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Computers and Concrete Volume 29, Number 1, January 2022 , pages 15-29 DOI: https://doi.org/10.12989/cac.2022.29.1.015 |
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Modeling of heated concrete-filled steel tubes with steel fiber and tire rubber under axial compression |
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Hassan Sabetifar, Mahdi Nematzadeh and Aliakbar Gholampour
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| Abstract | ||
| Concrete-filled steel tubes (CFSTs) are increasingly used as composite sections in structures owing to their excellent load bearing capacity. Therefore, predicting the mechanical behavior of CFST sections under axial compression loading is vital for design purposes. This paper presents the first study on the nonlinear analysis of heated CFSTs with high-strength concrete core containing steel fiber and waste tire rubber under axial compression loading. CFSTs had steel fibers with 0, 1, and 1.5% volume fractions and 0, 5, and 10% rubber particles as sand alternative material. They were subjected to 20, 250, 500, and 750oC temperatures. Using flow rule and analytical analysis, a model is developed to predict the load bearing capacity of steel tube, and hoop strain-axial strain relationship, and axial stress-volumetric strain relationship of CFSTs. An elastic-plastic analysis method is applied to determine the axial and hoop stresses of the steel tube, considering elastic, yield, and strain hardening stages of steel in its stress-strain curve. The axial stress in the concrete core is determined as the difference between the total experimental axial stress and the axial stress of steel tube obtained from modeling. The results show that steel tube in CFSTs under 750oC exhibits a higher load bearing contribution compared to those under 20, 250, and 500oC. It is also found that the ratio of load bearing capacity of steel tube at peak point to the load bearing capacity of CFST at peak load is noticeable such that this ratio is in the ranges of 0.21-0.33 and 0.31-0.38 for the CFST specimens with a steel tube thickness of 2 and 3.5 mm, respectively. In addition, after the steel tube yielding, the load bearing capacity of the tube decreases due to the reduction of its axial stiffness and the increase of hoop strain rate, which is in the range of about 20 to 40%. | ||
| Key Words | ||
| axial compression; concrete-filled steel tube (CFST); elevated temperature; hoop strain; steel fiber; waste tire rubber | ||
| Address | ||
| Hassan Sabetifar: Department of Civil Engineering, Faculty of Engineering and Technology, University of Mazandaran, Babolsar, Iran Mahdi Nematzadeh: Department of Civil Engineering, Faculty of Engineering and Technology, University of Mazandaran, Babolsar, Iran Aliakbar Gholampour: College of Science and Engineering, Flinders University, SA, Australia | ||