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Steel and Composite Structures
  Volume 38, Number 6, March25 2021 , pages 739-749
DOI: https://doi.org/10.12989/scs.2021.38.6.739
 


An approach for partial strengthening of circular RC columns using outer steel tube
Ju-young Hwang and Hyo-Gyoung Kwak

 
Abstract
    This paper introduces an improved design equation to evaluate the resisting capacity of circular reinforced concrete (RC) columns partially strengthened with outer steel tube. When RC column members are required to be strengthened according to the change in the loadings considered and/or the deterioration progress in columns, wrapping up RC column with steel circular tube, which takes the form of concrete filled steel tube (CFST), has been popularly considered because of its structural advantage induced from the confinement effect. However, the relatively high construction cost of steel tube is restricting its use to the required region, while deriving the shape of a partial CFST column. To evaluate the resisting capacity of a partial CFST column, numerical analyses need to be performed, and a numerical model proposed in the previous study for the numerical analysis of full CFST columns is used to conduct parametric studies for the introduction of a design equation. The bond-slip effect developed along the interface between the in-filled concrete and the exterior steel tube is taken into consideration and the validity of the numerical model has been established through correlation studies between experimental data and numerical results for partial CFST circular columns. Moreover, parametric studies make it possible to introduce a design equation for determining the optimum length of outer steel tube which produces partial CFST circular columns.
 
Key Words
    concrete filled steel tube; Partial strengthening; P-M interaction diagram; design equation; circular RC column
 
Address
Ju-young Hwang: Department of Civil Engineering, Dong-Eui University, 176 Eomgwangno, Busanjin-gu, Busan, Republic of Korea
Hyo-Gyoung Kwak: Department of Civil and Environmental Engineering, Korea Advanced Institute for Science and Technology,
291 Daehak-ro, Yuseong-gu, Daejeon, Republic of Korea
 

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