Abstract
Hybrid FRP-concrete-steel double-skin tubular columns (hybrid DSTCs) are novel hollow columns consisting of an outer FRP tube, an inner steel tube, and the concrete between the two tubes. Hybrid DSTCs possess important advantages, such as excellent corrosion resistance as well as remarkable seismic resistance. However, existing studies are mainly focused on hybrid DSTCs with a circular cross section or a square cross section. When a column is subjected to different load levels in the two horizontal directions, a rectangular column is preferred as it can provide different bending stiffness and moment capacity around its two axes of symmetry. This paper presents an experimental study on rectangular DSTCs with a particular focus on the effect of the cross-sectional aspect ratio (i.e., the ratio of the breadth to the width of the rectangular cross section). The effect of the cross-sectional shape of the inner steel tube (i.e., both elliptical and rectangular inner steel tubes were used) and the effect of FRP tube thickness were also investigated experimentally. Experimental results show that a larger aspect ratio will have no negative effect on the confinement effect in rectangular DSTCs; a rectangular DSTC with a larger aspect ratio generally has a larger ultimate axial strain and a higher axial stress at the ultimate axial strain; rectangular DSTCs with an elliptical steel tube generally have better performance than corresponding specimens with a rectangular steel tube. An existing model, which was developed based on a model for rectangular FRP-confined concrete columns and a model for circular DSTCs, is verified using the test results of the present study. The model generally provides close predictions for the peak axial stress of the confined concrete but yields conservative predictions for the ultimate axial strain for rectangular DSTCs.
Highlights
In the field of civil engineering, FRP composites have found increasing applications for the retrofitting of existing structures as well as the construction of new structures [1,2,3]
Hybrid DSTCs are quite suitable for structural members in harsh environments due to their excellent corrosion resistance, which is enabled by the use of the outer FRP tube
E present study extends the existing work to rectangular DSTCs subjected to axial compression with a particular focus on the effect of the aspect ratio, which is the ratio of the breadth to the width of the rectangular cross section. e effect of the crosssectional shape of the inner steel tube and the effect of the FRP tube thickness are investigated experimentally
Summary
In the field of civil engineering, FRP composites have found increasing applications for the retrofitting of existing structures as well as the construction of new structures [1,2,3]. FRP composites are attractive for use in combination with traditional construction materials (i.e., concrete, steel, and timber) to create novel hybrid structures [4]. Rectangular FRP-confined concrete columns have received extensive research attention in the last decade [24,25,26,27,28,29,30], but experimental research on rectangular DSTCs is rather rare. Cavill and Yu [31] confirmed the concrete in rectangular DSTCs was effectively confined by the FRP tube and the steel tube, leading to a very ductile response. E present study extends the existing work to rectangular DSTCs subjected to axial compression with a particular focus on the effect of the aspect ratio, which is the ratio of the breadth (the longer side) to the width (the shorter side) of the rectangular cross section. Rectangular FRP-confined solid concrete columns are fabricated and tested for comparison with rectangular DSTCs
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