Seismic behavior of steel-tube reinforced-concrete(STRC) and steel reinforced-concrete(SRC) columns

In this paper,6 columns were tested to study the seismic behavior of 3 types of columns including reinforced-concrete(RC) columns,steel reinforced-concrete(SRC) columns and steel-tube reinforced-concrete(STRC) columns.The columns were tested under combined constant axial compression and cyclic lateral loads.Each type of columns consisted of 2 specimens with shear span to depth ratio to be 1.5 and 3.0 respectively.The geometry parameters and axial force of these columns were identical,and steel amount of SRC and STRC columns was the same.The test results indicate that the deformation ability of RC and SRC columns with the shear span to depth ratio 1.5 does not meet the requirement of Chinese code for seismic design.The bending strength and shearing strength of SRC columns are higher than those of STRC columns,but the ductility,deformation ability and energy dissipation ability are opposite.The shearing strength of STRC short column is not obviously improved by the outer steel tube,but the deformation ability and ductility are greatly improved due to the confinement of the steel tube to the core concrete.Based on the experimental results,a design method is proposed to calculate the shear strength of STRC columns.