Axial Compression Test Of BFRP-Recycled Concrete-Steel Double-Skin Tubular Columns

With the rapid development of all kinds of composite materials, numbers of new types of composite structure emerged constantly. Fiber reinforced polymer (FRP) has been researched and applied in civil engineering field in and abroad due to its advantages such as high strength-to-weight ratio and good corrosion resistance. The application of FRP composite materials in civil engineering structural startedlate at home, but develops rapidly and people already have a lot of scientific achievements.FRP tube-concrete-steel double-skin tubular column is a new form of combination column which makes full use of the features of FRP and recently proposed by Prof Teng J G in The Hong Kong Polytechnic University. The column consists of an outer tube made of fiber-reinforced polymer, an inner tube made of steel, and the concrete between them, the three constituent materials are optimally combined to achieve several advantages not available with existing columns. Because the test and theory research are not yet mature about this new type of combination column, this paper will make the following research:(1)The axial compression test of BFRP tube-concrete-steel double-skin tubular columnsTo study the mechanical behaviors and the failure modes about the BFRP tube-concrete-steel double-skin tubular columns under the axial compression, in view of the influencing factors such as the thickness of BFRP tube, the steel pipe radius-thickness ratio, the concrete section hollow ratio, the replacement rate of recycled aggregate, the strength of concrete, this paper designed 3 different kinds of steel pipe radius-thickness ratio and 5 different kinds of the replacement rate of recycled aggregate. A total of 15 BFRP tube-recycled concrete-steel double-skin tubular columns were tested under monotonic axial compression. In the experiment, failure process and phenomenon were recorded.In this paper, by testing the ultimate strength of BFRP tub-recycled concrete steel double skin tubular column, the axial strain and the hoop strain of BFRP sheets and steel tube. According to the load-displacement and the load-strain curves, this paper analyzed with the different steel pipe radius-thickness ratio and different replacement rate of recycled aggregate influence factors, various performance indicators of BFRP tub-recycled concrete-steel double-skin tubular columns under axial compression.(2)Checking the DSTC core concrete stress-strain model and the existed formula of the bearing capacityBased on the existed experiment phenomenon and the conclusion,according to the existed form of concise FRP tube confine concrete stress-strain models, On this basis, compared with another more simple and high precision of confined concrete model of stress and strain of confined concrete by considering the influence of hollow ratio, and verified by the test data that is collected for the kinds of bearing capacity calculation formula of calculation accuracy, results show thatunder the formula calculation results are in good agreement with which use the stress-strain model of Yutao.