Seismic Behavior of Reinforced Concrete T-shaped Columns Under Compression-flexure-shear and Torsion Combined Action

In order to investigate the seismic behavior of reinforced concrete T-shaped column under compression-flexure-shear and torsion, a total of six reinforced concrete(RC) T-shaped columns with varying parameters of axial compression ratio, torsion-bending ratio and height-thickness ratio of flange plate were designed and tested under constant axial compression force and quasi-static reversed cyclic loading.The failure process and modes of the specimens were observed, and the hysteretic loops of torsion moment-torsion rotation angle and load-displacement were obtained respectively.Based on the experimental data, the influence of different parameters on seismic performance index of RC T-shaped columns were analyzed.The test result shows that with the increase of torsion-bending ratio, the failure modes of RC T-shaped columns were bending, bending-torsion and torsion-shear failure.Compared with n=0.3,the torsional ductility and flexural ductility of specimens with n=0.36 were increased by 31% and 63% respectively.When the torsion-bending ratio was 0.08~0.21,with the increase of torsion-bending ratio, the ultimate torsional capacity and the ultimate torsion angle of specimens were increased by 34%~52% and 35%~58% respectively.And the ductility coefficient of the angle were increased by 24%~38%.In the range of ξ=2.5~3.0,the smaller the height-thickness ratio of flange plate, the lower the bending capacity and torsional capacity index of RC T-shaped columns, but the higher the torsional and horizontal displacement ductility coefficients.The energy dissipation capacity of specimens mainly depend on the bending and shear energy dissipation capacity.Increasing the axial compression ratio and torsion-bending ratio will make the torsional and lateral stiffness degradation of RC T-shaped columns faster.The degradation coefficients of torsional strength are between 0.80 and 0.98,and that of bending strength are between 0.75 and 1.00.