Numerical Study on Discrete Confinement of Circular RC Column Subjected to Eccentric Load

Sandy I. Yansiku1, Bambang Piscesa1, *, Priyo Suprobo1
1 Civil Engineering Department, Institut Teknologi Sepuluh Nopember, Surabaya 60111, East Java, Indonesia

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© 2023 Yansikun et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at Civil Engineering Department, Institut Teknologi Sepuluh Nopember, Surabaya 60111, East Java, Indonesia; Email:



The performance of concrete-filled steel-tube (CFST) columns under axial compression is excellent. However, the steel-tube wall's instability due to insufficient outward restraint from the concrete made the steel tube lose its lateral support, thereby making it more susceptible to buckling.


This study aims to propose and investigate a confinement mechanism that can remove the possibility of buckling of the steel tube by introducing gaps and pre-tension to prevent tube detachment from concrete. The investigation was carried out using both experimental tests and numerical simulation.


The proposed confinement mechanism consists of thin steel sheets with gaps between them and is pre-tensioned in a staggered scheme. The performance of the proposed confinement mechanism is evaluated through experimental tests and numerical simulations using an in-house 3D-NLFEA package. The observed behaviors are the axial stress-strain, strength index, initial confining pressure, and ductility.


Experimental works found that the primary failure mode in the compression zone of the strengthened column was due to lateral expansion of concrete which may be attributed to strain localization, longitudinal tensile cracking, and severe concrete crushing. On the other hand, at the tensile region, pure tensile forces occurred, followed by crack opening displacement at the outer tensile fiber region. With the proposed confinement mechanism, the extreme failure event can be reduced. The axial capacity and ductility of the strengthened column were enhanced. The numerical model presented the initial confining pressure by the pre-tensioned steel sheet (a clamping mechanism), which successfully increased the axial load capacity of the slender reinforced concrete (RC) column and reduced the possibility of cover spalling.


The proposed confinement mechanism to strengthen an RC column was found to successfully enhance the load-carrying capacity and ductility of a slender circular reinforced concrete column.

Keywords: Confinement, Thin steel sheets, External prestressed confinement mechanism, Finite element, Concrete-filled steel tubes.