• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.493-494
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• 2009

Two strengthened columns and an unstrengthened control column were tested to failure under cyclic lateral load combined with a constant axial load to effect of anchorage of T-shaped steel plate in the strengthened column using wire rope units. Main variables considered were anchorage method of T-shaped steel plate. Tested columns were compared with those of conventionally tied columns tested by research of before. Test results showed that lateral load capacity and the displacement ductility ratio of anchorage of T-shaped steel plate in the strengthened column increased 40% and 130% than unstrengthened column, respectively. In particular, at the same effective lateral reinforcement index, a much ductility ratio was observed in the strengthened columns than in the tied columns.

• KIEAE Journal
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• v.7 no.4
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• pp.105-111
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• 2007

As this study investigates the influence about type of transverse reinforcement, spacing of transverse reinforcement(s), volumetric ratios of transverse reinforcement(${\rho}s$) of ultra-high strength concrete columns. It try to offer to resonable basic data of the confined model for the ultra-high concrete of in reinforced concrete columns. Experimental tests with large scaled columns were conducted under concentric axial loads. The ultra-high strength concrete (100MPa) was used. From this test result, it evaluate influence of the strength enhancement and ductility enhancement, important variables about behavior of the confined concrete by confinement of ultra-high strength reinforced concrete.There are two ways to improve the confinement effect of high strength concrete columns through the increase of amounts and/or strength of transverse reinforcement.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.603-608
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• 1997

Studies on the second-order analysis of reinforced concrete columns have been chiefly dealt with symmetric section under uniaxial loading. In practical situations, however, columns are subjected to biaxial loadings. Therefore, for more accurate prediction of the behavior of concrete columns under biaxial loading, the interaction between bending moments of major and minor axes should be considered. Recently Kim & Lee proposed a numerical method of predicting the behavior of concrete columns under biaxial loading. In this paper, to investigate the behavior of concrete columns under biaxial loading and verify the validity of proposed method, a series of test were carried out for sixteen tied reinforced columns with 100${\times}$100mm square and 200${\times}$100mm rectangular sections under various loading conditions. The length of columns was 1,300mm and the concrete strength was 28MPa. The boundary conditions at the both ends were hinged and end eccentricities were equal(400mm). Proposed numerical analyses applied to the test piece were performed to predict behavior of concrete columns with square and rectangular sections under various loading conditions. Test results were also compared with those using the moment magnifier method in ACI code. The test results showed that the moment magnifier method is conservative.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.369-374
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• 2000

This study was conducted to investigate the seismic behavior assessment of circlular-tied bridge piers, particularly with regard to assessing the displacement ductility. The experimental variables of bridge piers test consisted of transverse steel details, amount and spacing different axial load levels etc. The test results indicated that reinforcement concrete bridge piers with confinement steel by the code specification exhibited sufficient ductile behavior and seismic performance. Aldo, it is found that current seismic design code specification of confinement steel requirements may be revised.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.743-749
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• 1999

Recently new rehabilitation techniques have been proposed with advanced composite materials like carbon fiber, aramid, glass fiber sheet and so forth. The purpose of this paper is to investigate the mechanical characteristics of reinforced concrete columns confined with carbon fiber sheet and evaluate the degree of their strengthening effect. For the test, the specimen size of column is 15cm$\times$15cm$\times$90cm reinforced with 4 number of main bars of 10 mm diameter, tied bars of 6 mm diameter and slenderness ratio 20. Columns were wrapped with carbon fiber sheet along the column length. It is necessary to make some assumption regarding the confinement of carbon fiber sheet to apply to reinforced concrete columns under concentric loads. The strength gain effect of columns confined with carbon fiber sheet could be predicted using the proposed equation.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.284-292
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• 1995

This paper is on experimental study on the behavior of reinforced concrete columns subjected to longitudinal steel ratio To investigate the effects of concrete strength and longitedinal steel ratio on the behavior of reinforced concrete columns. a series of tests were carried out for thirty-six tied reinforced concrete columns with a 100mm square cross section and three slendemess ratio of 15, 30 and 50. And To study and illustrate the change of the ultimate loads and that of displacements, two different concrete strength of 180,26kfg/$\textrm{cm}^2$, 819,36kfg/$\textrm{cm}^2$ and five different longitudinal steel ratio of 0.5, 1.0, 4.0, 5.7 and 10.3% were used. The boundary conditions at the ends were both hinged and the end eccentricities (17mm) were equal and of the same sign. While the ultimate load capacity of high-strength concrete column was much increased when the columns were short, that was not when the columns were slender. The effect of longitudinal steel ratio on the increased of ultimate load of column was more evident for slender columns than for short ones and the ultimate of longitudinal steel ratio were more pronounced with increasing concrete strength. The more inserted the longitudinal steel, the more increased the ultimate load, but the superabundance of longitudinal steel ratio over the limitation of maximum steel ratio in ACI code was used, it was showed that the ultimate load was rather decreased.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.161-168
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• 2006

An experimental investigation was conducted to examine the hysteretic behaviors of ultra-high strength concrete tied columns. The purpose of this study is to investigate the safety of ultra-high strength concrete columns with 100 MPa compressive strength for the requirement of ACI provisions. Eight 1/3 scaled columns were fabricated to simulate an 1/2 story of actual structural members with the cross section $300{\times}300mm$ and the aspect ratio 4. The main variables are axial load ratio, configurations and volumetric ratios of transverse reinforcement. The results show that the deformability of columns are affected by the configurations and volumetric ratios of transverse reinforcement. Especially, it has been found that the behavior of columns are affected by axial load ratio rather than the amounts and the configurations of transverse reinforcement. Consequently, to secure the ductile behavior of 100 MPa ultra-high strength concrete columns, ACI provisions for the requirement of transverse steel may considered axial load level and the details of transverse reinforcement.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.571-576
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• 1998

This paper is a part of a research plan aimed at the verification of basic design rules of high-strength concrete columns. A total of 19 slender column specimens were tested to measure secondary moment and stiffness of eccentrically loaded reinforced concrete tied columns. Main variables included in this test program were concrete compressive strength, steel amount, eccentricity, and slenderness ratio. The concrete compressive strength varied from 356kg/$\textrm{cm}^2$ to 951kg/$\textrm{cm}^2$, the longitudinal steel ratios were between 1.13% and 5.51%, and slenderness ratios were 40 and 61. Calculated moment magnification factors and column stiffness based on design codes are higher than the test results for high axial load under small eccentricity, for higher slenderness ratio, for lower longitudinal steel ratio, and for high-strength concrete. The moment magnification method of the current design codes may provide a very conservative design for high-strength concrete slender column.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.311-318
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• 2009

An experimental investigation was conducted to examine the hysteretic behaviors of ultra-high strength concrete tied columns. The purpose of this study is to propose the volumetric ratio of transverse reinforcement for ultra-high strength concrete tied columns with 100 MPa compressive strength. Nineteen 1/3 scaled columns were fabricated to simulate an 1/2 story of actual structural members with the main variables of axial load ratio, configurations and volumetric ratios of transverse reinforcement. The results show that the deformability of columns are affected by the configurations and volumetric ratios of transverse reinforcement. Especially, it has been found that the behavior of columns are affected by axial load ratio rather than the amounts and the configurations of transverse reinforcement. To improve the ductility behavior of RC column using ultra high strength concrete in a seismic region, We suggested the amount of transverse reinforcement for all data that satisfy the required displacement ductility ratio over 4. It is means that the lateral confining reduction factor (${\lambda}^c$) considering the effective legs, configuration and spacing of transverse reinforcement and axial load ratio was reflected for the volumetric ratio of transverse reinforcement.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.529-532
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• 1999

With increasing use of high-strength concrete tied columns in structural engineering, it becomes necessary to examine the applicability of related sections of the current design codes. This experimental study was conducted to investigate the behavior of eccentrically loaded high-strength concrete columns. Column specimens with concrete strength 234, 437, 703kgf/㎠ were tested under monotonically increasing eccentric compression. The test parameters included the longitudinal reinforcement ratio, eccentric distance and concrete compressive strength. The analytical results obtained from the stress-strain relationship and the ACI's equivalent rectangular stress block are compared with experimental test results.