• Structural Engineering and Mechanics
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• v.81 no.3
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• pp.349-365
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• 2022

Steel fibre-reinforced concrete (SFRC) is an emerging class of composite for construction. However, a reliable method to assess the flexural behaviour of SFRC structural member is in lack. An analytical technique is proposed for determining the moment-curvature response of concrete beams reinforced with steel fibres and longitudinal bars (R/SFRC members). The behaviour of the tensile zone of such members is highly complex due to the interaction between the residual (tension softening) stresses of SFRC and the tension stiffening stresses. The current study suggests a transparent and mechanically sound method to combine these two stress concepts. Tension stiffening is modelled by the reinforcement-related approach assuming that the corresponding stresses act in the area of tensile reinforcement. The effect is quantified based on the analogy between the R/SFRC member and the equivalent RC member having identical geometry and materials except fibres. It is assumed that the resultant tension stiffening force for the R/SFRC member can be calculated as for the equivalent RC member providing that the reinforcement strain in the cracked section of these members is the same. The resultant tension stiffening force can be defined from the moment-curvature relation of the equivalent RC member using an inverse technique. The residual stress is calculated using an existing model that eliminates the need for dedicated mechanical testing. The proposed analytical technique was validated against test data of R/SFRC beams and slabs.

• Computers and Concrete
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• v.4 no.5
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• pp.403-424
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• 2007

The investigation of corrosion effects on the tensile behavior of reinforced concrete (RC) members is very important in region prone to high corrosion conditions. In this article, an experimental study concerning corrosion effects on tensile behavior of RC members is presented. For this purpose, a comprehensive experimental program including 58 cylindrical reinforced concrete specimens under various levels of corrosion is conducted. Some of the specimens (44) are located in large tub containing water and salt (5% salt solution); an electrical supplier has been utilized for the accelerated corrosion program. Afterwards, the tensile behavior of the specimens was studied by means of the direct tension tests. For each specimen, the tension stiffening curve is plotted, and their behavior at various load levels is investigated. Average crack spacing, loss of cross-section area due to corrosion, the concrete contribution to the tensile response for different strain levels, and maximum bond stress developed at each corrosion level are studied, and their appropriate relationships are proposed. The main parameters considered in this investigation are: degree of corrosion ($C_w$), reinforcement diameter (d), reinforcement ratio (${\rho}$), clear concrete cover (c), ratio of clear concrete cover to rebar diameter (c/d), and ratio of rebar diameter to reinforcement percentage ($d/{\rho}$).

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.198-201
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• 2006

In order to evaluate the seismic performance of reinforced concrete bridge piers, an inelastic time-dependent element is proposed. The proposed element enables increased characteristics due to structural intervention (i.e., repair and retrofitting) to be accurately reflected to the degraded strength and stiffness of the members. Comparative studies are conducted for reinforced concrete bridge columns being repaired and retrofitted and show good correlation between analytical prediction and experimental results. In addition, a nonlinear time-history analysis of a reinforced concrete bridge under multiple earthquakes confirms the applicability and effectiveness of the present development.

• Composites Research
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• v.23 no.4
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• pp.44-51
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• 2010

Recently, to solve the problems associated with the neutralization and corrosion of reinforced concrete compression members, the structural configurations such as CFFT (Concrete Filled GFRP Tube) and RCFFT (Reinforced Concrete Filled GFRR Tube) have been developed and applied to main members of civil engineering structure. These members can increase structural performance in terms of structural stability, ductility as well as chemical resistance compared with conventional concrete structural members. Many researches in numerous institutions to predict the load carrying capacity of the concrete compression member strengthened with FRP materials have been conducted and they have been suggested an equation for the prediction of the load carrying capacity of the members. Through the review of the research results, it was found that their results are similar each other. Moreover, it was also found that the results are not directly applicable to our specimens since the results are largely depended upon the member configurations. Also, since the accurate design criteria for the RC members strengthened with FRP such as RCFFT have not been established properly, relevant theoretical and experimental investigations must be conducted for the application to the practical structures. In this study, structural behavior of RCFFT was evaluated through compressive and quasi-static flexural tests in order to formulate design criteria for the structural design. In addition, the RCFFT members were also investigated to examine their confinement effect and the equations capable of estimating the compressive ultimate strength and flexural stiffness of the RCFFT members were proposed.

• Magazine of the Korea Concrete Institute
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• v.15 no.2
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• pp.68-75
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• 2003

• Magazine of the Korea Concrete Institute
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• v.26 no.6
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• pp.43-46
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• 2014

• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.553-560
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• 2001

The ductility capacity should be estimated for inelastic analysis and design of reinforced concrete flexural members. Therefore, to estimate the ductility capacity, the model of moment-curvature relationship of reinforced concrete flexural member is assumed in this study. The curvature, rotation, and displacement(deflection) of reinforced concrete cantilever beams are analyzed and tested. The analytical results are compared with the test results. According to the analytical and test results, the assumed model of moment-curvature relationship in this study is adequate in flexural analysis of reinforced concrete members because the analytical results are well agreed with the test results, and it is resonable to express the ductility capacity in the rotation or displacement ductility, Because the curvature ductility is the limited index in a certain section. It is investigated that the ductility capacity is proportional to lateral reinforcement and compression reinforcement and inversely proportional to tension reinforcement.

• Steel and Composite Structures
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• v.18 no.5
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• pp.1129-1144
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• 2015

Based on the experiment, this paper focuses on studying flexural behavior of splicing concrete-filled glass fiber reinforced polymer (GFRP) tubular composite members connected with steel bars. The test results indicated the confinement effects of GFRP tubes on the concrete core in compression zone began to produce, when the load reached about $50%P_u$ ($P_u$-ultimate load), but the confinement effects in tensile zone was unobvious. In addition, the failure modes of composite members were influenced by the steel ratio of the joint. For splicing unreinforced composite members, the steel ratio more than 1.96% could satisfy the splicing requirements and the steel ratio 2.94% was ideal comparatively. For splicing reinforced specimen, the bearing capacity of specimen with 3.92% steel ratio was higher 21.4% than specimen with 2.94% steel ratio and the latter was higher 21.2% than the contrast non-splicing specimen, which indicated that the steel ratio more than 2.94% could satisfy the splicing requirements and both splicing ways used in the experiment were feasible. So, the optimal steel ratio 2.94% was suggested economically. The experimental results also indicated that the carrying capacity and ductility of splicing concrete-filled GFRP tubular composite members could be improved by setting internal longitudinal rebars.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.53-58
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• 2003

Carbon fiber sheet has been used to rehabilitate many types of reinforced concrete members with its superior characteristics such as their lightweight, high strength, corrosion resistance, and easy execution. But the failure behavior of reinforced concrete members show a high variation by the bond characteristics between carbon fiber sheet and concrete surface. In this study, a bond stress-slip model, which accounts for changes in bonding behavior between concrete and carbon fiber sheet with some link elements, is proposed. The link elements are used to represent the concrete-carbon fiber sheet interface. To investigate the efficiency of this method, the analytical solutions for the behavior of reinforced concrete beam strengthened with carbon fiber sheet are compared with experimental ones. Results from the proposed model comparatively well agree with the experimental results.

• KCI Concrete Journal
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• v.14 no.3
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• pp.111-120
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• 2002

This study proposes a joint model consisting of different types of members as a new structural system, and then investigates the resulting structural behavior. The joint model consists of a concrete-filled steel tube column (CFT) together with a steel reinforced concrete at the end plus reinforced concrete beam at the center. For comparison, two other joint models were designed, that are, a CPT with a reinforced concrete beam, and a CFT with a steel reinforced concrete at the end plus steel concrete beam at the center, then their joint capacity and rigidity, energy absorption capacity, etc., were all investigated. From the results, the CFT column with a steel reinforced concrete at the end plus steel concrete beam at the center was outstanding in terms of its capacity and rigidity. The results of this analysis demonstrate that an adequate connection type and reinforcement method with different materials of increasing the rigidity, thereby producing a capacity improvement along with protection from pre-fractures.