• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2797-2803
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• 2012

This paper presents the pull-out behaviors of headed glass fiber reinforced polymer (GFRP) rebar embedded in mortar under tension loading. Five specimens with headed GFRP rebars that were anchored in the center of mortar bases were constructed and the pull-out test was conducted. To verify the test results, the finite element analysis was conducted and the results were compared with the FE analysis using ANSYS software package. Based on the test results it was indicated that the CCD(concrete capacity design) failure theory should be adopted and not to use the 45o cone failure theory as the breakout capacity in the headed GFRP rebar embedded in mortar.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.501-502
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• 2009

This paper presents a strengthening technique of weakened telegraph pole using an inflating agent to adjust chemical pre-stressing. The strengthening technique increases only resisting capacity and ductility of telegraph but also limited quantity and application ability of FRP. The chemical pre-stressing and the resisting capacity are investigated experimentally. From the results, it is confirmed that it is possible to control the degree of applied pre-stressing by controlling the amount of inflating agent. In addition, the pre-stressing can increase resisting capacity up to three times compared with no pre-stressing.

• Steel and Composite Structures
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• v.17 no.3
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• pp.271-285
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• 2014

This paper aims to examine the behavior of slender reinforced concrete columns confined with external glass fiber reinforced polymers (GFRP) sheets under eccentric loads. The experimental work conducted in this paper is an extension to previous work by the author concerning the behavior of eccentrically loaded short columns strengthened with GFRP wrapping. In this study, nine reinforced concrete columns divided into three groups were casted and tested. Three eccentricity ratios corresponding to e/t = 0, 0.10, and 0.50 in one direction of the column were tested in each group. The first group was the control one without confinement with slenderness ratio equal 20. The second group was the same as the first group but fully wrapped with one layer of GFRP laminates. The third group was also fully wrapped with one layer of GFRP laminates but having slenderness ratio equal 15. The experimental results of another two groups from the previous work were used in this study to investigate the difference between short and slender columns. The first was control one with slenderness ratio equal 10 and the second was fully wrapped and having the same slenderness ratio. All specimens were loaded until failure. The ultimate load, axial deformation, strain in steel bars, and failure mechanisms of each specimen were generated and analyzed. The results show that GFRP laminates confining system is less effective with slender columns compared with short one, but this solution is still applied and it can be efficiently utilized especially for slender columns with low eccentric ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.339-342
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• 2000

Recently, the importance of the conutermeasures for waste materials has pointed out. Waste glass is also one to waste materials used for the recycling in construction sites. The crushed waste glass has been used to make a glass polymer composite that can be applied for sewer, storm drain pipe and interlocking block, etc. In this study, the crushed waste glass is explored with the possibility of recycling it, as a substitute for fine aggregates. The prepose of this investigation is to improve the strengths and acid resistance of the UP mortars using crushed waste glass. The UP mortars are prepare with blast furnace slag fly ash filler. the UP-fine aggregate ratios the crushed waste glass replacements for fine aggregate are tested strengths before and after immersion(H (아래첨자2)SO(아래첨자4) 10%), weight change and acid resistance are also tested. From the test results, the relative strength or UP mortars using fly ash as filler are found to be somewhat superior to that of the UP mortars using blast furnace as filler, And a UP mortar with fly ash as a filler, a UP-fine aggregate ratio of 15% and a waste glass replacement if 50% for fine aggregate is recommended as optimal mix proportion of UP mortar using crushed waste glass. Accordingly, it is enough to assure the use of the crushed waare glass as an aggregate for the production of UP mortar.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.261-266
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• 2003

This study is to investigate the heating value and noxious gases generation such as CO, NO and $SO_2$ known as dangerous gas for human from specimen made of cement and lightweight aggregate. The most quanity of CO gas is generated in EPS(Expanded Poly Styrene), core of commercial sandwich panel. Although specimens mainly composed of cement discharged the relatively less CO gas than organic core such as EPS, specimens which SBR was added discharged the very much amount of CO gas similar to EPS and especially, specimens including foaming agent, gas foaming agent or redipersible powder of VA/VeoVa showed the good properties in the generation of CO gas. From the standpoint of the generation of NO and $SO_2$ gas, both the core of commercial sandwich panel such as EPS, Glass wool and specimens made with polymer dispersion such as St/BA and SBR discharge the very much amount of NO and $SO_2$ gas in comparison of the other specimens. From this study, it was confirmed that organic materials such as core of commercial sandwich panel dischared much more noxious gas than specimens composed of cement and inorganic lightweight aggregate.

• Structural Engineering and Mechanics
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• v.30 no.2
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• pp.247-261
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• 2008

Performance of shear-deficient reinforced concrete (RC) beams strengthened with carbon fiber-reinforced polymer (CFRP) strips/sheets is analyzed through numerical simulations on four-point bending tests. The numerical simulations are carried out using the finite element (FE) program ABAQUS. A micromechanics-based constitutive model (Liang et al. 2006) is implemented into the FE program ABAQUS to model CFRP strips/sheets. The predicted results are compared with experiment data (Khalifa and Nanni 2002) to assess the accuracy of the proposed FE analysis approach. A series of numerical tests are conducted to investigate the influence of stirrup lay-ups on the shear strengthening performance of the CFRP strips/sheets, to illustrate the influence of the damage parameters on the microcrack density evolution in concrete, and to investigate the shear and flexural strengthening performance of CFRP strips/ sheets. It has been shown that the proposed FE analysis approach is suitable for the performance prediction of RC beams strengthened with CFRP strips/sheets.

• Structural Engineering and Mechanics
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• v.67 no.1
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• pp.45-52
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• 2018

Several techniques have been developed for shear strengthening of reinforced concrete (RC) members by using fiber reinforced polymer (FRP) composites. However, debonding of FRP retrofits from concrete substrate still deemed as a challenging concern in their application which needs to be scrutinized in details. As a result, this paper reports on the results of an experimental investigation on shear strengthening of RC beams using near surface mounted (NSM) FRP reinforcing bars. The main objective of the experimentation was increasing the efficiency of shear retrofits by precluding/postponing the premature debonding failure. The experimental program was comprised of six shear deficient RC beams. The test parameters include the FRP rebar spacing, inclination angle, and groove shape. Also, an innovative modification was introduced to the conventional NSM technique and its efficiency was evaluated by experimental observation and measurement. The results testified the efficiency of glass FRP (GFRP) rebars in increasing the shear strength of the test specimens retrofitted using conventional NSM technique. However, debonding of FRP bars impeded exploiting all retrofitting advantages and induced a premature shear failure. On the contrary, application of the proposed modified NSM (MNSM) technique was not only capable of preventing the premature debonding of FRP bars, but also could replace the failure mode of specimen from the brittle shear to a ductile flexural failure which is more desirable.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.191-195
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• 2009

After developing the pre-crack to simulate a damaged reinforced concrete beam, fatigue test was conducted on the beam repaired by GFRP Bar and GSP embedded method. In the result of fatigue test, most residual displacement and crack of the experimental beams occurs in the early loading cycle and an increasing rate of these due to number of cycles were insignificant. Comparing with a non-repaired beam, a static strength of the repaired beam greatly increased, but fatigue strength decreased. In S-N curves, fatigue strength of the beam repaired by GFRP Bar and GSP was 58%, 52% of the static strength respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2396-2402
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• 2012

In recent years, the use of hybrid fiber reinforced polymer(FRP)-concrete members with a dual purpose of both formwork and reinforcement, has been considered in some structures and has been applied in a small number of bridge decks. Numerical simulations of the beam failure tests were performed using nonlinear finite element program and a parametric study was performed with variables of perfobond shape. The ultimate strength was increased with perfobond shape because of dowel action. It was showed a good performance in case of approximately perforate diameter 25~35mm in this case.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.229-235
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• 2018

This study investigated the behaviour of the simply supported hollow steel tube (HST) beams, either concrete filled or unfilled when strengthened with carbon fibre reinforced polymer (CFRP) sheets. Eight specimens with varied tubes thickness (sections classification 1 and 3) were all tested experimentally under static flexural loading, four out of eight were filled with normal concrete (CFST beams). Particularly, the partial CFRP strengthening scheme was used, which wrapped the bottom-half of the beams cross-section (U-shaped wrapping), in order to use the efficiency of high tensile strength of CFRP sheets at the tension stress only of simply supported beams. In general, the results showed that the CFRP sheets significantly improved the ultimate strength and energy absorption capacities of the CFST beams with very limited improvement on the related HST beams. For example, the load and energy absorption capacities for the CFST beams (tube section class 1) were increased about 20% and 32.6%, respectively, when partially strengthened with two CFRP layers, and these improvements had increased more (62% and 38%) for the same CFST beams using tube class 3. However, these capacities recorded no much improvement on the related unfilled HST beams when the same CFRP strengthening scheme was adopted.