Research On Seismic Behavior Of Prestressed Concrete Frames Based On Beam-Column Joint Model

Prestressed concrete structures are suitable for large-span buildings and bridges,and its seismic performance is a matter of great concern to both academic and engineering communities.In this paper,the finite element model for calculating the nonlinear behavior of prestressed concrete frames is established by using the beam-column jont model and beam-column fiber elements in the finite element software OpenSEES The horizontal low-cycle repeated load test of the prestressed concrete frame that has been completed by domestic researchers is simulated by using this model and the applicability and reliability of the model are verified.Finally,the paper analyzes the main parameters affecting the ductility and energy dissipation capacity of the structure,and obtains some meaningful conclusions,which can provide reference for the research and design of prestressed concrete frames.The main work done in this paper is as follows:(1)After reading the relevant literatures at home and abroad,the general situation of the experimental research and the finite element analysis of the prestressed concrete frame are summarized.The failure mechanism of the beam-column joints,beam-column members and the energy-consuming mechanism of the frame structure are expounded.(2)The whole process of establishing the finite element model of prestressed concrete frame is expounded,including the selection of material constitutive model,the selection of beam and column fiber unit,the simulation of prestressed tendons,the selection of joint elements and the determination of shear stress strain curve.The horizontal low-cycle repeated load test of prestressed concrete frame completed by domestic scholar is simulated according to three finite element models like considering beam-column joint model,not considering joint and considering rigid domain.The simulation results show that the simulation results are the best when considering the beam-column joint model.The finite element model at this time can better simulate the strength degradation,stiffness degradation and pinching phenomenon of the structure during repeated loading.(3)The finite element model of prestressed concrete frame established by considering the beam-column joint model is used to numerically analyze the other nine-story prestressed concrete frame test completed by domestic scholars.Thecalculated load-displacement curve is basically consistent with the experimental results.The finite element model of the whole structure based on the beam-column node model has good applicability and reliability.(4)Design 30 specimens of prestressed concrete frame,and the variation parameters of the specimens were axial compression ratio,prestressing degree,column reinforcement ratio,beam reinforcement ratio and joint volume ratio.The load-displacement curves of the specimens under horizontal low-cycle reciprocating loading are numerically analyzed.The effects of these five parameters on the seismic behavior of prestressed concrete frames are analyzed from three aspects: anti-side bearing capacity,displacement ductility and energy dissipation capacity.The analysis results show that in order to make the structure have better seismic performance,the axial compression ratio should not exceed 0.7;the prestressing limit can be increased to 0.8;the column reinforcement ratio is controlled within 1.0%~2.5%;the beam reinforcement ratio is controlled at Within 1.0%~2.5%;the joint volume ratio is controlled within 1.0%~1.8%.