Seismic Performance Of FRP-Steel Composite Tube Confined Columns

A new type of Fiber Reinforced Polymer (FRP)-steel composite tube confined RC(SRC) columns was proposed in the paper by combining corrosion-resistant FRP material with steel tube confined RC (SRC) columns to solve the problems of local buckling and poor durability in concrete-filled steel tube column. Experimental study and theoretical analysis of the proposed new columns were conducted. The main works of this paper is follows as:(1) The behavior of FRP-STEEL composite tube confined RC columns was studied by testing three GFRP-STEEL composite tube confined RC columns, one CFRP-STEEL composite tube confined RC columns, one steel composite tube confined RC column and one RC column. The test parameters was the layer number of GFRP(6 layers or 8 layers),fiber types(GFRP or CFRP) and ratio of axial load(0.3 or 0.45). The test results indicated that steel tube and core concrete were restrained by GFRP(CFRP), and the bearing capacity, ductility and energy dissipation of FRP-STEEL composite tube confined RC columns were improved by the effective restraining of GFRP(CFRP). With the increase in ratio of axial load, the improving on the bearing capacity was more obvious and the ductility was worse.(2) The behavior of FRP-STEEL composite tube confined SRC columns was studied by testing two FRP-STEEL composite tube confined SRC columns and one steel composite tube confined SRC column. The test parameters was the layer number of GFRP(6 layers or 8 layers). The test results indicated that steel tube and core concrete were restrained by GFRP, and the bearing capacity, ductility and energy dissipation of FRP-STEEL composite tube confined SRC columns were improved by the effective restraining of GFRP. With the increase in the layer number of GFRP, the improving on the bearing capacity, ductility and energy dissipation of FRP-STEEL composite tube confined SRC columns was more obvious. The initial stiffness of test specimens was hardly affected by GFRP. With the increase in the layer number of GFRP, the degradation of late stiffness was more slow.(3) This paper simulated the behavior of FRP-STEEL composite tube confined RC(SRC) columns, simulated results are in good agreement with the experimental results, which verified the correctness of the model. The further parametric analysis shows the bearing capacity, ductility and energy dissipation were improved by the improvement in thickness of steel tube or reinforcement ratio. With the increase in ratio of axial load, the improving on the bearing capacity was more obvious and the ductility was worse.