Analytical properties of axially loaded lightweight aggregate concrete filled circular steel tubular stub columns

Based on the experimental results of mechanical properties of lightweight aggregate concrete filled circular steel tubular(LCFST) stub columns under axial compression,the axial stress-axial strain relations of concrete under axisymmetric triaxial compression were proposed.Based on continuum mechanics,the calculation model for LCFST stub columns of concentric cylinders of circular steel tube with concrete core under concentrically loaded conditions was determined.The theoretical calculation formulas for composite elastic modulus and composite stress-strain relations of the stub columns were presented.A FORTRAN program for the elasto-plastic analysis of LCFST stub columns under concentric loading was developed.The reliability of the present method and program was validated by the test results from references.The behavior of LCFST stub columns was analyzed.The analysis results indicated that for confinement by steel tube,the axial stress of lightweight aggregate concrete core increased greatly and the ductility was improved,while the axial stress of steel tube decreased rapidly for confinement effect.Compared with normal concrete filled circular steel tubular(CFST) stub columns,the confinement effect of LCFST stub columns was weakened.Through parameters analysis,a practical calculation formula for the bearing capacity and the composite stress-strain relations of LCFST stub columns were obtained.The analysis results consistent with the experiment ones from references.