Study On Seismic Performance Of Beam-to-column Of FRP-steel-concrete Composite Structures

Fiber reinforeced polymer tube-concrete-encased steel(FTCES),as a new type of structural element,can not only bring into play the performance advantages of FRP,steel and concrete,but also combine the three organically to further enhance the mechanical properties of the combined elements.In recent years,most of the research on FTCES has been focused on structural members such as beams and columns,but not enough research has been done on their connection with other structural members,which seriously restricts the application of new structural members in practical engineering.To this end,this paper proposes an RC ring beam joint for connecting FTCES columns with Reinforced concrete(RC)/steel reinforced concrete(SRC)beams.Based on low circumferential reciprocal loading tests,the effects of different design parameters on the seismic performance of the joint are investigated,and the joint is parametrically analyzed with the Open Sees finite element analysis platform.The main works are as follows:1.low circumferential reciprocal loading tests were conducted on four specimens of a new FRP-steel-concrete composite structural beam-column joint with different axial compression ratios,ring beam reinforcement ratios and beam types.The test results show that the new combined beam-column joints have reliable connection performance and good seismic performance,and the damage modes of each specimen can be classified into three kinds,i.e.,plastic hinge occurs at the end of frame beam,at the connection between frame beam and ring beam and on the ring beam,respectively."2.The FRP tubes were established by Open Sees.2.The finite element analysis model of the beam-column joints of the FRP-steel-concrete composite structure was established by Open Sees,and the accuracy of the finite element model was verified by comparing the performance parameters such as hysteresis curve,skeleton curve,yield point and peak point with those of the test specimens.3.The finite element analysis model of FRP-steel-concrete composite beam-column joints based on Open Sees was developed with eight design parameters as variables,including column axial compression ratio,cross-sectional dimensions and thickness of FRP tubes,ring beam diameter and reinforcement ratio,concrete strength,steel strength and beam longitudinal reinforcement ratio in the frame beam.In addition,when the reinforcement ratio of the ring beam is too low(less than 2.5%),the restraint effect of the ring beam on the joint is smaller,and the joint bearing capacity and ductility will be significantly reduced at this time.Therefore,it is recommended that the reinforcement ratio of the ring beam should not be less than 2.5%during design.