• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.287-297
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• 2015

In concrete structural design provisons, there is a minimum allowable strain of steel to ensure a ductility of RC members and a c/d is limited for the same purpose in EC2. In general, a ductility capacity of RC members is evaluated by a displacement ductility which is a ratio of ultimate displacement to yield displacement, and it is necessary to calculate accurately a yield displacement and an ultimate displacement to evaluate a displacement ductility. But a displacement in members is affected by various member characteristics, so it is hard to calculate a displacement exactly. In this study, a displacement ductility is calculated by calculating a yield displacement and an ultimate displacement through a moment-curvature relationship. The main variables examined are concrete strength, yield strength, steel ratio, spacing of confinement, axial force ratio and concrete ultimate strain. As results, as a concrete strength is increased, a ductility displacement is increased. But as yield strength, steel ratio, spacing of confinement and axial force ratio are increased, a displacement ductility is decreased. And a displacement ductility is necessary to calculate a response modification factor (R) of columns for seismic design, so it is appeared that it is important to calculate a displacement ductility more accurately.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.1-12
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• 2013

This study presents the evaluations of seismic performance and displacement ductility for two types of RC columns: existing RC column without SFM (Super Flexibility Membrane) and CSF (RC columns strengthened with SFM). After they are analyzed by the experiment as well as FEM, crack patterns and load-displacement curve of CSF by the former are shown to similar to those of CSF by the latter. The flexural cracks are dominant in CSF, whereas shear cracks in CNF (existing RC column without SFM). Displacement ductility of CSF is shown significantly to increase as well as ultimate displacement, compared to those of CNF. Therefore CSF can be replaced to CNF in order to increase the seismic performance and displacement ductility.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.51-61
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• 2003

This research is a park of a research program to develope a new design method for reinforced concrete bridge columns under axial load and cyclic lateral load. The objectives of this paper are to investigate the relationship between curvature ductility and displacement ductility and to propose a correlation equation for designing of reinforced concrete bridge columns under axial load and cyclic lateral load. Computer program NARCC was used for parametric study, which was proved to provide good and conservative analytical result especially for deformation capacity and ductility factor compared with test result. A total of 7,200 spirally reinforced concrete columns were selected considering the main variables such as section diameter, aspect ratio, concrete strength, yielding strength of longitudinal and confinement steel, longitudinal steel ratio, axial load ratio, and confinement steel ratio. A new equation between curvature ductility factor displacement ductility factor with the aspect ratio was proposed by investigation of 21,600 data produced from the selected column models by applying 3 different definitions of yield displacement.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.193-202
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• 2008

Seismic design for bridge columns of the current Korea Highway Bridge Design Specifications which adopt full ductility design concept results in reinforcement congestion problems in construction site. It is due to large amount of confining steel is required even for small ductility demand which is a normal case in low and moderate seismicity regions like Korean peninsular. Therefore a new seismic design method based on limited ductility concept was proposed, which is called ductility demand based design method. It uses the new confining steel design equation considering ductility demand and aspect ratio of the column as well as material strength. The purpose of this study is to verify safety of the ductility demand based design method by the confining steel design equation. Eighty nine circular column test results are selected and investigated in terms of ductility factor and its safety. The safety factor for the circular column test results ranges between 1.11 and 3.98, and the average is 1.90. In this paper, the basic concept and detailed design procedure of the ductility demand based design method are also introduced as well as the investigation of the safety with respect to the major variables in confining steel design.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.3
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• pp.11-21
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• 2002

The evaluation of displacement ductility is performed by direct method through tracking the inelastic hysteretic behavior of RC bridge columns subject to cyclic loading using a flexibility-based fiber element mode. To reasonably track the inelastic behavior until the RC bridge column reaches its ultimate state, the average stress-average strain relations and joint elements, which agree well with experiments, are modified and applied considering the tension stiffening behavior and discontinuous displacement between the column and its base. In addition the evaluation of displacement ductility is performed by a direct method easily applicable to numerical analysis. Locations for the integration points, values for the post-crushing concrete strength and low-cycle fatigue failure of longitudinal reinforcement that affect the calculation of yielding and ultimate displacements are proposed for the application to flexibility-based fiber element model. Since less than 10% of error occurs during the displacement ductility analysis, the yielding and ultimate displacements evaluated by the applied analysis method and model appear to be valid.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.3 s.43
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• pp.69-75
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• 2005

In this paper, the comparative performance of repaired RC columns using steel and CFRP is presented. Also, the effect of transverse reinforcement ratio on the behavior of the steel and the CFRP repairing is investigated. Monotonic and cyclic load tests are conducted on nine RC column specimens with different repairing strategies and transverse reinforcement ratios to compare the load-displacement curves and the hysteretic behaviors. From the tests, it is observed that both steel and CFRP jacket repairings can significantly increase the displacement ductility and the ultimate load capacity of damaged columns.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.2
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• pp.37-47
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• 2010

In order to attain enhanced seismic performance of RC bridges, premature shear failure prior to the achievement of target ductilities of the piers should be prevented. For this purpose, a reliable shear strength evaluation is required. The shear strength of an RC column subjected to a lateral force decreases with an increase in ductility. Many empirical equations for the shear strength have been proposed by many researchers. However, there are many discrepancies in the initial shear strength in the low ductility range, and in the decrease rate according to the ductility. In this study, a new empirical equation of shear strength considering the displacement ductility effect has been proposed, in which the initial shear strength equation proposed by the authors was revised on the basis of the investigation of many other researchers' test results. The resulting improvement in accuracy is confirmed by comparison with other empirical equations.

• Journal of Korean Association for Spatial Structures
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• v.12 no.3
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• pp.63-70
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• 2012

In this study, the displacement-based design concept, the performance by the existing reinforced concerte column and steel reinforced concrete composite column for SRC purchased the maximum design ground acceleration improvement compared to the performance design. SRC have several advantages such as strength enhancement and high ductility. H-beam or steel tubes were used for embedded elements of the SRC composite columns. SRC cross-section for the P-M diagram and analysis on the nominal bending monent SRC designed for composite columns for disparity estimation is presented to the displacement-based seismic design. Performance improvement of the performance-based design performance targets for the design seismic displacement and design criteria for the direct displacement-based design methods and to improve the seismic performance due to the displacement coefficient method is proposed to design. SRC compared with the RC column designed to improve the performance and displacement ductility ratio displacement results in the performance design results showed significantly improved performance.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.39-48
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• 2003

This paper present a summary of the results of statistical study of the ductility factor which is key component of response modification factor(R). To compute the ductility factor, a group of 1,860 ground motions recorded from various earthquake was considered. Based on the local site conditions at the recording station, ground motions were classified into four groups according to average shear wave velocity. Inleastic spectrum were computed for elastic perfectly plastic SDOF systems undergoing different level of inelastic deformation and period. Ductility factors were calculated by deviding elastic response spectrum by inelastic response spectrum. The influence f displacement ductility ratio, site condition, magnitude and epicentral distance on ductility factors were studied. The coefficient of variation was computed to evaluated the dispersion of ductility factors as the defined ratio of the standard deviation to the mean.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.2
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• pp.29-37
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• 2002

The purpose of this study is to provide a fundamental data of earthquake resistant design through the estimation of the response modification factor and nonlinear displacement for moment resisting reinforced concrete frames by linear and nonlinear static analysis. The analysis models are designed in accordance with AIK code and then, estimated the response modification factor and nonlinear displacement of the buildings. The parameters such as story numbers(10, 20, 30), plan ratios(1:1, 1:2) and analysis types(2D, 3D) of building structure are chosen for use in this study. After comparing the results of linear and nonlinear static analysis, the response modification factor is obtained as the product of four factors: ductility factor, strength factor, damping factor and redundancy factor. The response modification factor are close to 3.5 in case of 2 span, 4.3 in case of 3 span and 5.0 in case 4 or more span models regardless number of stories and plan ratios. The nonlinear displacement is evaluated from the ratio of story drift angle(nonlinear drift/linear drift). The ratio of story drift angle increases as story numbers increase and the value varies from 5.85 to 9.34.