Abstract: Based on various compressive concrete strength tests under different pressures, empirical formulas for triaxial compressive strength, peak strain and stress-strain curves are presented and correlated those for uniaxial ones. Elasto-plastic analysis of concrete filled tubular steel (CFTS) stub columns is performed and theorefical formulas for elastic modulus and stress-strain curves of composite material of CFTS stub columns are presented. The calculated results are in good agreement with experimental results. It is believed that the results of the paper can be used in non-linear finite element analysis of CFTS columns.