The Experimental Study On GFRP-Concrete-Steel-Concrete Double-Skin Tubular Hybrid Columns Under Axial Compression

In recent years, the infrastructure construction of our country enters the fastigium, especially the coastal engineering. Most of these structures select concrete structure and the service life is generally required more than100years, including pier components of sea-crossing bridge and columns of the offshore platform as the most important mechanical components. The corrosion resistance of the structure is so vital that the durability of the structure is put at a higher position.Prof. Teng, who works in the Hong Kong Polytechnic University, has recently proposed Hybrid FRP-concrete-steel double-skin tubular column (DSTC) which is a new form of hybrid columns. In this paper, the object of study is GFRP-concrete-steel-concrete double-skin tubular hybrid column (called hybrid column). The hybrid column is formed by pouring concrete into the multiple tube which is generated on the basis of DSTC. For the form of hybrid column, both the constraint of multiple tube and the durable performance of the GFRP tube can be taken full advantage of. The ten hybrid columns subjected to axial compressive loading were tested in this article. And the major effective factors, such as the thickness of interlayer concrete, the species of interlayer concrete (ordinary concrete, self-compacting concrete, self-stressing and self-compacting concrete) and the loading methods, were researched in this paper. Conclusions are drawn as follows:(1) Whatever the loading methods are. the hybrid columns are showing good ductility. While the interlayer thickness is larger, the ductility of specimen is better. By the comparison of three kinds of interlayer concrete, with the comprehensive consideration of the bearing capacity and the ductility, the self-compacting concrete is perferred to be used.(2) By analyzing the collaborative performance of the hybrid columns under core loading conditions, the smaller interlayer thickness can reflect the better collaborative performance. The self-stressing and self-compacting concrete is superior to other materials. There is no obvious difference with the comparison of the hybrid columns under full-sectional loading condition.(3) In terms of the constraint of multiple tubes, the greater interlayer thickness of the concrete makes the strength of multiple tube’s constraint stronger. Compared with the full-sectional loading column, the constraint of the hybrid columns from the core loading ones is more outstanding.(4) Based on the stress-strain model of FRP confined concrete, the computational formulas of the core loading hybrid columns about concrete compressive strength, bearing capacity and limit axial strain were proposed by the regression analysis of the experimental datas.