were tested including carbon fiber, glass fiber, and surface mounted rods. Each different repair material was also tested with and without injected epoxy. Comparisons were then made to determine if injecting epoxy had a positive effect on stiffness and strength recovery as well as which repair type regained the largest percentage of original strength.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.361-368
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• 2012

Required performance for repair materials are strength, ductility, durability and bonding with the substrate concrete. Various kinds of fiber-reinforced cement composites (FRCCs) have been developed and used as repair materials. Strain-hardening cement based composites (SHCC) is one of the effective repair materials that can be used to improve crack-damage tolerance of reinforced concrete (RC) structures. SHCC is a superior FRCC that has multiple cracking characteristic and pseudo strain-hardening behavior. The expansive admixture, which can be used to reduce shrinkage in SHCC materials with less workability by controlling interfacial bonding performance between SHCC and substrate concrete. For the application of SHCC as a repair material to RC structures, this study investigates the flexural performance of expansive SHCC-layered concrete beam. Test variables include the replacement levels of expansive admixture (0 and 10%), repair thickness (30 and 40 mm), and compressive strength of SHCC (30, 70 and 100 MPa). Four point bending tests on concrete beams strengthened with SHCCs were carried out to evaluate the contribution of SHCC on the flexural capacity. The result suggested that expansive SHCC materials can be used for repairing and strengthening of concrete infrastructures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.183-189
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• 2006

When RC structures are repaired or strengthened using FRP, it is required to cure for some Period under certain air temperature and then it is hopeful to avoid detrimental action caused by external vibration sources during that period. Therefore, an effect of repeated loading during Carbon Fiber Sheet(CFS) strengthening Process on the strengthening efficiency is studied through an experiment for a number of RC beams. Experimental results showed that the curing time of 24 hours without any repeated loading after CFS attachment were recommended for 1 ply strengthening, and 12 hours for 2 plies strengthening.

• Advances in concrete construction
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• v.9 no.1
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• pp.1-7
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• 2020

Retrofitting is an alteration of existing member or component of the structure. In civil engineering point of view, it is called strengthening of the old structure. Deterioration of structures may be due to aging, corrosion, failure of joints, earthquake forces, increase in service loads, etc. Such structures need urgent repair, retrofitting and strengthening to avoid collapse, cracking and loss in strength or deflection. Advanced techniques are required to be developed for the repair of structural components to replace conventional techniques. This paper focuses exclusively on torsional behaviour of Reinforced Concrete (RC) beams and retrofitted RC beams wrapped with aramid fiber. Beams were retrofitted with aramid fiber by full wrapping and in the form of 150 mm wide strips at a spacing of 100 mm, 150 mm, 200 mm respectively using epoxy resin and hardener. A total 15 numbers of RC beams of 150 mm×300 mm×1300 mm in size were cast, 3 beams are tested as control specimens, and 12 beams are tested for torsion up to the failure and then retrofitted with aramid fiber. Experimental results are validated with the help of data obtained by finite element analysis using ANSYS. The full wrapping configuration of aramid fiber regains 105% strength after retrofitting. With the increase in spacing of fabric material, torsional strength reduces to 82% with about 45% saving in material.

• Structural Engineering and Mechanics
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• v.13 no.1
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• pp.17-34
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• 2002

The use of local two-sided and three-sided jacketing for the repair and strengthening of reinforced concrete beam-column joints damaged by severe earthquakes is investigated experimentally and analytically. Two exterior beam-column joint specimens ($O_1$ and $O_2$) were submitted to a series of cyclic lateral loads to simulate severe earthquake damage. The specimens were typical of existing older structures built in the 1960s and 1970s. The specimens were then repaired and strengthened by local two-sided or three-sided jacketing according to UNIDO Manual guidelines. The strengthened specimens ($RO_1$ and $RO_2$) were then subjected to the same displacement history as that imposed on the original specimens. The repaired and strengthened specimens exhibited significantly higher strength, stiffness and better energy dissipation capacity than the original specimens.

• Journal of the Korean Professional Engineers Association
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• v.45 no.4
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• pp.62-66
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• 2012

An effective management of reservoir, an agricultural infrastructure, requires an establishment of a good management system by means of unification of managing entity; training of manpower and their deployment for scientific management by expert group; carrying out repair / strengthening works based on periodic in-depth inspection results. In particular, continuous budget allocation as well as cultivating good management mind of managing entity are essential for undertaking periodic precise and / or in-depth inspections for assessing the functionality / safety of facilities and proper repair / strengthening works for satisfying the up-to-date facilty standarda and changing environmental conditions.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.103-114
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• 2000

Recently, the need for strengthening reinforced concrete and prestressed concrete structure is increasing, particularly when there is an increase in load requirements, a change in use, a degradation problem, or some design/construction defects. Therefore, use of composite materials for structural repair presents several advantages and has been investigated all over the world. In this paper, the reinforced concrete slabs with epoxy - bonded AFRP sheed were experimentally investigated. Experimental data on strength. stiffness, material strain, deflection and mode of failure of strengthened slabs were obtained, and comparisons between the different flexural reinforcing schemes and reinforced concrete slabs without AFRP sheets were made It can be concluded that flexural strength of RC slabs strengthened with AFRP has increased, and that ductility of strengthened slabs has decreased.

• Journal of the Korea institute for structural maintenance and inspection
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• v.1 no.1
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• pp.125-132
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• 1997

This study was intended to investigate the effects of epoxy grout on compressive strength for damaged concrete structures. For this purpose, concrete molds were manufactured and tested for compressive strength at 28 days after water curing. Two kinds of Korea-made and one Japan-made epoxy grouts were injected into the broken concrete molds with the automatic low-pressure injecting method or the hand injecting method.

• 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.