| In this thesis, a total of 7 nearly full-scale exterior beam-column joints of RC frame, with different shear-compression ratios and stirrup ratios, were tested under reversed cyclic loading. The damage developing process of the joint core zone was carefully monitored and investigated, and three shear failure modes of the joints could be summarized: inclined-tension failure mode, inclined-compression failure mode and shear-compression failure mode. The exterior joints had some failure characteristics differing from the interior joints, such as: (a) the direction of the cracks in the exterior joint core zone were apt to be vertical; (b) the shear cracks of exterior joint extend into the inside of the column; (c) the concrete of the exterior joint, where no confinement could be provided by the lateral beam, would have more serious damage.The shear capacity, the ductility, the energy-dissipation capacity, the deterioration of the shear capacity and the deterioration of the stiffness were all analyzed by comparing the 7 exterior joints which were conducted by the author, and another 5 corner joints which were tested by Mr. Ma Haibin, a member of the author's research group. The comparison showed that: the member which has a bending failure mode at the beam end or a shear compression failure mode in the joint core zone will exhibit better seismic behavior. So these two failure modes should be induced when the exterior joints are designed.By reference of recent experiment researches on the interior joints, 3 shear transfer mechanisms could be confirmed existing in the exterior joints: the truss mechanism, the strut mechanism and the confinement mechanism. 3 models for the shear capacity of the exterior joints were proposed: the shear-friction model, the strut model and the combination model, which were suitable for different failure modes.According to the characteristics of the exterior joints, the shear-compression ratio and the stirrup ratio were considered to be the most affecting factors to the seismic behaviors of the exterior joints. However, by re-identifying the"shear capacity", the two-term shear capacity equation in Chinese Code GB50010-2002 is not reasonable. The ductility of the joint, rather than the shear capacity, was more important to estimate its seismic behavior. Based on the experiment results, a design criteria, which was suitable for shear capacity of the exterior joints, was proposed. |
