Ultimate bearing capacity of asymmetrically double tapered steel columns with tubular cross-section

• Explicit formulas are derived to calculate the critical load of the columns.
• A method to predict ultimate bearing capacity of the columns under axial load
• A P–M interaction formula for predicting in-plane strength of the columns

As a new kind of non-uniform member, the asymmetrically double tapered column with tubular cross-section is composed of two tapered parts with different lengths. This kind of column is more effective and economic to resist combination of axial load and transverse load, with both its ends hinged and transverse load applied at the largest cross-section. Some classic non-uniform members such as stepped or tapered members have been investigated thoroughly, but there is not any available design method for asymmetrically double tapered columns so far. In this study, the elastic buckling behaviors of asymmetrically double tapered columns with solid circular and tubular cross-section are studied respectively. Bessel functions and fitting processes are used to derive explicit formulas of the critical load. Subsequently, the ultimate bearing capacity of asymmetrically double tapered tubular columns subject to axial load is studied. And the results obtained by the design formula proposed herein correlate well with these obtained by using finite element numerical analysis. Finally, a P–M interaction formula for predicting in-plane strength of double tapered tubular columns under axial load and uniaxial bending is suggested. Employment of a detailed nonlinear finite element analysis demonstrates the accuracy of the interaction formula.