Study On Seismic Performance Of Concrete Filled GFRP-Steel Tubes

Concrete filled GFRP-steel tube is a composed system made by wrapping around the steel tube with glass fibber reinforced polymer (GFRP) sheet and then filling concrete into the tube. Comparing with Concrete filled CFRP-steel tube structure, GFRP one has superior Seismic ductility and capacity of anti-impact except its economic advantages.For the propose of investigating the strengthening effectiveness of GFRP on concrete filled steel tube structure under combined seismic loading and comparing with CFRP ones,7 specimens of the same size strengthened by FRP (CFRP/GFRP) sheets with 1 or 2 layers orientated in different directions are studied experimentally by quasi-static test system. Combined loads including axial pressure and bending are applied to simulate the complex seismic loadings. The test results show that the technique of GFRP strengthening concrete filled steel tube is potential and effective for the improvements in energy dissipation of the structure, in spite of varying responses related on the bonding styles of FRP and the loadings modes. Test also shows that GFRP can work with steel tube better since its ultimate elongation is higher compared with CFRPFor the shortcomings of specimen number and experimental equipments, numerical simulations of quasi-static test are done on concrete filled FRP (GFRP/CFRP) with ABAQUS; the establishment of the mechanical properties of the finite element model on concrete filled FRP (GFRP/CFRP) components is proved to be feasible by comparing the load-displacement curve of finite element analysis with the experimental curves, further studies are carried by changing FRP (GFRP/CFRP)thickness and axial compression ratio, the results show that components with thicker FRP equip better dissipation capacity and higher bearing capacity; stiffness degradation become more serious as axial compression increase. In order to providing theoretical support for later further research, hysteretic mathematical models of concrete filled longitudinal FRP (GFRP/CFRP) steel tube are established on the basic of experimental and ABAQUS simulation. Comparing the mathematical models results with experimental and simulation results, the correctness of the hysteretic mathematical models are verified.