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To study the seismic behavior of RCRC ultra short columns, the tests subjected to combined constant axial compression and cyclic lateral shear force of rectangular tubed RC (RTRC) columns including 4 RCRC and 2 common RC columns for comparison were carried out. The main parameters were axial load ratio (0. 3 and 0.5) and width to thickness ratio (111 and 166), and the shear span to depth ratio of all the tested columns was 1. O. The results indicated that the failure mode of common RC short columns was shear failure, therefore the RC columns showed little ductility and energy dissipating capacity. Under lateral shear force, RCRC short columns showed no shear failure due to the effective confinement from the outer tube to the core concrete. The RTRC columns showed higher ductility, elastic-plastic deformation capacity and energy dissipating capacity than the common RC columns. The lateral load strength of RCRC short columns increased with the increment in axial load ratio, while the ductility decreased a little, and the width to thickness ratio affected little on the seismic behavior of RTRC ultra short columns. [ABSTRACT FROM AUTHOR]

Two groups of specimens including 8 stub columns were tested to study the effect of bond stress between steel tube and core concrete on the axial loaded behavior of tubed high-strength stub columns ( HSC ). Each group included two columns without bond stress and two columns with bond stress. Elastic-plastic analysis on the steel tube during the loading procedure was carried out. The results from test and analysis indicate that the longitudinal stress of the steel tube is evidently decreased in respect that the bond effect is eliminated, while the bond stress has little effect on the axial load strength and ductility of tubed HSC. Therefore it is not necessary to eliminate the bond effect between the steel tube and the core concrete in structural engineering. [ABSTRACT FROM AUTHOR]

To investigate the seismic behavior and design method of tubed reinforced concrete (RC) beam--columns, circular tubed RC (CTRC) and square tubed RC (STRC) columns were experimentally studied. Results indicate that CTRC and STRC columns with high axial load ratio exhibit much higher flexural strength, displacement ductility and greater energy dissipation capability than common RC columns due to the effective confinement of the tube to the core concrete. The moment strength and ductility of CTRC columns are higher than those of STRC columns with the same axial load ratio and diameter--to--thickness ratio. The design method for steel tube confined RC beam--columns is proposed based on the experimental results. Fiber models are developed for CTRC and STRC beam--columns, and the analysis results of fiber models agree well with the experimental results. [ABSTRACT FROM AUTHOR]