Ultimate Resistance Design of Shuttle-Shaped Steel Tubular Latticed Columns

As a new type of nonprismatic built-up columns, the shuttle-shaped steel tubular latticed (SSTL) column is widely used in engineering structures. However, there are no methods available to test its ultimate resistance design and little research about its behavior. This article investigates the elastic buckling behavior of three-tube SSTL columns only with horizontal web members and subject to an axial load, and it is found that the SSTL column may buckle in a symmetric flexure-dominated mode or an antisymmetric shear-dominated mode, depending on distributions of sectional flexural stiffness and shear stiffness along the column length. The formulas for predicting elastic buckling loads are derived by accounting for the effects of sectional shear deformations. With the elastic buckling loads obtained, formulas for the effective slenderness and the normalized effective slenderness are proposed. The resistance design procedure for SSTL columns only with horizontal web members is developed in association with Chinese code GB50017 and Eurocode 3. Comparisons with finite element results demonstrate the proposed procedure can provide reasonably accurate predictions for the resistances of SSTL columns.