Two-dimensional Seismic Behaviors And Designs On Spatial Frame Joints Of Reinforced Concrete And Prestressed Concrete Structures

The seismic responses of structures are multiple dimensions undermulti–component ground motion inputs, the research on the elasto-plastic seismicbehaviors of structures and members under multi–dimensional earthguake excitationhas attracted extensive interests in recent times. This paper describes the seismicperformance and design method of reinforced concrete and prestressed concretespatial frame joints under two-dimension low cyclic lateral loading. The mainachievements can be summarized as follows:(1)The experimental results of twelve reinforced concrete and prestressed concreteframe joints under biaxial cyclically increasing horizontal displacement loading werepresented in this paper, the mainly parameters are the types of joints, ratio of axialcompression, PPR，line stiffness ratio of framework beam and column, loading wayetc. The aseismatic capacities of failure mode, hysteretic characteristics, mechanicalmechanism of joint cores, the bone slip between reinforcement and concrete,ductility,dissipated energy, the strength degeneration and stiffness degradation wereinvestingated.(2)Analytical models of reinforce concrete and prestressed concrete frame jointsunder biaxial cyclically increasing horizontal displacement loading weredeveloped by finite element analysis (FEA) software ABAQUS. The hystereticcurves and skeleton curves were analyzed. The calculated results were verified byexperimental results. The hysteretic characteristics, the stress and strain of jointcore were clarified, the parameter analysis were carried out. Based onpseudo-static test and finite element analysis, the effect such as types ofjoints,ratio of axial compression, PPR, line stiffness ratio of framework beam andcolumn and loading way on aseismatic capacities of frame joints wereresearched.(3)Based on the experiment and theory analysis, the restoring force model underbiaxial cyclic lateral loading had been established. The governing criteria and design method of seismic behavior of joints under two-dimension seismic excitationwere analyzed compared with current seismic code, the results show that thesecond-order effect of torsion under multi–dimensional earthguake can’t beneglected, the suggested calculating formula for spatial frame joints are made, and thedesign rules under two-dimensional earthguake were suggested in this paper.