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Steel and Composite Structures   Volume 24, Number 3, June30 2017, pages 323-337
Compressive behaviour of circular steel tube-confined concrete stub columns with active and passive confinement
Mahdi Nematzadeh, Iman Hajirasouliha, Akbar Haghinejad and Morteza Naghipour

Abstract     [Full Text]
    This paper presents the results of a comprehensive experimental investigation on the compressive behaviour of steel tube-confined concrete (STCC) stub columns with active and passive confinement. To create active confinement in STCC columns, an innovative technique is used in which steel tube is laterally pre-tensioned while the concrete core is simultaneously pre-compressed by applying pressure on fresh concrete. A total of 135 STCC specimens with active and passive confinement are tested under axial compression load and their compressive strength, ultimate strain capacity, axial and lateral stress.strain curves and failure mode are evaluated. The test variables include concrete compressive strength, outer diameter to wall thickness ratio of steel tube and prestressing level. It is shown that applying active confinement on STCC specimens can considerably improve their mechanical properties. However, applying higher prestressing levels and keeping the applied pressure for a long time do not considerably affect the mechanical properties of actively confined specimens. Based on the results of this study, new empirical equations are proposed to estimate the axial strength and ultimate strain capacity of STCC stub columns with active and passive confinement.
Key Words
    compressive behaviour; pre-compressed concrete; active confinement; steel tube-confined concrete; stub column
(1) Mahdi Nematzadeh, Akbar Haghinejad:
Department of Civil Engineering, University of Mazandaran, Babolsar, Iran;
(2) Iman Hajirasouliha:
Department of Civil and Structural Engineering, University of Sheffield, Sheffield, UK;
(3) Morteza Naghipour:
Faculty of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran.

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