| This paper includes three parts of research:(1)Cyclic loading tests of sixteen interior joints with rectangualr columns and four joint subassemblages with circular columns. Based on measurement of strains of both horizontal stirrups in the joint core and longitudinal reinforcement passing througth the joint, in different stages,transfer mechanism and factors affacting seismic behavior of the joint, were analysed. Under different shear compression ration, effect of axial force ratio on seismic behawior of the joint was also evaluated, static shear and seismic shear of the joint based on capacity design were investigated. On this basis,new governing criteria and conditions of seismic behavior of the joint were put forward.(2)Based on deterioration model of owerage bond stress of beam reinforcement accounting for effect of axial compression ration and number of displacement loops,and stress-strain relationship of the concrete in the joint core accounting for effects of both softening and confinement, the modified compression field theory was employed to simulate behavior of the joint core under loading reversals. Analysis by means of the program JAP on the tested specimens in this paper and those obtained from other researchers produced consistent results. Predictions were made on the ductility of the joint core when shear compression ratio,reinforcement contant and axial force ratio were different.(3)Experimental results of interior joints on the top story, exterior joints in the intermediate stories,and knee joints are collected and summerized. Force transfer mechanisms of the three categories of joints were identified and analysed. Besides,compariative analysis was carried out on ductility and energy comsumption of the interior joints on the top story with 90?bent hooks,exterior joints in the intermediate stories with different detailing of longintudinal reinforcement in the columns,and the knee joints with different lap splices in the beam and the column under negative moments. Seismic anchorage and lap splices schemes were presented for the longitudinal rebars in the joint core.The creative results are as follows:(1)Behavior of the stirrup legs in the loading direction in the joint core (along the loading direction for circular stirrups)is different from that perpendicular to the loading direction. The stirrup legs in the loading direction acts as the tension chords in the truss model to resist shear,in the meantime,they confine the compressed diagonal strut from lateral expam-sion. For the stirrup legs perpendicular to the loading direction, they usually confine the strut from lateral expansion. The findings above confirm that there exsists three transfer mecha-nisms in the joint,that is,the truss mechanism,the diagonal strut mechanism,and the confinement mechanism. The first two mechanisms transfer joint shear,while the third inecha-nism provide ductility and energy dissipation capacity by confining the joint core concrete from lateral expansion.(2)From the equilibrium conditions of the isolated segment from a beam-column sub-assemblage, it is clarified for the first time that the bond stress along the beam rebars passing through the joint transfers into the column end to balance shear at this column end at the same ratio as that of the compression force in the compressed concrete at beam ends. In the way, a convincing expression is prsented to force transfer mechanism in the joint core. The findings shew that in different stages,the horizontal forces transfered into the joint are by the truss and the diagonal strut mechanisms are different. Behavior of the confinement mechamsm is also different. Before obvious bond deterioration of the beam rebars passing through the joint core occurs,the shear is mainly transfered by the truss mechansim. When the bond deterioration occurs comprehensively, the shear transfered by the truss mechamism is reduced significantly,the majority of the shear is transfered by the diagonal strut. At the time when reversed diagonal cracks develop fully, later...
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