• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.399-404
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• 2000

This paper are the mechanical characteristics of eccentrically loaded normal strength and high strength reinforced concrete columns based on the test results. The columns are $120\times120$mmat the mid-section and are haunched at the ends to apply the eccentric loading and prevent premature failure. Variables are concrete strengths(361, 672, 974 kgf/$\textrm{cm}^2$), $\textrm{cm}^2$longitudinal reinforcement ratios (1.98, 3.54, 1 5.53%), spacing of lateral reinforcement (30, 60, 120mm), and eccentricities (24, 40mm). As a results, the main conclusions obtained from the comparison and analysis for the strength tendency, deformation and ductility of high strength reinforced concrete columns with variables are as follows; As the concrete compressive strength concrete and lateral reinforcement increases, the ductility index of high strength reinforced concrete columns decrease, but it increase with the increase of eccentricity and longitudinal reinforcement ratio. The confinement ratio must be greater than 20 percent in order for the level of ductility between high strength reinforced concrete columns and normal strength reinforced concrete columns to be almost equal.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.81-84
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• 2008

The purposes of this study are to verify a reasonable model of material characteristic and to propose a rational model of reinforcement characteristic considering monotonic and cyclic loading about manufactured reinforcing steel in Korea. Longitudinal reinforcements of the plastic hinge region were behaved tensile deformation and compressional deformation by direction of lateral loading. However Confinement steels were behaved only tensile deformation by lateral loading. Transverse steels were laid the state of tension in the lateral loading of time, and they were laid state that stress is zero when it was removed lateral load. The tests for cyclic tension loading were performed for test variable as yield strength and reinforcement bar sizes. It was estimated that the total strain energy per unit volume was 74 $MJ/m^3$. The modified ultimate concrete compression strain model was proposed based on experimental study of cyclic tension test for manufactured reinforcing steel in Korea.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.305-308
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• 2008

The purpose of this study is to propose the confinement effectiveness of precast segmental concrete that binding by lateral confining steel in the method of precast segmental concrete pridge piers construction. Generally, the confinement effect of concrete that binding by lateral confining steel is defined by the confinement effectiveness coefficient and the confinement effectiveness coefficient is defined as the ratio of area of effectively confined concrete core to area of confined concrete core. The area of effectively confined concrete core is defined by Arching action occurred on a space of lateral confinement steel and The area of confined concrete core is defined by the ratio of area of longitudinal reinforcement to area of core of section. But in case of precast segmental concrete, concrete cover that exist on top and bottom of concrete segment should be considered.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.643-650
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• 2012

The limitation of the yield strength in reinforced concrete columns is given for the effective use of high-strength steel bar, because very high-strength steel bar does not yield while concrete fails in compression. In order to overcome this limitation, it is required to increase peak strain of the concrete. The objective of this study is to examine the confinement effect of plate type lateral reinforcement in reinforced concrete columns. From this experimental study, the reinforced concrete columns confined by plate type carbon fiber sheets showed higher compressive strength and peak concrete strain comparing to the unconfined columns. The confinement effect is higher when cross-sectional type is a circular one than a square one. Moreover, the confinement effect was also higher for circular type confinement. Based on this study, high-strength steel bars with strength exceeding 800 MPa can be effectively used for reinforced concrete columns confined by plate type lateral reinforcements.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.578-588
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• 2002

An experimental study was conducted to investigate the effectiveness of transverse reinforcement in reinforced concrete tied columns subjected to monotonically increasing axial compression. Eighteen large-scale columns(260$\times$260$\times$1200 mm) were tested. Effects of main variables such as the concrete compressive strength, the tie configuration, the transverse reinforcement ratio, the tie spacing, and the spatting of the concrete cover were considered. High-strength concrete columns under concentric axial loads show extremely brittle behavior unless the columns are confined with transverse reinforcement that can provide sufficiently high lateral confinement pressure There is a consistent decrease in deformability of column specimen with increasing concrete strength. Test results were compared with the previous confinement model such as modified Kent-Park, Sheikh-Uzumeri, Mander, and Saatcioglu-Razvi model. The comparison indicates that many previous models for confined concrete overestimate or underestimate the ductility of confined concrete.

• Journal of Korean Society of Steel Construction
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• v.22 no.5
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• pp.497-509
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• 2010

Five concrete-encased steel columns using high-strength steel($f_{ys}$=801MPa) and high-strength concrete($f_{ck}$=97.7MPa) were tested to investigate the eccentric axial load-displacement relationship. Test parameters included the type, yield strength, and spacing of lateral reinforcement, and also the eccentricity of axial load. To analyze the behavior of the column specimens, the nonlinear sectional analysis using strain-compatibility and confinement effect was performed. To examine the applicability of existing design codes for the composite sections using high-strength materials, the test results were also compared with the predictions by the nonlinear analysis and the design codes. The confinement effect of lateral reinforcement increased the ductility of concrete, and the moment capacity of the column specimens increased with the ductility of concrete. The prediction by the nonlinear analysis gave good agreement with the test results. On the other hand, the ACI 318 neglecting lateral confinement effect underestimated the strength of the column specimens, and the Eurocode 4 using complete plastic capacity of steel section overestimated.

• International Journal of Concrete Structures and Materials
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• v.18 no.2E
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• pp.133-142
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• 2006

An experimental study was conducted to investigate the effectiveness of transverse steel in reinforced concrete tied columns subjected to monotonically increasing axial compression. Eighteen large-scale columns($260{\times}260{\times}1,200mm$) were tested. Effects of such main variables as concrete compressive strength, configurations of transverse steel, transverse reinforcement ratio, spacing of transverse steel, and spalling of concrete cover were investigated. High-strength concrete columns under concentric axial loads show extremely brittle behavior unless the columns are confined with transverse steel that can provide sufficiently high lateral confinement pressure. A consistent decrease in the deformability of the column test specimens was observed with increasing concrete strength. Test results of this study were compared with existing confinement models of modified Kent-Park, Sheikh-Uzumeri, Mander, and Saatcioglu-Razvi. The comparison indicates many existing models to predict the behavior of confined concrete overestimate or underestimate the ductility of confined concrete.

• Computers and Concrete
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• v.34 no.5
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• pp.611-623
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• 2024

Concrete shear walls have a wide range of applications as one of the primary lateral load-bearing elements in the construction industry. Implementation constraints often lead to the use of lap-spliced Rebar for these walls. The presence of lap-splice allows for longitudinal reinforcement slippage in the lap-spliced region, which, if it occurs, can result in reduced ductility and undesirable seismic performance of the wall. To further investigate this matter, 32 wall models with variations in longitudinal reinforcement diameter, lap-splice length, percentage of transverse reinforcement, and debonded rebar were numerically and analytically studied using finite element analysis. The selected models were subjected to gravity and cyclic lateral loads, considering bond strength and slippage in the lap-spliced region. By comparing the obtained results, including hysteresis curves, ductility, energy dissipation, reinforcement strain, and crack propagation, with continues rebars wall, it was demonstrated that the presence of lap-spliced Rebar for longitudinal reinforcement causes slippage in the lap-spliced region and reduces the structural ductility. Additionally, the results showed that in walls with lap-spliced Rebar, the use of debonding method compensates for the weakness caused by reinforcement slippage, leading to the restoration of ductility and improvement in seismic performance of the wall while ensuring resistance.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.463-466
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• 1999

Ductility is an important consideration in the design of reinforced high-strength concrete. Therefore, this research investigate the ductile behavior of rectangular high-strength concrete columns like as bridge piers with confinement steel. The effect on the ductility of axial load, lateral reinforcement ratio, longitudinal reinforcement ratio, shear ratio, and compressive strength of concrete were investigated analytically using layered section analysis. As the results, it was proposed the proper relationship between ductility and variables and formulated into equations.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.89-92
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• 2006

In order to achieve target ductility the stress-strain relation of confined concrete is indispensible. In this study the specimens with different transverse reinforcement ratios were tested. The test results were compared with empirical equations and the characteristics of confinement effect were investigated.