Experimental Study On Capacity Of FRP-Concrete-Steel Double-Skin Tubular Columns

Fiber reinforced polymer (FRP) has drawn more and more attention of the researchers in and abroad due to its advantages such as high strength-to-weight ratio and good corrosion resistance. FRP-concrete-steel double-skin tubular column (DSTC) is a new kind of hybrid column which makes full use of the features of FRP. In this type of new hybrid columns, the three constituent materials are optimally conbined to achieve several advantages not available with existing columns. This paper aims at the experimental study on the ultimate capacity of short DSTCs under axial compression and slender DSTCs under eccentric compression.Firstly, Tests of short DSTCs subjected axial load and slender DSTCs subjected to eccentric load are implemented to study the effect of load eccentricity, thickness of FRP tube and the size of the inner void on the performance of DSTCs. The production process of the columns is elaborated as well as the mechanical tests on the GFRP tube, seamless steel pipe and self-compacting concrete.Next, the experimental phenomena, failure modes and performance of FRP tube, concrete and steel pipe in DSTCs under axial and eccentric compression are discussed. The influence of the principal factors, such as load eccentricity, thickness of FRP tube and the size of the inner void, on the ultimate capacity and ductility of DSTCs is researched. Besides, the axial strain distribution of slender DSTCs under eccentric load is also studied.Then, based on the existing experimental conclusions and the reliable stress-strain model of DSTC confined concrete, a simple method to predict the ultimate capacity of short DSTCs under axial compression is proposed. Comparisons with test results show that the proposed formula provides accurate predicitions.Finally, existing method on the capacity of slender DSTCs subjected to eccentric load is used to predict the ultimate bearing capacity. The results are in reasonably close agreement with the test datum, and most of predictions are conservative.