SPATIAL MECHANICAL PERFORMANCE OF STEEL REINFORCED CONCRETE FRAMES WITH SPECIAL-SHAPED COLUMNS

To study the spatial mechanical performance of steel reinforced concrete frames with special-shaped columns, a five-story two-direction two-span spatial frame model was tested under low cyclic reversed loading. The failure modes, hysteretic curves and skeleton curves were obtained. The seismic performance indexes such as the ductility, story drift ratio, stiffness, and energy dissipation were analyzed. Based on the experimental study, a finite element model of the spatial frame was established by using OpenSees. The analysis results agreed well with the experimental results. The failure mechanism and the cooperative work mechanism were investigated. The influence of the axial compression ratio and column limb length-width ratio under different loading angles were analyzed. The results show that the beam ends failed earlier than the column ends, and the joints were less damaged. The damage of the edge frame was more serious than that of the middle frame. The plastic hinges of the spatial frame developed from the beam ends to the column ends, from the bottom to the top, and from the middle frame to the edge frame. The hysteretic curves were symmetric and full. The ductility was good. The energy dissipation capacity and the collapse resistance were large. The mechanical performance of the spatial frame was better than that of independent frames without connection. With the increment of loading angle, the strength and energy dissipation capacity were obviously increased, the initial stiffness was slightly increased, and the ductility was first increased and then decreased. With the same loading angel and increment of the axial compression ratio, the strength, ductility and energy dissipation capacity of the spatial frame were decreased, and the initial stiffness was first increased and then decreased. With the same loading angel and increment of the column limb length-width ratio, the strength, initial stiffness and energy dissipation capacity of the spatial frame were increased.