• Advances in concrete construction
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• v.11 no.5
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• pp.387-396
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• 2021

The behavior of headed bars in concrete is investigated through 108 pullout tests having an embedment depth of eight times the bar diameter in the M20 concrete mix. Headed bars are designed based on ASTM A970-16 and ACI 318-19 recommendations. The primary parameters used in this study are the steel bar diameter, the steel fibers percentage, and the head shapes. Three failure modes namely, Steel, Concrete-Blowout & Pull-Through failure have been observed. Based on load-deflection curves which are plotted to investigate the bond capacity of headed bars, it is observed that the circular-headed bars have displayed the highest peak load. The comparative analysis shows the smaller differences in the ultimate bond strength between MC2010 (0.89-2.26 MPa) and EN 1992-1-1 (2.32 MPa) as compared to ACI-318-19 (11-22 MPa) which is due to the absence of embedment depth and peak load factor in MC2010 and EN 1992-1-1 respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.438-441
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• 2004

This paper presents the results of the experimental study on the performances of reinforced concrete beams rehabilitated by external unbonded high tension steel-bar. Design variables for the experiment in this study includes the position of anchorage zone of the high tension steel bar, the anchorage length of the reinforcing steel bar and the types of the shear strengthening measures. 5 specimens were tested with one point monotonically increased loads and structural performances such as strength capacities, ductility capacities and failure modes were analysed. It is found that the structural performance of the rehabilitated beams are strongly depended on the location of anchorage zone of the high tension steel-bars. In the case that anchorage zone is located near the critical shear zone, it is observed that the rehabilitated beam is failed in brittle failure mode and the additional shear strengthening is necessitated. But if anchorage zone is properly located or additional shear strengthening device is provided properly, it is also observed that the strength capacity of the rehabilitated beams could be increased more than $200\%$ by the proposed method.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.124-127
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• 2004

This study is to investigate the bond characteristics of glass fiber reinforced polymer(GFRP) reinforcing bars in concrete by pullout test experimentally. Three different types of GFRP bars with different surface deformations were considered in this study. Also, standard deformed steel reinforcing bar with or without epoxy-coating were included for the comparisons of bond strength. All test procedures including specimens preparation, test apparatus and measuring devices were made according to the recommendation of CSA(Canadian Standards Association) Standard S806-02. From the test results, it was found that small surface indentations contributed to increase the bond strength of GFRP bar significantly. Based on the limited test results till now, the bond strength of GFRP bar with sand-coated deformation commercially available in foreign market is around $80\%$ of that of steel deformed bars.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.3 s.10
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• pp.143-150
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• 2003

Recently, The corrosions of reinforced concrete structures are severe problems of economical social effects. PE-coated bars protecting from corrosion and enhancing durability of reinforced concrete structures are testified to evaluate structural properties. Tests are verified by comparative bending tests of the three type materials of epoxy coating, without coating and pe-coating. Load-deflection relations ate superior in pe-coated bar than any other materials(bare bar and epoxy bar). These are proved bonding properties enhancement by using cement powder.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.539-544
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• 2000

The purpose of this study is to develop the mechanical anchorage, namely MAB-BOP (Mechanical Anchorage of 90$^{\circ}$ Hooked Bars with BOlt nad Plate) of the beam-column joint in precast concrete framed structures. Six specimens simulating typical interior beam-column joints were tested to investigate the mechanical characteristics of MAB-BOP. Of primary interest was the measurement of the slip of the anchored bar. Th load-slip curve obtained from this test were used to compare the mechanical performances of the different anchoring methods. Based on the test results, it was found that MAB-BOP showed sufficient anchoring strength capacity compared to 90$^{\circ}$ hooked bar method. So, MAB-BOP can be used as the anchoring methods of the reinforcing bars in PC beam-column joint.

• Journal of Industrial Technology
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• v.17
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• pp.145-151
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• 1997

This paper presents evaluation results of the tensile behavior of reinforced high strength concrete. The effects of different sizes of reinforcing bar, ranging from D22 to D29, on the formation of cracks was investigated. Two different strength concretes, $270kg/cm^2$ and $550kg/cm^2$, were used in the specimens to investigate the influence if concrete strength on tension stiffening. In the present investigation a method was developed to obtain reliable load-deformation behavior in tension. The experimental results show that (1)high-strength concrete members exhibited larger amounts of tension stiffening than the companion normal-strength concrete members, (2) as the bar diameter increases, the beneficial influence of high-strength concrete on tension stiffening is reduced.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1045-1050
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• 2001

This study was performed to evaluate reinforced concrete durability in chloride attack environment under sustained load by the corrosion of reinforcing bars and the permeation of chloride ion. Generally, it is regarded that permeability of chloride ion is determined by the properties of concrete, but the effects of load which make alternation of concrete inner structure such as crack and so on should not neglected. In this study, it is shown that the relation between bending load on RC beam, deflection and crack of specimen, permeation of chloride ion, rating of re-bar corrosion, and the relation between compression load and permeation of chloride ion. Therefore the effects of load on permeation of chloride ion and re-bar corrosion are evaluated.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.402-405
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• 2006

Inner support regions of continuous steel and concrete composite bridge decks, transverse crackings are easely developed by tensile forces due to live loads and primary and secondary effects of concrete shrinkage. Since these cracks have an influence on the durability of bridge decks, crack width should be controlled within allowable limit values. Although crack width is a function of steel stress, bar diameter, bar spacing, etc, the current code for the amount of longitudinal reinforcements provides only one value of 2 percent of the concrete area. In order to investigate cracking bahaviors of composite girders with the variation of the longitudinal steel ratios, negative flexural tests are conducted on five composite girders and crack width and crack spacing are compared to ACI Code and Eurocode. Based on the test results, it is discussed the suitability of the current code for the longitudinal steel ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.173-176
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• 2003

Progressive failure analysis of steel composite double T-beam is performed to investigate the mechanical effects of steel composite fabricated in the webs of double-T beam to replace concrete placing forms. The analysis is based on nonlinear finite element scheme considering material nonlinearities of concrete, reinforcing bar and PS steel. Four-parameter strength envelope defines the hardening and softening phenomena of concrete with consideration of the various levels of confining pressures. Rankine maximum strength criterion defines the elasto-plasticity of PS steel and reinforcing bar, and Von Mises $J_2$ failure criterion for steel plate which wraps the concrete webs of double T-beam. A 6m long two-span steel composite double T-beam is analyzed and compared with the experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.204-209
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• 1995

The influence of the interfacial properties on the bond capacity of reinforcing bars to concrete is studied in this paper. In this study, the deterioration of the interfacial bond capacity when top-cast bars or epoxy-coated bars are used is examined. The effect of such variables on bond capacity in reinforced concrete is studied by experiment which use beam-end specimens. The main objective of this study is that comparing the test results and the requirements in ACI 318-89 code. the verification of the factor in ACI code is also presented in this paper. The results of the test show that "top bar effect" is considerably affected by the slump of fresh concrete, so the influence of slump shoud be taken into account for top bar effect factor in code. Test results also shows that the bond-slip curve of the epoxy-caoted bars is similiar to that of the uncoated and bond strength is reduced about 15% and that coating thickness seems to influence the bond strength deterioration.rioration.