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Steel and Composite Structures   Volume 22, Number 5, December10 2016, pages 937-974
Confinement models for high strength short square and rectangular concrete-filled steel tubular columns
Farhad Aslani, Brian Uy, Ziwen Wang and Vipul Patel

Abstract     [Buy Article]
    While extensive efforts have been made in the past to develop finite element models (FEMs) for concrete-filled steel tubular columns (CFSTCs), these models may not be suitable to be used in some cases, especially in view of the utilisation of high strength steel and high strength concrete. A method is presented herein to predict the complete stress-strain curve of concrete subjected to tri-axial compressive stresses caused by axial load coupled with lateral pressure due to the confinement action in square and rectangular CFSTCs with normal and high strength materials. To evaluate the lateral pressure exerted on the concrete in square and rectangular shaped columns, an accurately developed FEM which incorporates the effects of initial local imperfections and residual stresses using the commercial program ABAQUS is adopted. Subsequently, an extensive parametric study is conducted herein to propose an empirical equation for the maximum average lateral pressure, which depends on the material and geometric properties of the columns. The analysis parameters include the concrete compressive strength (fc = 20 - 110 N/mm2), steel yield strength (fy = 220 - 850 N/mm2), width-to-thickness (B/t) ratios in the range of 15-52, as well as the length-to-width (L/B) ratios in the range of 2-4. The predictions of the behaviour, ultimate axial strengths, and failure modes are compared with the available experimental results to verify the accuracy of the models developed. Furthermore, a design model is proposed for short square and rectangular CFSTCs. Additionally, comparisons with the prediction of axial load capacity by using the proposed design model, Australian Standard and Eurocode 4 code provisions for box composite columns are carried out.
Key Words
    composite columns; flexural stiffness; reliability analysis
(1) Farhad Aslani:
School of Civil, Environmental and Mining Engineering, The University of Western Australia, Crawley, WA 6009, Australia;
(2) Farhad Aslani, Brian Uy, Ziwen Wang:
Centre for Infrastructure Engineering and Safety, The University of New South Wales, Sydney NSW 2052, Australia;
(3) Brian Uy:
School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia;
(4) Vipul Patel:
School of Engineering and Mathematical Sciences, College of Science, Health and Engineering, La Trobe University, Bendigo, VIC 3552, Australia.

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