• Steel and Composite Structures
• /
• v.44 no.6
• /
• pp.803-816
• /
• 2022

Composite materials are effective in forming externally bonded reinforcements which find applications related to existing structures repair, attributed to their high strength-to-weight ratio and ease of installation. Among various composites, fibre reinforced polymers (FRP) have somewhat been largely accepted as a commonly utilized composite for such purposes. It is only recently that steel fibres have been considered as additional members of the FRP fibre family, intuitively termed as steel reinforced polymer (SRP). Owing to its low cost and permissibility of fibre bending at sharp corners, SRP is rapidly becoming a viable contender to other FRP systems. This paper investigates the bond behaviour of SRP-concrete joints with different bonded lengths (50, 75, 100, 150 and 300 mm) and widths (15, 30, 40, 50, and 75 mm) using single-lap shear tests. The experimental specimens contain SRP strips with a fixed density of steel fibres (0.472 cords/mm) bonded to the face of concrete prisms. The load responses were obtained and compared in terms of corresponding load and slip boundaries of the constant region and the peak loads. The failure modes of SRP composites are discussed, and the range of effective bonded length is evaluated herein. In the end, a new analytical model was proposed to estimate the SRP-concrete bond strength using a genetic algorithm, which outperforms 22 existing FRP-concrete bond strength models.

• Journal of the Korea Concrete Institute
• /
• v.20 no.4
• /
• pp.459-467
• /
• 2008

This paper describes a proposal for average crack width and immediate deflection calculation in structural concrete members. The model is mathematically derived from actual bond stressslip relationships and tension stiffening effect between reinforcement and the surrounding concrete, and the actual strains of steel and concrete are integrated respectively along the embedded length between the adjacent cracks so as to obtain the difference in the axial elongation. With these, a model for average crack width and immediate deflection in reinforced concrete flexural members are proposed utilizing difference in the axial elongation and average steel strain and moment-curvature relationship with taking account of bond characteristics. The model is applied to the test specimens available in literatures, and the crack width and deflections predicted by the proposal equation in this study are closed to the experimentally measured data compared the current code provisions.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1991.10a
• /
• pp.17-22
• /
• 1991

An accurate and efficient analytical model describing the bond effect between reinforcing steel and concrete without taking the double nodes is presented. To increase the efficiency of the solution and reduce the number of degrees of freedom, the reinforcing bar elements are considered to be embedded in the connote elements. Relative douses of freedom accounting for the relative slip between reinforcing steel and concrete are condensed out during the stiffness formation phase. However, these degrees of freedom Can be taken into account explicitly by solving the constructed global equilibrium equation for each reinforcing steel. The usefulness of proposed model is established through the comparison with the experimental data subjected on push and push-pull loadings.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.902-907
• /
• 2003

Substantial experimental and theoretical work exists on the bond characteristics of FRP-concrete adhesive joints. Analytic solutions based on fracture mechanics are most commonly accepted for theoretical work on joint. The solutions may be derived for the simple form of the shear strees-slip curve. And it is difficult to determine the model parameters consisting the curve. In this study, the bilinear curve with softening branch is introduced. The model parameters are determined by the method described by the companion paper with comparison of test results. There are many uncertainties in the test results of CFRP sheet adhesive joints, so that test results used for the construction of the regression problem should be reasonably selected.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2002.10a
• /
• pp.475-482
• /
• 2002

A moment-curvature relationship to simulate the behavior of reinforced concrete (RC) columns under cyclic loading is introduced. Unlike previous moment4curvature models and the layered section approach, the proposed model takes into account the bond-slip effect by using a monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The pinching effect caused by axial force is considered with an assumption that the absorbing energy corresponding to any deformation level maintains constant regardless of the magnitude of applied axial lone. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. Finally, correlation studies between analytical result and experimental studies are conducted to establish the validity of the proposed model.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2000.10a
• /
• pp.190-197
• /
• 2000

A moment-curvature relationship to simulate the behavior of reinforced concrete beam under cyclic loading is introduced. Unlike previous moment-curvature models and the layered section approach, the proposed model takes into consideration the bond-slip effect by using monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. The modification of the moment-curvature relation to reflect the fixed-end rotation and pinching effect is also introduced. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed model.

• Journal of Ocean Engineering and Technology
• /
• v.14 no.2
• /
• pp.84-88
• /
• 2000

The main objectives of this study are to compare the obtained mechanical characteristics of reduced-scale model materials with those of the prototype and to provide the information on the best selection of materials. Manufacturing techniques on the micro-concrete and reduced reinforcement are introduced. The test results of these materials are shown to be satisfactory with regard to the similitude requirement. The simple beam tests were performed to verify similitude in the bond behavior between micro-concrete and reduced reinforcement. Those results also prove that these manufacturing and experimental techniques are useful and reliable for reduced-scale model tests.

• The Journal of Korean Academy of Prosthodontics
• /
• v.28 no.2
• /
• pp.53-76
• /
• 1990

The purpose of this study was to evaluate the tensile bond strength of adhesive resins to successively recast Rexillium III and Degudent-U. Recasting was done 4times successively. Specimen $A_1$, were cast by new metal, and $A_2$ by surpus of $A_1$, $A_3$ by surplus of, $A_2$ $A_4$ by surplus of $A_3$, $A_5$ by surplus of $A_4$ plus 50% new metal. The types of surface treatment for resinbonded restoration in this experiment were electrolytic etching by OXY-ETCH(Oxy dental products, Inc., Hillside, New Jersey, U.S,A.), aluminum oxide blasting, anodic oxidation by EZ-OXISOR( Towagiken Co., Kyoto, Japan), electrotinplating by Kura Ace(Kuralay Co., Kyoto, Japan). Three kinds of cementing resin used in this study were Comspan(K.P. Cauil Co, Milford Delaware, U.S.A.), Super Bond C&B(Sun-Medical Co. Ltd., Kyoto,Japan), Panavia EX(Kuralay Co., Ltd., Osaka, Japan). Tensile bond strength was measured by Instron Universal testing machineModel 1125) and all the specimen were observed with SEM(JEOL, JSM-T2000) and mode of bond failure were recorded. The obtained results were as follows : 1. In electrolytic etched group, tensile bond strength was decreassed when recast alloy was used, and tensile bond strength of Compan and panavia EX were not significantly different(P>0.05). 2. In remaining group treated by aluminum oxide blasting, EZ-OXIOR, Kura Ace, tensile bond strength were not changed when recast alloy were used, and tensile bond strength of SuperBond(C&B and Panavia EX were not significantly different(P>0.05). 3. IN SEM evaluation, electrolytic etched group and electrotinplated group exhibited different image when recast alloy was used, and remaining groups treated by aluminum oxide blasting, EZ-OXISOR exhibited the same. 4. IN observation of bond failure, electrolytic etched group exhibited adhesive failure and remaing groups treated by aluminium oxid blasting, EZ-OXISOR, Kura Ace exhibited adhesive and cohesive failure.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.33 no.3
• /
• pp.153-158
• /
• 2020

In this study, a numerical approach for evaluating the resisting capacity of a partial concrete-filled steel tube (CFST) column is introduced. By strengthening the plastic hinge part of a traditional reinforced concrete column with a steel tube, a partial CFST shows a similar bending moment capacity as that of a full CFST column but with reduced material cost. To conduct an elaborate numerical analysis of a partial CFST column, an improved bond-slip model is applied to a finite element (FE) model at the interface between the steel tube and in-filled concrete. This numerical model is verified through the results of a double curvature bending-compression test. A parametric study with the proposed numerical model is used to obtain the load moment interaction diagrams for evaluating the resisting capacity based on various dimensions. Finally, the required strengthening length is estimated for each degree of thickness of the steel tube, and the failure mechanism of the partial CFST column based on the dimensions of the steel tube are identified.

• Journal of the Korea Concrete Institute
• /
• v.18 no.1 s.91
• /
• pp.91-100
• /
• 2006

This paper presents an analytical model for evaluation of crack widths in structural concrete members. The model is mathematically derived from the actual bond stress-slip relationships between the reinforcement and the surrounding concrete, and the relationships summarized in CEB-FIP Model Code 1990 are employed in this study together with the assumption of a linear slip distribution along the interface at the stabilized cracking stage. With these, the actual strains of the steel and the concrete are integrated respectively along the embedment length between the adjacent cracks so as to obtain the difference in the axial elongation. The model is applied to the test specimens available in literatures, and the predicted values are shown to be in good agreement with the experimentally measured data.