Experimental Study On Seismic Behavior Of FRP Reinforced Concrete Frame Joints Based On Plastic Rotation Mechanism

Compared with reinforced concrete structure,FRP(Fiber Reinforced Plastics)reinforced concrete structure has the disadvantages of poor ductility and low energy consumption,which restricts the wide application of FRP reinforcement in structures with seismic requirements.Therefore,further research on the failure mechanism and earthquake resistant behaviour of FRP reinforced concrete frame structure based on the ductility mechanism is carried out,and measures to enhance the ductility performance of FRP reinforced concrete frame structure are proposed,which is of great scientific significance for the engineering application of FRP reinforced concrete structure.In this paper,a kind of FRP plastic hinge joint is developed.Through reasonable design of the plastic hinge area of the beam and column embedded in the concrete structure,not only the ductility of the structure can be improved,the earthquake resistant behaviour of the structure can be enhanced,but also the durability of the structure can be improved.For this reason,the "T" and "Ten" joints of FRP reinforced concrete frame with plastic hinge joint are designed and manufactured,and the pseudo static test of low cycle repeated load is carried out to study the earthquake resistant behaviour of this new type of structure.Through the finite element model and analysis,the performance-based seismic design approach of FRP reinforced concrete frame structure is discussed.The specific research contents are as follows:1)A kind of plastic hinge joint of FRP bars for concrete structure is put forward,and the design and preparation approach are described.The uniaxial tensile tests of plastic hinge joints of BFRP bars,GFRP bars and FRP bars are carried out.The mechanical properties of plastic hinge joints of BFRP bars,GFRP Bars and FRP bars are studied.The failure mode,failure characteristics and the characteristics of stress-strain curve are analyzed and summarized.2)The specimens of reinforced concrete,FRP reinforced concrete and FRP reinforced concrete frame joints with plastic hinge connector are designed and manufactured.The pseudo static test of the specimens under the action of low cycle repeated load is carried out to study the stress,deformation and failure process of the joints under the same loading system and axial compression ratio.Then the ductility coefficient,energy dissipation,strengthdegradation and rigidity are given The earthquake resistant behaviour indexes,such as degree of deterioration,are used to comprehensively evaluate the comprehensive earthquake resistant behaviour of the structure,such as bearing capacity,deformation capacity,energy consumption capacity,strength and stiffness degradation.The experimental results show that the hysteretic curves of the joints are full,and the hysteretic properties of the joints are similar to those of the reinforced concrete structures,such as deformation capacity,energy dissipation capacity,strength and stiffness degradation,which are obviously superior to those of the joints.3)Based on the optimization of the plastic hinge constitutive relationship of reinforced concrete,the plastic hinge constitutive model of FRP reinforced concrete is proposed.The Pushover analysis approach in SAP2000 is used to analyze the FRP reinforced concrete frame structure with plastic hinge.The earthquake resistant behaviour of the frame structure is analyzed by the Pushover curve,and the seismic design approach of the FRP reinforced concrete frame structure is discussed.