Research On Composite Structure Of Concrete-Filled GFRP Tubes

The concrete-filled Glass Fiber Reinforced Polymer tubular structure evolved from the concrete-filled steel tube. Comparing with the concrete-filled steel tube, the GFRP tube has the hight-strength and counter-corrosion characters. The concrete-filled FRP tubes can improve the performance of the concrete. They may adapt to the especial demands of the environment to the structure. In the recently years, it becomes a hot spot among scholars at home and abroad in the composite research.According to the characters of the composite strucure of concrete-filled GFRP tube, research status quo and the actual problems, around the concrete-filled GFRP tubular column, some work has been done by the experimental and theoretical methods and the major contect are the following:1) Through the limit equilibrium anslysis and combining the ottosen criterion and Tsai-Wu criterion, the ultimate bearing capacity calculation of the reinforced concrete-filled GFRP tubular column is proposed. By data regression method, the parameters in the slenderness reduction factor formula and the formula reduction factor is determined. The calculated results are agreed with the experimental results, and they are good degree of agreement.2) Based on the experiments on the reinforced concrete-filled GFRP tubular column under low cyclic reversed loads, influences of axial load, concrete strength and the connection of GFRP tube with the foundation are analyzed. The experimental results showed that the reinforced concrete-filled GFRP columns have good seismic performance, but the ductility and stiffness rapidly decline with the increase of the axial compression.3) On the basis of low cyclic reversed loads, the restoring force model of the reinforced concrete-filled GFRP tubular column is established by the entire process of analysis and test data regression method. The different reasons between the calculation results and the experimental are analyzed in order to improve the restoring force model of the reinforced concrete-filled GFRP tubular column.4) The connections are tested under low cyclic reversed loads. The experimental parameters included axial load ratio, stirrup ratio and concrete strength. Based on the failure modes, damage process, the measured curves, The stiffness or the strength degradation, the ductility and the energy dissipation are studied. The experimental results showed that the bearing capacity and seismic performance of composite structure beam-column joints have greatly enhance and improve than the ordinary beam-column joints of reinforced concrete structures, but the seismic performance is very weak. In particular, the ductily of the specimen under the low compression doesn't meet the minimum requirements. So, the strengthen measures to the joints, the ring beam, are proposed. By the experimental on the ring beam joints, the results show that the ring beam can not only improve the seismic performance of composite structure, but also changed the way the destruction of the node.5) Based on the node experimental studies in the composite structure, further analysis of the stress mechanism, failure mode, has been done. The destruction of the ring beam process and the fundamental mechanism are also briefly analyzed, the ring beam of the internal force calculation has been proposed.