• Title/Summary/Keyword: Concrete confinement

Search Result 652, Processing Time 0.023 seconds

Confinement Effects of High-Strength Reinforced Concrete Tied Columns

  • Han, Byum-Seok;Shin, Sung-Woo
    • International Journal of Concrete Structures and Materials
    • /
    • v.18 no.2E
    • /
    • pp.133-142
    • /
    • 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.

Shear Strenhth and Ductility of Steel-Fiber Reinforced High Strength Concrete Beams with Shear Confinement (전단보강이 있는 강섬유 보강 고강도 철근콘크리트 보의 전단 및 연상에 관한 연구)

  • 오정근;이광수;권영호;신성우
    • Magazine of the Korea Concrete Institute
    • /
    • v.2 no.4
    • /
    • pp.53-60
    • /
    • 1990
  • Investigations on the behavior of steel fiber reinforced high strength concrete beams with shear confinement are accomplished to determine their ultimate shear strength including diagonal tension strength. The parameters varied were the shear confinement ratio(Ps), and fiber volume fraction(Vs). Ultimate shear strength increased significantly in steel fiber reinforced concrete beam without shear confinement. In steel- fiber reinforced high strength concrete beams with shear confinement, there is no increase of ultimate shear strength but shows much beneficial effects of Ductility Capacity.

Axial behavior of steel-jacketed concrete columns

  • Rupp, J.;Sezen, H.;Chaturvedi, S.
    • Steel and Composite Structures
    • /
    • v.16 no.1
    • /
    • pp.59-75
    • /
    • 2014
  • A new concrete confinement model is developed to predict the axial load versus displacement behavior of circular columns under concentric axial load. The new confinement model is proposed for concrete filled steel tube columns as well as circular reinforced concrete columns with steel tube jacketing. Existing confinement models were evaluated and improved using available experimental data from different sets of columns tested under similar loading conditions. The proposed model is based on commonly used confinement models with an emphasis on modifying the effective confining pressure coefficient utilizing the strength of the unconfined concrete and the steel tube, the length of the column, and the thickness of the steel tube. The proposed model predicts the ultimate axial strength and the corresponding strain with an acceptable degree of accuracy while also highlighting the importance of the manner in which the steel tube is used.

A study on compressive strength of concrete in flexural regions of reinforced concrete beams using finite element analysis

  • Cho, Chang-Geun;Hotta, Hisato
    • Structural Engineering and Mechanics
    • /
    • v.13 no.3
    • /
    • pp.313-328
    • /
    • 2002
  • Based on the orthotropic hypoelasticity formulation, a triaxial constitutive model of concrete is proposed. To account for increasing ductility in high confinement of concrete, the ductility enhancement is considered using so called the strain enhancement factor. It is also developed a three-dimensional finite element model for reinforced concrete structural members based on the proposed constitutive law of concrete with the smeared crack approach. The concrete confinement effects due to the beam-column joint are investigated through numerical examples for simple beam and structural beam member. Concrete at compression fibers in the vicinity of beam-column joint behaves dominant not only by the uniaxial compressive state but also by the biaxial and triaxial compressive states. For the reason of the severe confinement of concrete in the beam-column joint, the flexural critical cross-section is observed at a small distance away from the beam-column joint. These observations should be utilized for the economic design when the concrete structural members are subjected to high confinement due to the influence of beam-column joint.

Aseismatic Retrofit of Concrete Piers with Restraining Steel Ring and Expansive Concrete (구속강판과 팽창콘크리트를 이용한 기존 RC 교각의 내진 보강)

  • 최익창;박홍용;연준희;김연수
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2001.11a
    • /
    • pp.953-958
    • /
    • 2001
  • A retrofit method “Steel Ring Confinement Retrofit” was proposed and discussed on the material and member characteristics through experiments. Steel Ring Confinement Retrofit consist of confining steel ring and expansive concrete. The steel ring is set on the footing, surrounding the base of the pier. By placing expansive concrete between the pier and steel ring, chemical prestress is introduced in the members. Chemical prestressed ring concrete enlarge the pier section and enhance both the strength and ductility of the pier. It was confirmed that Various Ring Confinement Retrofit improved the strength of the pier up to 30% ~ 100% with experiments.

  • PDF

Confinement Effects of Concrete by GFRP Shells (GFRP Laminates에 의한 콘크리트의 구속)

  • 조순호;선성규;정창원;조규성
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2003.05a
    • /
    • pp.937-942
    • /
    • 2003
  • Three series of 36 short circular columns confined by wraps, full shells and partial shells were tested by varying the thickness of GFRP laminates. An assessment of the effectiveness of the existing models on confinement of concrete columns with FRP was made for present tests. Test results indicated significant increases in strength and deformability compared with those in unconfined concrete, particularly warp and full shell confinement. Existing predictive equations for peak strength and strain of confined concrete showed a large scatter and varied considerably, resulting from the realistic fracture strains of FRP nor considered.

  • PDF

Compressive Strength Enhancement of Concrete Cylinders Confined with FRP Wrapping (FRP로 횡보강된 콘크리트 공시체의 압축강도 향상에 관한 연구)

  • 김영섭;정영수;박창규;송희원
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2003.11a
    • /
    • pp.351-354
    • /
    • 2003
  • Triaxial behavior of concrete cylinders wrapped with FRP material has been investigated for the increase of concrete strength by lateral confinement. Using the model by Richart et al., a modified empirical equation was proposed to estimate the strength of concrete cylinders with FRP confinement based on the linear relationship between the concrete strength and lateral confining pressure. From the experimental stress-strain result of the cylinder specimens having similar confining pressure, less ductility was observed for higher strength concrete. But the compressive strength of the specimen was linearly increased by lateral confinement. The confinement effectiveness coefficient for the strength enhancement of the cylinders by FRP wrap was obtained as 2.27 from the regression analysis.

  • PDF

Effect of Edge Confinement on Deformation Capacity in the Isolated R/C Structural Walls (전단벽의 단부보강효과에 따른 변형능력의 평가)

  • 이희동;한상환;이리형
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 1998.10a
    • /
    • pp.525-528
    • /
    • 1998
  • This paper reports on tests of reinforced concrete shear walls for wall-type apartment structure under axial loads and the cyclic reversal of lateral loads with different confinement of the boundary elements. Confinement of the extreme element by U-stirrups and tie hooks seems to be as effective as closed stirrups. The shear strength capacity seems not to be increased by the confinement but deformation capacity improved.

  • PDF

Nonlinear Analysis considered Confinement Effect of Precast Concrete Segment (프리캐스트 콘크리트 세그먼트의 구속효과를 고려한 비선형 해석)

  • Lee, Heon-Min;Kim, Tae-Hoon;Park, Jae-Keun;Kim, Young-Jin;Shin, Hyun-Mock
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2008.04a
    • /
    • pp.305-308
    • /
    • 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.

  • PDF

Effect of shape and amount of transverse reinforcement on lateral confinement of normal-strength concrete columns

  • Kim, Hyeong-Gook;Kim, Kil-Hee
    • Advances in concrete construction
    • /
    • v.14 no.2
    • /
    • pp.79-92
    • /
    • 2022
  • The amount and configuration of transverse reinforcement are known as critical parameters that significantly affect the lateral confinement of concrete, the ductility capacity, and the plastic hinge length of RC columns. Based on test results, this study investigated the effect of the three variables on structural indexes such as neutral axis depth, lateral expansion of concrete, and ductility capacity. Five reinforced concrete column specimens were tested under cyclic flexure and shear while simultaneously subjected to a constant axial load. The columns were reinforced by two types of reinforcing steel: rectangular hoops and spiral type reinforcing bars. The variables in the test program were the shape, diameter, and yield strength of transverse reinforcement. The interactive influence of the amount of transverse reinforcement on the structural indexes was evaluated. Test results showed that when amounts of transverse reinforcement were similar, and yield strength of transverse reinforcement was 600 MPa or less, the neutral axis depth of a column with spiral type reinforcing bars was reduced by 28% compared with that of a column reinforced by existing rectangular hoops at peak strength. While the diagonal elements of spiral-type reinforcing bars significantly contributed to the lateral confinement of concrete, the strain of diagonal elements decreased with increases of their yield strength. It was confirmed that shapes of transverse reinforcement significantly affected the lateral confinement of concrete adjacent to plastic hinges. Transverse reinforcement with a yield strength exceeding 600 MPa, however, increased the neutral axis depth of normal-strength concrete columns at peak strength, resulting in reductions in ductility and energy dissipation capacity.