The Research On The Performance Of T-shaped Concrete Columns Confined By Stirrups Under Axial Repeated Loading

The T-shaped column is a kind of the special-shaped column,the thickness of Tshaped column limb is the same as the wall,the edges of T-shaped colmn is hidden into the wall,the space of houses can be effectively increased,thus the application prospect of Tshped colunm is excellent.But the corss-section of T-shaped column is irregular,which makes the mechanical properties of T-shaped column different from the traditonal colunm like rectangular column.Reinforced concrete T-shaped column has poor deformation capacity and brittle failures can happen more easily,ductility and seismic performance cannot be easily guaranteed,configuring moderate amount of stirrups can restrain core concrete and improve its mechanical properties.In this paper 5 T-shaped columns confined by stirrups were tested under axial repeated compression loading while one was tested under axial loading,the failure process and failure characteristics affected by reinforcement characteristic value were studied,the test results show that specimens with low reinforcement characteristic value are easy to emerge oblique failure,the angle between failure surface and horizontal plane is 65°~75°,specimens with high reinforcement characteristic value are easy to emerge longitudinal failure.The stiffness degeneration and ductility affected by reinforcement characteristic value were studied,The test results show that as the reinforcement characteristic value increased,the stiffness degeneration of specimens is delayed effectively and the ductility of specimens becomes better.The calculation formula of ductility coefficient was established,the calculated results of ductility coefficient are in good agreement with the test results.Numerical analysis on T-shaped columns confined by stirrups under axial repeated compression loading was made by ANSYS software,the results show that the calculated rising segment of skeleton curve is in good agreement with the test curve;the error of peak load and peak strain between calculated value and experimental value is less than 10%;the calculated stress-strain curve of confined concrete is in good agreement with the test curve,the error of confined concrete strength between calculated value and experimental value is less than 10%,which prove the model made rational.Based on the test results and numerical analysis results,the confinement mechanism of the T-shaped column confined concrete was revealed,then the strength and deformability of confined concrete affected by reinforcement characteristic value,stirrup spacing,stirrup form and other factors was analyzed,the strength and strain formula of confined concrete was established,the calculated results are in good agreement with the test results.The stress-strain envelope curve formula for confined concrete of T-shaped columns under axial repeated loading was established referring to the stress-strain mathematical model for confined concrete of T-shaped columns under axial loading.The calculated curve is in good agreement with the experimental curve.Based on the analysis on loading and unloading curve of confined concrete,the loading and unloading formular was established,the calculated results are in good agreement with test results,which prove that the formular can describe the changing characteristics about the stress-strain curves of confined concrete when T-shaped columns confined by stirrups tested under axial repeated loading.