Analysis of Axial Bearing Capacity for Dumbbell Shaped Concrete-filled Steel Tubular Stub Columns with Initial Stress

Based on four calculation methods of ultimate bearing capacity for dumbbell shaped concrete-filled steel tubular(CFST) columns without initial stress,and through importing initial stress reduction factor,the calculation formulas of the axial ultimate bearing capacity for dumbbell shaped CFST stub columns with initial stress were deduced with consideration of the influence of initial stress.According to the twin-shear unified strength theory,which considered the influence of intermediate principal stress and the strength-differential of materials,a new calculation method was proposed.Through comparing the calculation results with the experiment data for various calculation methods,the rationality of the proposed formula was proved and the basic characteristics of each method were expatiated as well.The result is of great significance to practical engineering application.