• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.179-183
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• 1993

Loads acting on concrete structures are completely random in nature with respect to frequency, magnitude and order of loading, and are essentially distinct from the loads in two-stage and variable load fatigue test. Thus, this study proposes the fatigue test method generating random loads based on the analyzed result.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.343-351
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• 2005

This study developed a shear strength prediction model of FRP strengthened reinforced concrete beams in shear. The primary design parameters were shear crack angle and shear span to depth ratio of FRP reinforcement. Of primary concern In the suggested model was the FRP debonding failure, which Is a typical fracture mode of RC beams strengthened with FRP, The proposed model used a crack sliding model based on modified plasticity theory. To address the effect of the shear span to depth ratio, the arch action was considered in the proposed model. The proposed model was applied to RC beams strengthened with FRP. The results showed that the proposed model agree with test results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.1 s.71
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• pp.1-13
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• 2006

An analytical procedure to analyze reinforced concrete(RC) beams and columns subject to monotonic and cyclic loadings is proposed on the basis of the layered section method. In contrast to the classical nonlinear approaches adopting the perfect bond assumption, the bond slip effect along the reinforcing bar is quantified with the force equilibrium and compatibility condition at the post cracking stage and its contribution is implemented into the reinforcing. The advantage of the proposed analytical procedure, therefore, will be on the consideration of the bond slip effect while using the classical layered section method without additional consideration such as taking the double nodes. Through correlation studies between experimental data and analytical results, it Is verified that the proposed analytical procedure can effectively simulate the cracking behavior of RC beams and columns accompanying the stiffness degradation caused by the bond slip.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.473-480
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• 2012

In order to develop an effecive seismic strengthening metghod for existing concrete structure, structural tests of aramid FRP reinforced RC columns are performed. The test variables were strengthening methods of aramid sheet and strip. The test results were evaluated by comparing strength and energy dissipation capacities of non-reinforced and reinforced specimens. The test result comparison showed that aramid sheet reinforcement on RC column was evaluated as the most efficient way to increase strength and energy dissipation capacity.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.456-463
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• 2005

An analytical procedure to analyze reinforced concrete (RC) beams subject to monotonic loadings is proposed on the basis of the moment-curvature relations of RC sections. Unlike previous analytical models which result the overestimation of stiffnesses and underestimation of structural deformations induced from ignoring the shear deformation and assuming perfect-bond condition between steel and concrete, the proposed relation considers the rigid-body-motion due to anchorage slip at the fixed end. The advantages of the proposed relation, compared with the previous numerical models, are on the promotion in effectiveness of analysis and reflection of influencing factors which must be considered in nonlinear analysis of RC beam by taking into account the nonlinear effects into the simplifying moment-curvature relation. Finally, correlation studies between analytical and experimental results are conducted to establish the applicability of the proposed model to the nonlinear analysis of RC structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.548-551
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• 2004

The main purpose of this study is to estimate the internal temperature of RC beam under fire. For this purpose, the finite difference method was used. In the previous studies, the structural behavior of fire damaged RC beams was investigated through experiments. The result was concluded that The high temperature affects the properties of concrete such as the elastic modulus, the compressive strength. The internal temperature Estimation of the concrete is helpful for understanding the structural behavior of fire damaged RC beams. Especially, high strength concrete has more spalling than normal strength one. So, this study is performed analysis of internal temperature of RC beam considering spalling.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.177-180
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• 2005

The specified tensile strength provided by the manufacturer is determined on the basis of the reliable lower limit ($X-3{\sigma}$ : X=average tensile strength, $\sigma$=standard deviation) obtained from the material test results. Most of these data, however, are based on the test results of 1 layer of FRP sheet. Also, the partial strength reduction factor for strengthening RC members with FRP is based on the small-scale model tests. But, the failure mechanisms of small-scale model tests are reported to be different from those of the full-scale tests. This paper present the test results of full-scale RC beams strengthened with multi-layer GFRP sheets up to 3 layer as well as the material tests. From the material tests, it was observed that the average tensile strengths of GFRP sheets are decreased as the number of layer are increased. Also the premature debonding failure of RC beams strengthened with multi-layer GFRP sheets are observed in inverse proportion to the number of GFRP sheets

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.255-258
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• 2005

The current ACI design code does not take into account the contribution of concrete for the torsional moment of reinforced concrete(RC) beams subjected to pure torsion. This code is not capable of evaluating the inter-effects between concrete and torsional reinforcement on the torsional resistance of the RC beams. In this study, 9 RC beams subjected to pure torsion were tested. The main parameter of the beams was the amount of torsional reinforcement and the angle of twist. Test results indicated that the current ACI code over-estimated the torsional strength of RC beams that had larger amount of torsional reinforcement.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.283-286
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• 2005

The effectiveness of shear strengthening with glass fiber sheets on normal or low strength RC beams have been investigated experimentally. A design compressive strength of concrete of 13.5MPa has been planned considering the degradation state of the existing structure to be strengthened in this study. Also, concrete surface reinforcing agent was applied to increase bond capacity between concrete and GFRP sheets in case of low strength RC beams. Comparing the test results of low and normal strength beams strengthened with GFRP sheets indicated that total shear capacity of beams was decreased with concrete strength decreased, but the shear strengthening capacity of GFRP sheets are hardly affected by concrete strength. In addition, shear strengthening effects of RC beams strengthened with GFRP sheets can be estimated by $\rho_w{\cdot}f_w$ based on the maximum effective strain of FRP sheet proposed by ACI 440.2R recommendation.

• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.69-80
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• 1999

The strengthening of reinforced concrete structures by externally bonded GFRP has become increasingly common in resent years. However the analysis and design method for GFRP plate strengthening of RC beams is not well established yet. The purpose of present paper is, therefore, to define the failure mechanism and failure behavior of strengthened RC beam using GFRP and then to propose a resonable method for the calculation of interface debonding load for those beams. From the experimental results of beams strengthened by GFRP, the influence of length and thickness, width of plate on the interfacial debonding failure behavior of beam is studied and, on the basis of test results, the semi-empirical equation to predict debonding load is developed. The proposed theory based on nonlinear analysis and critical flexural crack width, predicts relatively well the debonding failure load of test beams and may be efficiently used in the analysis and design of strengthened RC beams using GFRP.