• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.239-251
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• 2022

The use of lateral reinforcement in confined concrete columns can improve bearing capacity and deformability. The lateral responses of lateral reinforcement significantly influence the effective confining pressure on core concrete. However, lateral strain-axial strain model of concrete columns confined by lateral reinforcement has not received enough attention. In this paper, based on experimental results of 85 concrete columns confined by lateral reinforcement under axial compression, the effect of unconfined concrete compressive strength, volumetric ratio, lateral reinforcement yield strength, and confinement type on lateral strain-axial strain curves was investigated. Through parameter analysis, it indicated that with the same level of axial strain, the lateral strain slightly increased with the increase in the unconfined concrete compressive strength, but decreased with the increase in volumetric ratio significantly. The lateral reinforcement yield strength had slight influence on lateral strain-axial strain curves. At the same level of lateral strain, the axial strain of specimen with spiral was larger than that of specimen with stirrup. Furthermore, a lateral strain-axial strain model for concrete columns confined by lateral reinforcement under axial compression was proposed by introducing the effects of unconfined concrete compressive strength, volumetric ratio, confinement type and effective confining pressure, which showed good agreement with the experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.363-368
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• 2000

The Korean Bridge Design Standard Specifications adopted the seismic design requirements in 1992. However, The current seismic design requirements for bridges are based on the USA seismic codes for sever earthquake. This provides the basic factors that affects the performance of spiral reinforced concrete piers for seismic loading, and The specimen tests are performed based on load-displacement, effective stiffness and displacement ductility, etc. The quasi-static test was adopted in order to investigate seismic performance of the spiral reinforced concrete pier specimens which had different transverse steel amount, spacing and longitudinal steel ratio under different axial load levels. This study is concluded that seismic design for transverse reinforcement content of spiral reinforced concrete column has influenced on axial load and effective stiffness etc.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.553-558
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• 2001

Recent destructive seismic events demonstrated the importance of mitigating human casualties and serious property damages in design and construction of structures. The Korean Bridge Design Specifications (1992) adopted seismic design requirements based on the AASHTO specification, and minor modification was made in 2000. The longitudinal steel connection of reinforced concrete bridge column is sometimes practically unavoidable. The longitudinal reinforcement details affect seismic performance such as flexural failure and shear failure. This research aims to develop longitudinal steel connection details with confinement steel by experimental study for seismic performance of reinforced concrete bridge columns. Quasi-static test under three different axial load levels was conducted for 12 spiral column specimens. All the column specimens had the same aspect ratio of 3.5. The column specimens were transversely reinforced with spiral and with five different longitudinal steel connection. The final objective of this study is to suggest appropriate longitudinal reinforcement connection details for the limited ductility design concept and improve construction quality.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.345-352
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• 2001

Recent destructive seismic events demonstrated the importance of mitigating human casualties and serious property damages in design and construction of structures. The Korean Bridge Design Specifications (1992) adopted seismic design requirements based on the AASHTO specification, and minor modification was made in 2000. The longitudinal steel connection of reinforced concrete bridge column is sometimes practically unavoidable. The longitudinal reinforcement details affect seisimc performance such as flexural failure and shear failure. This research aims to develop longitudinal steel connection details with confinement steel by experimental study for seismic performance of reinforced concrete bridge columns. Quasi-static test under three different axial load levels was conducted for 12 spiral column specimens. All the column specimens had the same aspect ratio of 3.5. The column specimens were transversely reinforced with spiral and with five different longitudinal steel connection. The final objective of this study is to suggest appropriate longitudinal reinforcement connection details for the limited ductility design concept and improve construction quality.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.657-662
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• 2000

This paper presents the results from experimental study that investigated to explore the load transfer characteristics of post-tensioning anchorage zones. The experimental program investigated the primary variables which affect the ultimate load, lateral strains and crack width: concrete compressive strength, details of reinforcement and shape of anchorage. Through this research, it was found that the governing factor of the ultimate load was not compressive cylinder strength but tensile splitting strength. Ultimate load was increased and lateral strain was decreased as the ratio of spiral increased because the lateral expansion of th concrete inside the spiral was restrained by the spiral. Furthermore, the shape of anchorage which can diminish the wedge effect of anchorage and disperse the anchorage force in various depths was more effective.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.2 s.9
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• pp.127-137
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• 2003

In locations where the cost of concrete is relatively high, or in situations where the weight of concrete members is to be kept to a minimum, it may be economical to use hollow R.C. members. The ductility of circular hollow R.C. columns with one layer of longitudinal and spiral reinforcement placed near the outside face of the section and the steel tube placed on the inside face of the section is investigated. Such hollow sections are confined through the wall thickness since the steel tube is placed. In this study, moment-curvature analyses are conducted with Mander's confined concrete stress-strain relationship. The variables influenced on the ultimate strain is the ratio and yield strength of confining reinforcement and the compression strength for confined concrete. From this ultimate strain - the transverse reinforcement ratio relationship, the transverse reinforcement ratio for circular hollow reinforced columns with confinement is proposed. The proposed transverse reinforcement ratio is confirmed by experimental results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.102-111
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• 2022

The aim of this study is to assess the seismic performance of octagonal hollow cross section reinforced concrete bridge pier, and to investigate the effect of longitudinal reinforcement ratios on the failure behavior. Four octagonal hollow section RC bridge columns of small scale model were tested under a quasi-static cyclically reversed horizontal load with constant axial load. The volumetric ratio of transverse spiral hoop of all specimens was maintained constant(0.206%), the ratios of longitudinal reinforcement were varied(2.36 ~ 4.71%). Failure behavior and seismic performance were investigated. Three specimens with the exception of lap spliced specimen showed flexure-shear failure at final stage. The test results with the exception of lap spliced specimen showed that the displacement ductility factor and accumulated energy dissipation decreased in inverse proportion to the ratio of longitudinal steel.

• Computers and Concrete
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• v.31 no.6
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• pp.527-536
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• 2023

Fiber Reinforced Polymer (FRP) bar has emerged as a viable and sustainable replacement to steel in reinforced concrete (RC) under severe corrosive environment. The behavior of concrete columns reinforced with FRP bars, spirals, and hoops is an ongoing area of research. In this study, 3D nonlinear numerical modelling of circular concrete columns reinforced with Glass Fiber Reinforced Polymer (GFRP) bars and transversely confined with GFRP spirals were conducted using fracture-plastic model. The numerical models and experimental results are found to be in good agreement. The effectiveness of confinement was accessed through von-mises stresses, and it was found that the stresses in the concrete's core are higher with a 30 mm pitch (46 MPa) compared to a 60 mm pitch (36 MPa). The validated models are used to conduct parametric studies. In terms of axial load carrying capacity and member ductility, the effect of concrete strength, spiral pitch, and longitudinal reinforcement ratio are thoroughly investigated. The confinement effect and member ductility of a GFRP RC column increases as the spiral pitch decreases. It is also found that the confinement effect and member ductility decreased with increase in strength of concrete.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.357-366
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• 2010

This paper presents experimental results about shear wall with various lateral reinforcement details in boundary elements. The research objective is to study the structural behavior of shear wall with boundary column confined by rectangular spiral hoops and headed cross ties developed to improve workability in the fabrication of boundary columns. These two details can be fabricated in a factory and put together on-site after being delivered so that the construction work may be reduced. Main parameters in the experimental study were the types of hoop and cross tie: rectangular spiral hoop and headed cross tie vs. standard hoop and cross tie with hook. Four half scaled shear wall specimens with babel shape were made and tested by applying horizontal cyclic load under constant axial force, 10% of nominal compressive strength of concrete. Based on the test result, it was shown that the shear wall with rectangular spiral hoop and headed cross tie in boundary columns has structural capacity compatible with conventional shear wall. The specimen SW-Hh which has bigger hoop bar and higher volumetric ratio of transverse reinforcements than other showed improved energy dissipating characteristic but it presented a rapid reduction of strength after peak point. The results indicates that, it is necessary to consider volumetric ratio of transverse reinforcements as well as hoop space in designing of shear wall with boundary columns for improved strength and ductility.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.589-594
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• 2000

The necessary strength and ductility to avoid structural damage under moderate earthquake can be achieved by properly detailed transverse reinforcement in the plastic hinge zone. However, most structural walls have a higher aspect ratio(M/Vl\ulcorner) without well confined boundary regions. Therefore there is a need for adequate detailing in the plastic hinge zone, particularly boundary regions. In this paper, the fabricated interlocking spirals is introduced as a new seismic detailing for ductile behavior of the structural walls to be able to substitute for existing complicated detailing with ties. This paper also investigates the behavior characteristics of structural walls with interlocking spirals including confinement of the concrete and strength associated with flexure and shear.