The Research On The Performance Of Cross-shaped Concrete Columns Confined By Stirrups Under Axially Repeated Loads

Special-shaped columns structure is a kind of new residential structure,which solved the problem of column's outer convex,it combined the beauty of building with the useing flexibility organically,and it provided users with a comfortable living condition.Compared with ordinary rectangular columns,Special-shaped columns structure has the poor seismic performance.We can effectively improve the seismic performance and brittleness of concrete through stirrups constraints on core concrete.The reasonable concrete material model is necessary for the nonlinear analysis of special-shaped column's deforming process,At present,scholars did researches on strength deformation and stress-strian curve of special-shaped columns confined by stirrups under axial loads,but study on special-shaped columns confined by stirrups under axially repeated loads is not available.It has a direct influence on intensity,ductility and resilience characteristics for seismic special-shaped columns structure by studying on the failure characteristics,deformation,strength properties and stress-strain curves of special-shaped columns structure under axially repeated loads.So we need to make research on the performance of cross-shaped concrete columns confined by stirrups under axially repeated loads.The strength,deformation and stress-strain relationship of confined concrete was Presented in order to give reference for the nonlinear analysis on the loading process and seismic behavior of special-shaped columns and structure,for the purpose of analyzing and designing special-shaped columns structure rationally.This paper has done researches on the failure process and characteristics of axially cross-shaped columns confined by stirrups under repeated loads on the basis of experiments.According to the test results,analyzing the relationship between ductility and reinforcement characteristic value,and established ductility factor formula for cross-shaped columns.Numerical analysis was made for axially cross-shaped columns confined by stirrups under repeated loads,and revealing the confinement mechanism of the cross-shaped concrete columns.On this basis,analyze the influence of the strength and deformation properties of confined concrete caused by stirrup amount,reinforcement characteristic value,stirrup spacing,stirrup form and other factors.Established the strength and strain formulas of cross-shaped columns confined by stirrups under axially repeated loads.The calculation results agreed well with text results.We established the stress and strain envelope curve formula for confined concrete of cross-shaped columns under axially repeated loads referring to the stress-strain mathematical model for confined concrete of cross-shaped columns under axially loads.The calculated curve is in good agreement with the experimental curve.Through the analysis of loading and unloading curve for cross-shaped concrete columns confined by stirrups under axially repeated loads,we established the loading and unloading curve equation,the calculation results agreed well with text results.It descripted that the curve equation can well reflect the change discipline about the stress-strain curves of cross-shaped concrete columns confined by stirrups under axially repeated loads.