Abstract
This research is aimed at investigating the structural improvements of concrete filled steel tubular (CFST) sections with normal strength concrete externally bonded with fibre reinforced polymer (FRP) composites. For this study, compact mild steel tubes were used with the main variable being FRP characteristics. Carbon fibre reinforced polymer (CFRP) fabrics was used as horizontal strips (lateral ties) with several other parameters such as the number of layers and spacing of strips. Among twenty one columns, eighteen were externally bonded by CFRP strips having a constant width of 50 mm with a spacing of 20 mm and 40 mm and the remaining three columns were unbounded. Experiments were undertaken until column failure to fully understand the influence of FRP characteristics on the compressive behaviour of square CFST sections including their failure modes, axial stress-strain behaviour, and enhancement in load carrying capapcity. It was found that the external bonding of CFRP strips provides external confinement pressure effectively and intended to delay the local buckling of steel tube and also to improve the load carrying capacity further.
Highlights
Composite construction may be considered as a reliable choice of attaining proper balance between the advantages it offers and the cost
From that it was observed that the control and confined columns exhibited the elastic behavior at initial stage followed by in-elastic response when increasing the load further and in addition significant fall in curve was observed at the peak stage due to sudden rupture of Carbon fibre reinforced polymer (CFRP)
Horizontal wrapping style of narrow strip of CFRP fabrics is proposed in this study for improving the confinement pressure of concrete filled steel tubular members externally
Summary
Composite construction may be considered as a reliable choice of attaining proper balance between the advantages it offers and the cost. An extensive variety of composite columns are available nowadays, but the concrete filled steel tubular (CFST) sections are most commonly used. Various strengthening or rehabilitation techniques such as section enlargement, external bonding of steel plates and fibers, etc. Section enlargement method has been proved as a suitable method for the rehabilitation of reinforced concrete columns. It was expected that this method will be effective in repairing of CFST columns. It resulted in a significant increase in the column cross-section and the construction time is too long. Compared to the above methods, plate bonding technique provides a practical and cost effective solution. Rehabilitation using fibre reinforced polymer (FRP) composites do not exhibit any of these drawbacks
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