• Title, Summary, Keyword: Confinement building

Search Result 61, Processing Time 0.043 seconds

Effects of confinement reinforcement and concrete strength on nonlinear behaviour of RC buildings

  • Yon, Burak;Calayir, Yusuf
    • Computers and Concrete
    • /
    • v.14 no.3
    • /
    • pp.279-297
    • /
    • 2014
  • This paper investigates the effects of confinement reinforcement and concrete strength on nonlinear behaviour of reinforced concrete buildings (RC). For numerical application, an eleven-storey and four bays reinforced concrete frame building is selected. Nonlinear incremental static (pushover) analyses of the building are performed according to various concrete strengths and whether appropriate confinement reinforcement, which defined in Turkish seismic code, exists or not at structural elements. In nonlinear analysis, distributed plastic hinge model is used. As a result of analyses, capacity curves of the frame building and moment-rotation curves at lower end sections of ground floor columns are determined. These results are compared with each other according to concrete strength and whether appropriate confinement reinforcement exists or not, respectively. According to results, it is seen that confinement reinforcement is important factor for increasing of building capacity and decreasing of rotations at structural elements.

Axial capacity of reactive powder concrete filled steel tube columns with two load conditions

  • Wang, Qiuwei;Shi, Qingxuan;Xu, Zhaodong;He, Hanxin
    • Steel and Composite Structures
    • /
    • v.31 no.1
    • /
    • pp.13-25
    • /
    • 2019
  • Reactive powder concrete (RPC) is a type of ultra-high strength concrete that has a relatively high brittleness. However, its ductility can be improved by confinement, and the use of RPC in composite RPC filled steel tube columns has become an important subject of research in recent years. This paper aims to present an experimental study of axial capacity calculation of RPC filled circular steel tube columns. Twenty short columns under axial compression were tested and information on their failure patterns, deformation performance, confinement mechanism and load capacity were presented. The effects of load conditions, diameter-thickness ratio and compressive strength of RPC on the axial behavior were further discussed. The experimental results show that: (1) specimens display drum-shaped failure or shear failure respectively with different confinement coefficients, and the load capacity of most specimens increases after the peak load; (2) the steel tube only provides lateral confinement in the elastic-plastic stage for fully loaded specimens, while the confinement effect from steel tube initials at the set of loading for partially loaded specimens; (3) confinement increases the load capacity of specimens by 3% to 38%, and this increase is more pronounced as the confinement coefficient becomes larger; (4) the residual capacity-to-ultimate capacity ratio is larger than 0.75 for test specimens, thus identifying the composite columns have good ductility. The working mechanism and force model of the composite columns were analyzed, and based on the twin-shear unified strength theory, calculation methods of axial capacity for columns with two load conditions were established.

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.

A Fundamental Study on the Performance of Spalling Resistance of High Performance Concrete with Material of Lateral Confinement Subjected to Fire (화재시 횡구속재 변화에 따른 고성능 콘크리트의 폭열방지성능에 관한 기초적 연구)

  • 배정렬;황인성;홍상희;한민철;한천구
    • Proceedings of the Korean Institute of Building Construction Conference
    • /
    • /
    • pp.47-50
    • /
    • 2002
  • This paper presents the results of fire resistance properties of high performance concrete varying with fiber kinds and the size of metal lath in order to verify the validities of fiber on the spatting resistance by fire. Metal lath, glass fiber and carbon fiber are used to confine the concrete. According to test results, plain concrete without lateral confinement and confined concrete with glass fiber and carbon fiber show entire failure after exposed to fire, while confined concrete with metal lath take place in the form of slight surface spatting by fire, which has favorable spatting resistance of concrete. As for the effect of the size of metal lath, when the size of metal lath is more than 1.2mm of thickness, the residual strength of concrete exposed to fire maintains more than 80% of its original strength. However, glass fiber and carbon fiber does not perform desirable spatting resistance by fire due to loss of lateral confinement of fiber exposed to fire caused by melting of fiber and reducing bond strength between concrete and fiber.

  • PDF

Experimental study on shear capacity of circular concrete filled steel tubes

  • Xiao, Congzhen;Cai, Shaohuai;Chen, Tao;Xu, Chunli
    • Steel and Composite Structures
    • /
    • v.13 no.5
    • /
    • pp.437-449
    • /
    • 2012
  • Concrete filled steel tube (CFST) structures have recently seen wide use in China, but studies of the shear problem of CFST are inadequate. This paper presents an experimental study on the shear capacity of circular concrete filled steel tube (CCFT) specimens with and without axial compression force. Shear capacity, ductility, and damage modes of CCFTs were investigated and compared. Test results revealed the following: 1) CCFTs with a small shear span ratio may fail in shear in a ductile manner; 2) Several factors including section size, material properties, shear span ratio, axial compression ratio, and confinement index affect the shear capacity of CCFTs. Based on test results and analysis, this paper proposes a design formula for the shear capacity of CCFTs.

Field Application of Spalling Prevention Method of High Performance Concrete (고성능 콘크리트의 폭렬방지 공법 현장적용 사례)

  • Kim Kyoung-Min;Heo Young-Sun;Lee Jae-Sam;Jee Suk-Won;Lee Seong-Yeun;Han Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
    • /
    • /
    • pp.7-10
    • /
    • 2005
  • This paper is about manufacture of spalling resistance concrete and also investigates the spalling mechanism and spalling resistance method with diverse materials, mixture proportion and lateral confinement. The present work with the basic experiment achieved successful method for spatting resistance using both proper amounts of fiber contents and lateral confinement using metal lath. Moreover, the developed spatting resistance method was applied for full sized column construction in the Doosan We've Poseidon I field, located in Busan city. The author investigated the physical properties examining workability, placeability and pumpability. These studies are continuously processing to develop new technology expecting remarkable impact on the spatting resistance and fire resistance performance of high-raise building construction in the future.

  • PDF

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.

Evaluation of Structural Capacity of L-shaped Walls with Different Confinement Details Under Web-direction Lateral Force (복부방향 수평하중을 받는 L형 벽체의 횡보강근 구속에 따른 구조성능 평가)

  • 조남선;하상수;최창식;오영훈;이리형
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • /
    • pp.65-70
    • /
    • 2001
  • The compression toe of structural wall is designed to resist the axial compression and shear force caused by wind or earthquake. The performance of shear wall used in tall building is highly influenced by combined shear and axial force. For this reason, it is possible to result in local brittle failure because of concentrated damage in the potential plastic hinge region under severe earthquake. Thus, it is necessary to establish the lateral confinement details at the plastic hinge of shear wall so that shear wall can behave a ductile manner, The objective of this study is to evaluate the seismic performance of L-shaped walls with different confinement details. For this purpose, three wall specimens were tested experimentally and also analyzed using Nonlinear FEM package.

  • PDF

Flexural ductility of RC beam sections at high strain rates

  • Pandey, Akhilesh K.
    • Computers and Concrete
    • /
    • v.12 no.4
    • /
    • pp.537-552
    • /
    • 2013
  • Computation of flexural ductility of reinforced concrete beam sections has been proposed by taking into account strain rate sensitive constitutive behavior of concrete and steel, confinement of core concrete and degradation of cover concrete during load reversal under earthquake loading. The estimate of flexural ductility of reinforced concrete rectangular sections has been made for a wide range of tension and compression steel ratios for confined and unconfined concrete at a strain rate varying from $3.3{\times}10^{-5}$ to 1.0/sec encountered during normal and earthquake loading. The parametric studies indicated that flexural ductility factor decreases at increasing strain rates. Percentage decrease is more for a richer mix concrete with the similar reinforcement. The confinement effect has marked influence on flexural ductility and increase in ductility is more than twice for confined concrete (0.6 percent volumetric ratio of transverse steel) compared to unconfined concrete. The provisions in various codes for achieving ductility in moment resisting frames have been discussed.

FRP versus traditional strengthening on a typical mid-rise Turkish RC building

  • Smyrou, Eleni
    • Earthquakes and Structures
    • /
    • v.9 no.5
    • /
    • pp.1069-1089
    • /
    • 2015
  • This paper investigates the limits and efficacies of the Fiber Reinforced Polymer (FRP) material for strengthening mid-rise RC buildings against seismic actions. Turkey, the region of the highest seismic risk in Europe, is chosen as the case-study country, the building stock of which consists in its vast majority of mid-rise RC residential and/or commercial buildings. Strengthening with traditional methods is usually applied in most projects, as ordinary construction materials and no specialized workmanship are required. However, in cases of tight time constraints, architectural limitations, durability issues or higher demand for ductile performance, FRP material is often opted for since the most recent Turkish Earthquake Code allows engineers to employ this advanced-technology product to overcome issues of inadequate ductility or shear capacity of existing RC buildings. The paper compares strengthening of a characteristically typical mid-rise Turkish RC building by two methods, i.e., traditional column jacketing and FRP strengthening, evaluating their effectiveness with respect to the requirements of the Turkish Earthquake Code. The effect of FRP confinement is explicitly taken into account in the numerical model, unlike the common procedure followed according to which the demand on un-strengthened members is established and then mere section analyses are employed to meet the additional demands.